Miscellany

Jai Ganesh · 2019-04-22 00:15:26

330) Electromagnet

Electromagnet, device consisting of a core of magnetic material surrounded by a coil through which an electric current is passed to magnetize the core. An electromagnet is used wherever controllable magnets are required, as in contrivances in which the magnetic flux is to be varied, reversed, or switched on and off.

The engineering design of electromagnets is systematized by means of the concept of the magnetic circuit. In the magnetic circuit a magnetomotive force F, or Fm, is defined as the ampere-turns of the coil that generates the magnetic field to produce the magnetic flux in the circuit. Thus, if a coil of n turns per metre carries a current i amperes, the field inside the coil is ni amperes per metre and the magnetomotive force that it generates is nil ampere-turns, where l is the length of the coil. More conveniently, the magnetomotive force is Ni, where N is the total number of turns in the coil. The magnetic flux density B is the equivalent, in the magnetic circuit, of the current density in an electric circuit. In the magnetic circuit the magnetic equivalent to current is the total flux symbolized by the Greek letter phi, ϕ, given by BA, where A is the cross-sectional area of the magnetic circuit. In an electric circuit the electromotive force (E) is related to the current, i, in the circuit by E = Ri, where R is the resistance of the circuit. In the magnetic circuit F = rϕ,where r is the reluctance of the magnetic circuit and is equivalent to resistance in the electric circuit. Reluctance is obtained by dividing the length of the magnetic path l by the permeability times the cross-sectional area A; thus r = l/μA, the Greek letter mu, μ, symbolizing the permeability of the medium forming the magnetic circuit. The units of reluctance are ampere-turns per weber. These concepts can be employed to calculate the reluctance of a magnetic circuit and thus the current required through a coil to force the desired flux through this circuit.

Several assumptions involved in this type of calculation, however, make it at best only an approximate guide to design. The effect of a permeable medium on a magnetic field can be visualized as being to crowd the magnetic lines of force into itself. Conversely, the lines of force passing from a region of high to one of low permeability tend to spread out, and this occurrence will take place at an air gap. Thus the flux density, which is proportional to the number of lines of force per unit area, will be reduced in the air gap by the lines bulging out, or fringing, at the sides of the gap. This effect will increase for longer gaps; rough corrections can be made for taking the fringing effect into account.

It has also been assumed that the magnetic field is entirely confined within the coil. In fact, there is always a certain amount of leakage flux, represented by magnetic lines of force around the outside of the coil, which does not contribute to the magnetization of the core. The leakage flux is generally small if the permeability of the magnetic core is relatively high.

In practice, the permeability of a magnetic material is a function of the flux density in it. Thus, the calculation can only be done for a real material if the actual magnetization curve, or, more usefully, a graph of μ against B, is available.

Finally, the design assumes that the magnetic core is not magnetized to saturation. If it were, the flux density could not be increased in the air gap in this design, no matter how much current were passed through the coil. These concepts are expanded further in following sections on specific devices.

Solenoids.

A solenoid is generally a long coil through which current is flowing, establishing a magnetic field. More narrowly, the name has come to refer to an electromechanical device that produces a mechanical motion on being energized with an electric current. In its simplest form it consists of an iron frame enclosing the coil and a cylindrical plunger moving inside the coil. For an alternating current supply, the iron losses in a solid frame restrict the efficiency and a laminated frame is used, which is made up of a pile of thin sheets of iron cut to the appropriate shape and stacked with a layer of insulating varnish between each sheet. When the coil is energized, the plunger moves into the coil by virtue of the magnetic attraction between it and the frame until it makes contact with the frame.

Alternating-current solenoids tend to be more powerful in the fully open position than direct-current units. This occurs because the initial current, high because of the inductance of the coil, is lowered by the air gap between the plunger and frame. As the solenoid closes, this air gap decreases, the inductance of the coil increases, and the alternating current through it falls. If an alternating-current solenoid sticks in the open position the coil is likely to burn out.

When a solenoid is fully opened, it has a large air gap, and the high reluctance of this gap keeps the flux in the magnetic circuit low for a given magnetomotive force, and the force on the plunger is correspondingly low. As the plunger closes, the reluctance falls and the flux increases so that the force increases progressively. Manufacturers of solenoids provide force-stroke curves so that users can select the proper unit for their purpose. The curve can be modified by spring loading the plunger so that the force provided throughout the stroke may be matched to the particular mechanical load.

Relays.

A relay is a device in which the solenoid principle is applied to opening and closing light-current electrical circuits. The same device applied in heavy-current circuits is called a contactor, or circuit breaker.

Because the amount of mechanical movement required is generally small, the solenoid plunger is usually stationary, and part of the frame is hinged to give the necessary movement. When the coil is energized, the hinged part of the frame is attracted to the solid iron core in the coil; this attraction pushes the contacts together. When the energizing current is removed, the hinged part is forced back to the open position by the springiness of the contact.

With the appearance of transistorized switching circuits, which use remarkably low power, a need arose for a relay that would operate reliably with a power of 100 to 300 milliwatts, compared with 4 watts for the conventional relay. This need was met by the reed relay, or reed switch. It consists of two flat blades of 50–50 nickel–iron alloy that overlap with a gap between them. When a magnetic field is applied along the length of the blades, opposite magnetic poles are induced in the overlapping parts, and they are attracted together, making electrical contact. On removal of the field, the springiness of the contact blade opens the contact. The overlap region is plated on each blade with gold to ensure good electrical contact, and the enclosing glass capsule is filled with dry nitrogen to prevent corrosion. The field required to operate the device is a function of the amount of overlap, and there is an optimum overlap corresponding to minimum required operating current.

Present reed switches used in telephone equipment are operated by up to 50 volts direct current. Typically, the reed closes at 58 ampere-turns and releases at 15 ampere-turns, the hold current being 27 ampere-turns. The contact closes to give a stable contact resistance in 2 milliseconds, releases in 100 microseconds, and has a lifetime of more than 50,000,000 operations. Using a 35,000 turn coil the coil resistance is typically 18,600 ohms so that the current at 50 volts is 2.7 milliamperes. The minimum operating condition requires only about 1.7 milliamperes, so that the relay can be worked satisfactorily at lower voltage.

By the use of small, external, permanent magnets, reed switches can be made into latching relays that remain closed when the energizing field is removed. They can also be designed with three blades to give changeover contacts.

Design Of Large Electromagnets.

Sooner or later almost every scientific research laboratory finds that it requires a facility for producing large magnetic fields. A number of advanced technologies likewise require large electromagnets. A cyclotron, for example, is a device used for scientific research in which subatomic charged particles are accelerated by an alternating electric field in a constant magnetic field. It uses a large magnet to produce moderate fields but with a pole diameter that may be several metres. Some industries make use of huge, high-powered electromagnets for lifting purposes.

The basic design principles of large electromagnets are those discussed earlier. The difficulties arise in trying to estimate the magnitude of the fringing flux across the air gap and the leakage flux around the coils. Their effects are minimized by using a tapered shape for the cores and pole caps. Because soft iron saturates at 2.16 webers per square m, flux densities in the air gap are generally limited to the region of 2.1 webers per square m with iron magnets.

When designed for lifting or load-carrying purposes, an electromagnet may be required to have a single exposed pole face to which the load to be carried will attach itself, and it will therefore have the shape of a bar magnet. The design is then dominated by the demagnetizing field. Suitably designed magnets can lift many times their own weight and are in general use in steelworks and scrapyards.

Principal Applications

Electromagnets have a wide variety of uses. A summary of the principles of operation of some of the important devices in a few major areas of application—communications, research, electrical industry, and magnetic recording.

Modern telephone systems are based on the reed relay, together with solid-state circuits for complex routing of connections. The telephone receiver is basically an electromagnet with a U-shaped yoke having coils wound on each leg of the U. Passage of the electrical signal through the coils causes magnetic attraction of a soft-iron diaphragm supported a small distance from the ends of the U. The diaphragm is deflected by an amount proportional to the magnitude of the current in the coil and generates sound waves as it moves back and forth. Improvement in magnetic materials has increased the sensitivity of the telephone receiver, but the basic design has remained unchanged.

The loudspeaker performs the same function as the earphone of the telephone receiver but is required to displace a larger volume of air. The diaphragm comprises a flexible cone of large area carrying a coil of fine wire on a small ring located at its apex. The ring lies between the poles of a powerful cylindrically shaped permanent magnet. Audio-frequency current through the coil causes deflection of the diaphragm, as in the earphone. Modern loudspeakers are much more sensitive and efficient than their predecessors because of the improvement in permanent-magnet materials. The higher the flux density in the gap, the greater the sensitivity and the potential for fidelity of reproduction; modern loudspeakers use flux densities of up to one weber per square m. Alloy magnets are usually used.

Magnetic fields supply a powerful research tool without which modern physics could scarcely have grown to its present extent. A major area of application is in the interaction of magnetic fields and charged subatomic particles. A moving particle that carries a charge, such as an electron, can be regarded as an electric current and, like a current-carrying wire, experiences a force in a magnetic field. The direction of the force is perpendicular both to the direction of motion of the particle and to the magnetic field, so that the particle is deflected from its original path. This principle can be used to focus a stream of electrons into a narrow beam and to deflect the beam by creating suitable magnetic fields, either from permanent magnets or from electromagnets. Every television receiver contains just such focusing and deflection systems to scan the face of the television tube with an electron beam.

In scientific applications the same principle is used in the electron microscope, in which the beam of electrons is passed through a series of magnetic “lenses,” just as light is passed through glass lenses in a conventional microscope.

As noted above, the cyclotron makes use of a magnetic field to cause charged particles to execute a circular path. On each traverse of the circle they are accelerated and finally acquire enormous kinetic energy(energy of motion). The cyclotron has been an important tool in nuclear research and in the production of radioactive isotopes.

The same principle may be used to analyze materials in the mass spectrometer. The actual deflection of a moving charged particle in a magnetic field is determined by its charge, mass, and velocity. In a mass spectrometer the material under investigation is in the form of a gas of ionized particles that are accelerated by a fixed electric field. In passing through the magnetic field the particles are deflected by an amount determined by their mass, providing they all carry the same charge. By recording their arrival position at a fixed target, the mass of the particles can be deduced.

The electrical industry is founded on the generation and exploitation of magnetic fields. The electric motor is based on the force generated on a current-carrying conductor; the generator is based on the inverse effect that a conductor moving in a magnetic field has a current induced in it. In general, high-flux densities are required in the magnetic circuits of motors and generators, and this requirement has led to the use of soft iron or silicon–iron electromagnets as the source of magnetic fields in them. With the advent of modern permanent-magnet materials, however, small direct-current motors, in which the field is provided by permanent magnets, are finding wide applications, particularly in the toy industry.

The principle of magnetic recording is to induce a permanent magnetization in a material by means of the signal to be recorded. The induced magnetization must be proportional to the amplitude of the signal and must remain in the material when the signal is removed. Thus, a magnetic material is required that has a high permeability, so that it will magnetize readily in a small field; a high remanent magnetization, so that the stored information can be easily “read”; and not too high (but not too low) a coercive force, so that the stored information can be erased without great difficulty.

The most common type of magnetic recorder makes use of a magnetic tape. This passes at constant speed close to a recording head that may consist of a U-shaped magnet yoke with coils wound on each limb. As the current in the coil varies in accordance with the audio-frequency signal to be recorded, a varying magnetization is induced in the tape. To play back the recorded information, the tape is passed through or near a coil so that the magnetic flux from the tape cuts the wires of the coil and induces an audio-frequency current in it. The tape may be erased by passing it through a recording head that carries a high-frequency signal, which has the effect of demagnetizing the tape.

Computer information is in a particularly simple form for magnetic storage because it consists of a chain of electrical pulses of standard amplitude. Material requirements for the tape are not so stringent as for audio recording, the important feature being only that the tape should not demagnetize spontaneously. Many computers have replaced tape storage by discs of magnetic alloy that rotate under the recording head. Information can be stored at a higher density (bits per unit area) than in tape, and access to the information can be made faster by traversing the “read” head in a radial direction across the discs.

Jai Ganesh · 2019-04-24 00:06:43

331) Otter

Otter, (subfamily Lutrinae), any of 13 or 14 species of semiaquatic mammals that belong to the weasel family (Mustelidae) and are noted for their playful behaviour. The otter has a lithe and slender body with short legs, a strong neck, and a long flattened tail that helps propel the animal gracefully through water. Swimming ability is further enhancedin most species by four webbed feet. Two species are marine, with the others living predominantly in fresh water. Otters range in size from 3 kg (6.6 pounds) in the Asian small-clawed otter (Aonyx cinereus, formerly Amblonyx cinereus) to 26 kg (57 pounds) in the giant otter (Pteronura brasiliensis) and 45 kg (99 pounds) in the sea otter (Enhydra lutris). Furcolour is various shades of brown with lighter underparts.

Freshwater Otters

The 11 species often referred to as river otters are found throughout North America, South America, Europe, Africa, and Asia in freshwater ecosystems that sustain an abundance of prey such as fish, crayfish, crabs, mussels, and frogs. Most river otters are opportunistic, feeding on whatever is most easily obtained. Diet often varies seasonally or locally, depending on which prey is available. River otters hunt visually while chasing fish, but they use their manual dexterity to dislodge crabs and crayfish from under rocks. Sensory hairs on the snout called vibrissae also assist by sensing water turbulence. After being captured in the teeth or forefeet, prey is consumed either in the water or on shore. River otters hunt more effectively in shallow water than in deep water, and, although they are proficient swimmers, all prefer slow-swimming species of fish. African clawless otters (Aonyx capensis) and Congo clawless otters (A. congicus or A. capensis congicus) occupy murky waterways and thus rely more on manual dexterity than on vision to obtain food (mostly crabs) from under rocks. Their front feet are hand like and partially webbed.

Most travel is aquatic, but river otters can venture swiftly overland between bodies of water. They typically follow the shortest route possible and often establish much-used trails. While in the water, they constantly search features such as logjams and deepwater pools for prey. To rest, otters seek refuge in underground holes, rock crevices, beaver lodges, cavities in root systems, or simply dense vegetation along the shoreline. When not resting or eating, river otters can often be seen eagerly sliding down mud or snow banks. Many species establish regular latrine sites along the shores of lakes or rivers. Such stations may facilitate communication between individuals.

Litter size ranges from one to five. Young otters (pups) may fall prey to large raptors, and various carnivores may kill adults traveling on land. In warmer regions crocodiles and alligators are threats. However, most mortality results from human activities, in the form of road kills, drownings in fishnets, destruction as pests around fishing areas, or trapping for their fur.

Saltwater Otters

Two otter species are strictly marine: the sea otter (Enhydra lutris) of the Pacific Coast of North America and the much smaller marine otter (Lontra felina) from the coast of Peru and Chile. Both rely exclusively on marine prey, although the sea otter can be found much farther offshore; the marine otter stays within about 100 metres (330 feet) of the shore.

Sea otters are well adapted to marine life. The front and back feet are fully webbed; large lungs allow long dives and provide buoyancy and thick fur provides insulation. Sea otters can also drink salt water and thus can remain at sea for several days at a time. Sea otters are usually solitary but are sometimes seen in groups—gatherings of up to 2,000 have been observed along the coast of Alaska. At night, sea otters may choose either to sleep on land or simply to rest afloat near beds of kelp. They feed mainly on sea urchins, crabs, and various shellfish. Fish are also eaten. Captured prey is eaten at sea while the otter swims on its back. Rocks are typically used to break open crabs and shellfish, whereas sea urchins are crushed with the forefeet and teeth. Sea otter predation on the herbivorous urchins (genus Strongylocentrotus) enables kelp forests and the fish associated with them to flourish. However, large numbers of sea otters can deplete shellfish populations, conflicting with fisheries for crabs, clams, and abalones. Females give birth in water to only one young, which remains dependent on the mother until six to eight months of age. Sharks and killer whales eat sea otters on occasion.

The marine otter is really a freshwater otter that has learned to occupy marine environments in South America. This small (3–6 kg [6.6–13.2 pounds]) otter occurs on the Pacific coast from Peru through Chile and Tierra del Fuego in Argentina. It is mostly solitary, and only rarely do groups of more than three animals occur. Marine otters occupy the intertidal zone that covers the first 100–150 metres (roughly 330–500 feet) of coastal water and about 30 metres (100 feet) inland. They feed on crustaceans such as crabs and shrimp, as well as mollusks and fish. Interestingly, marine otters do not consume sea urchins as extensively as do sea otters, even though sea urchins often are common where marine otters live. Unlike sea otters, marine otters shelter in rock cavities for daytime rest and parturition.

Conservation And Classification

Nearly all species of otters face increasing threat as urbanization and logging continue. North American river otters (L. canadensis) are still taken as part of the commercial fur trade, but the primary threats to others are the destruction of wetland habitats and pollution. Heavy metals and contaminants such as mercury and PCBs accumulate in otter tissues and in time impair both reproduction and survival. Pollution also affects fish populations on which otters often depend. Conservation of remaining wetlands and restoration of water quality are currently the most important steps toward ensuring the future of otters.

Most authorities maintain that 13 species of otters make up the subfamily Lutrinae. The status of the Congo clawless otter remains a subject of debate, however, with most researchers considering the animal to be a subspecies of the African small-clawed otter (Aonyx capensis) and giving it the taxonomic name A. capensis congicus. Others claim that the Congo clawless otter is a valid species and have given it the taxonomic name A. congicus.

Sea otter

Sea otter, (Enhydra lutris), also called great sea otter, rare, completely marine otter of the northern Pacific, usually found in kelp beds. Floating on its back, it opens mollusks by smashing them on a stone balanced on its chest. The large hind feet are broad and flipperlike. It is 40–65 inches (100–160 cm) long and weighs 35–90 pounds (16–40 kg). The thick lustrous coat is reddish to dark brown. By 1910 it had been hunted almost to extinction for its fur; now fully protected, it is gradually increasing in numbers.

Jai Ganesh · 2019-04-26 00:08:53

332) Adipose Tissue

Adipose tissue, or fatty tissue, connective tissue consisting mainly of fat cells (adipose cells, or adipocytes), specialized to synthesize and contain large globules of fat, within a structural network of fibres. It is found mainly under the skin but also in deposits between the muscles, in the intestines and in their membrane folds, around the heart, and elsewhere. It is also found in the bone marrow, where it imparts a yellow colour; yellow marrow is most abundant in adults. The fat stored in adipose tissue comes from dietary fats or is produced in the body.

Mammals have two different types of adipose: white adipose tissue and brown adipose tissue. White adipose, the most common type, provides insulation, serves as an energy store for times of starvation or great exertion, and forms pads between organs. When muscles and other tissues need energy, certain hormones bind to adipose cells and trigger the hydrolysis of triacylglycerol, resulting in the release of energy-rich fatty acids and glycerol—a process known as lipolysis. The enzyme responsible for hydrolysis is lipase, which occurs in the blood, certain gastrointestinal juices, and adipose tissue. Lipase is activated by the hormones epinephrine, norepinephrine, glucagon, and adrenocorticotropin, which bind to adipocytes.

White adipose tissue also is a source of a number of different hormones, which serve various roles in metabolism and endocrine function. The adipose-produced hormones adiponectin, leptin, and resistin are involved in energy metabolism, for example, whereas plasminogen activator inhibitor-1 prevents the dissolution of blood clots.

Brown adipose, found mainly in newborn animals, generates heat and actually consumes energy. In humans, the percentage of brown adipose found in the body decreases with age. In other animals, however, particularly those that hibernate (e.g., grizzly bears and black bears), it is found in adults and plays an important role in survival. Species that hibernate experience a drop in body temperature and a slowing of metabolism during winter dormancy, which allows them to conserve energy. Brown adipose, by consuming energy, releases heat, which is vital for awakening and emergence from dormancy. Brown adipose tissue typically is tan to red in colour. Its colour and heat-generating properties are imparted by the abundance of organelles known as mitochondria found in brown fat cells. (Mitochondria are the energy-producing components of cells.)

In humans, the distribution of adipose tissue in the body can vary depending on gender. In general, men accumulate fat around the waist, and women tend to accumulate more fat around the hips than the waist. Geneticists have located distinct regions in the human genome that are associated with fat distribution, and several genes in particular appear to have a greater influence on waist-to-hip ratio in women than in men. Because these genes are involved in regulating the activities of fat cells, knowledge of their precise functions could provide insights into the biological mechanisms underlying obesity, diabetes mellitus, and cardiovascular disease.

Jai Ganesh · 2019-04-28 00:19:34

333) Carrot

Alternative Title: Daucus carota

Carrot, (Daucus carota), herbaceous, generally biennial plant of the Apiaceae family that produces an edible taproot. Among common varieties root shapes range from globular to long, with lower ends blunt to pointed. Besides the orange-coloured roots, white-, yellow-, and purple-fleshed varieties are known.

Wild carrot (subspecies D. carota carota, also called Queen Anne’s lace) is native to Eurasia and is thought to have been domesticated in Central Asia around 1000 CE. Prehistoric seeds have been found in archaeological digs, suggesting that the plant was used medicinally before the domestication of its edible root. Carrots were cultivated in China and northwestern Europe by the 13th century, and wild carrot was unintentionally distributed as a weed in the United States during European colonization. Domesticated carrots (subspecies D. carota sativus) are now extensively grown throughout temperate zones. In the 20th century, knowledge of the value of carotene(provitamin A) increased appreciation of the carrot, a rich source of the nutrient.

The plants require cool to moderate temperatures and are not grown in summer in the warmer regions. They require deep, rich, but loosely packed soil. Modern machines sow the seeds sparsely in bands to give room for plant development without need for thinning. An erect rosette of doubly compound, finely divided leaves develops above ground normally in the first season. The edible carrot and attached roots are below. If left unharvested, the plant survives through the winter, and large branched flower stalks arise the following growing season. The tiny white or pinkish flowers are borne on large compound clusters (umbels) at the ends of the main stalk and branches. The spiny seeds are produced in small segmented fruits called schizocarps. Seeds that are sold for planting have the spines removed.

Fresh carrots should be firm and crisp, with smooth and unblemished skin. Bright-orange colour indicates high carotene content; smaller types are the most tender. Carrots are used in salads and as relishes and are served as cooked vegetables and in stews and soups.

Monox D. I-Fly · 2019-04-28 19:31:50

ganesh wrote:

Besides the orange-coloured roots, white-, yellow-, and purple-fleshed varieties are known.

There are purple carrots?

Jai Ganesh · 2019-04-28 20:53:06

Yes, there are.

Here of carrots of different colors.

Monox D. I-Fly · 2019-04-29 14:27:58

Wow, there are 5 colors! Waiting for a carrot-themed Super Sentai.

Jai Ganesh · 2019-04-29 16:45:54

Monox D. I-Fly wrote:

Wow, there are 5 colors! Waiting for a carrot-themed Super Sentai.

Had to lookup!

Monox D. I-Fly · 2019-04-29 20:45:03

ganesh wrote:

Monox D. I-Fly wrote:
Wow, there are 5 colors! Waiting for a carrot-themed Super Sentai.
Had to lookup!
https://1.bp.blogspot.com/__AxBGnutuW8/S0ijfTBdDgI/AAAAAAAAF6k/7waez5Ff4PU/s320/DAI-RANGERS.JPG

Ever heard of Power Rangers? Super Sentai is its source material.

Jai Ganesh · 2019-04-30 00:06:44

334) Crow

Crow, (genus Corvus), any of various glossy black birds found in most parts of the world, with the exception of southern South America. Crows are generally smaller and not as thick-billed as ravens, which belong to the same genus. A large majority of the 40 or so Corvus species are known as crows, and the name has been applied to other, unrelated birds. Large crows measure about 0.5 metre (20 inches) long, with wingspans that can reach 1 metre (39 inches).

Crows feed chiefly on the ground, where they walk about purposefully. They are omnivores that enjoy meat and may even attack and kill young, weak animals. This habit makes them unpopular with farmers, as does the bird’s propensity to raid grain crops. Berries, insects, the eggs of other birds, and carrion are also eaten. Crows will make off with shreds of roadkill and store tidbits in trees, cachingthe meat like a leopard does for later consumption. Sometimes they bury seeds or store them in crevices in bark. They occasionally steal food from other animals, sometimes cooperating with other crows to raid food from otters, vultures, and water birds.

Crows live in large, close-knit families, and, like social mammals, they not only hunt and forage together but also defend territories and care for the young together. Most species, however, do not nest in colonies. Each mating pair has its own nest of sticks and twigs, usually high up in a tree. There are laid five or six greenish-to-olive eggs, with darker speckles. Young crows may spend up to six years with their parents before breeding on their own. As winter approaches, northern crows gather into large night-roosting groups. These flocks can include tens of thousands of birds and occasionally hundreds of thousands. Possible reasons for this seasonal gregariousness are warmth, protection against predators such as owls, or information exchange. A crow may live 13 years in the wild and more than 20 years in captivity.

Highly intelligent, crows can be masterful mimics. They have been trained to count aloud up to seven, and some crows have learned more than 100 words and up to 50 complete sentences; others have been known to mimic their owners’ voices in order to call dogs and taunt horses. They also exhibit great curiosity, fueling a reputation as inventive pranksters and calculating thieves. They fly off with people’s mail, pull clothespins off lines, and make off with unattended objects such as car keys. Two species—the New Caledonian crow (C. moneduloides) and the ‘alalā, or Hawaiian crow (C. hawaiiensis)—use stick-type foraging tools to obtain food from small holes and crevices. Such sophisticated tool use is only practiced by a handful of animal species.

Some common crows are the American crow (C. brachyrhynchos) of North America and the carrion crow (C. corone) of Europe and most of Asia. A subspecies of the carrion crow with gray on the back of the neck and breast is called the hooded crow (C. corone cornix). Sometimes considered a separate species, it is found between western Europe and eastern Asia and in the northern British Isles. Other crows include the house crow (C. splendens) of the Indian subcontinent (introduced in eastern Africa); the pied crow (C. albus), with white nape and breast, of tropical Africa; and the fish crow (C. ossifragus) of southeastern and central North America. Other members of the genus Corvus not called crows are the raven, jackdaw, and rook.

For birds in other families that are sometimes called crows, see currawong, or piping-crow; drongo, or king crow; kokako, or wattled crow; and rockfowl, or bald crow.

(a) Currawong, also called piping-crow, or crow-shrike, any of several songbirds of the Australian family Cracticidae (order Passeriformes). They are large, up to 50 centimetres (20 inches) long, with black, gray, or black-and-white plumage and yellow eyes. All have resounding, metallic voices. Found in woodlands and occasionally flocking into suburban areas, currawongs live on fruit, insects, small animals, and other birds’ eggs and young: they may be a nuisance in orchards and hen yards. The pied currawong, or chillawong (Strepera graculina) makes rolling sounds; the gray currawong (S. versicolor), also called squeaker, or rainbird, makes clanking noises.

(b) Drongo, any of approximately 26 species of Old World woodland birds constituting the family Dicruridae (order Passeriformes). Drongos frequently attack much larger birds (e.g., hawks and crows) that might hurt their eggs or young; innocuous birds (such as doves and orioles) nest near drongos to gain protection.

Most drongos are 18 to 63.5 cm (7 to 25 inches) long and glossy black, sometimes with white on the head or underparts (sexes alike); the eyes, in most, are fiery red. Some are crested or have head plumes, and the tail is usually long and forked, with outturned corners. The tail of the Southeast Asian racket-tailed drongo (Dicrurus paradiseus) bears 30-cm (12-inch) “wires”—outer feathers that are unbranched for most of their length and carry rather large
vanes at the ends.

Drongos range from Africa to Central Asia, Australia, and western Pacific islands, inhabiting forests, open country, and gardens. They feed like flycatchers or shrikes, taking large insects and termites. Their voices are loud mixtures of harsh and sweet sounds; some species, like the racket-tail, are good mimics. The nest is a flimsy basket that seems too small for the brooding bird.

One of the most common birds of southern Asia is the 33-cm (13-inch) black drongo (D. macrocercus), also called king crow because it can intimidate the true crow. The 24-cm (9.5-inch) African drongo (D. adsimilis; perhaps the same as D. macrocercus) is common throughout sub-Saharan Africa.

(c) Kokako, also called Wattled Crow, (species Callaeas cinerea), New Zealand songbird of the family Callaeidae (order Passeriformes). The kokako is 45 cm (17.5 inches) long and has a gray body, black mask, and blue or orange wattles at the corners of the mouth. Surviving in a few mountain forests, the kokako lives mainly on fruits and has a mellow, deliberate song; “organbird” and “bellbird” are local names.

(d) Rockfowl, also called Bald Crow, either of the two species of western African birds, genus Picathartes, constituting the subfamily Picathartinae, of uncertain family relationships in the order Passeriformes. Both species, with virtually no feathering on the head, have drab, grayish plumage and are thin-necked, hump-backed, and heavy-billed—quite vulture-like in appearance. In the white-necked rockfowl (Picathartes gymnocephalus), 48 centimetres (19 inches) long, found from Sierra Leone to Togo, the head skin is yellow and black; in the gray-necked rockfowl (P. oreas), 40 cm (15 1/2in.) long, of Cameroon, it is red and gray-blue. Rockfowl search the ground for insects, snails, crustaceans, and small vertebrates in wet, rocky upland forests. They make mud nests in colonies on cliffs.

Jai Ganesh · 2019-05-02 00:47:59

335) Mahogany

Mahogany (Swietenia mahogani) is a member of the family Meliaceae, which contains about 500 species of trees and shrubs native to tropical forests in the Americas, Africa, and Asia. Other common names for this species are the Spanish or West Indies mahogany. Various other species of trees have also been given the name mahogany, but the true mahogany is Swietenia mahogani. Mahogany is one of the most valuable of the tropical hardwoods because of its desirable qualities for the crafting of fine furniture.

Mahogany is native to humid tropical forests of the West Indies, Mexico, and Central America. Until rather recently, mahogany was especially abundant in forests in Honduras. However, the quantity of mahogany has been greatly reduced throughout its range by extensive logging. Although much reduced in abundance, mahogany is not yet considered an endangered species.

Mahogany is also indigenous to extreme southern Florida, where it occurs in some of the hardwood “islands” in the sawgrass wetlands of Everglades National Park, known locally as hammocks. However, mahogany reaches the northern limits of its range in southern Florida, and is rather sparse in that region. Because of its great value as lumber, mahogany has also been planted in suitable tropical climates beyond its native range.

Biology of mahogany

Mahogany grows as tall as about 66-98 feet (20-30 m), and can achieve a diameter of more than 24 inches (60 cm), exclusive of the large, basal buttresses the tree usually develops. Mahogany is a slow-growing tree, and it usually occurs in older, closed forests.

The wood of mahogany is very hard, heavy, and strong, and has a rich, red-brown color, with an attractive, crooked grain. Mahogany wood is among the world’s most prized and hardest-wearing timbers, and is principally used to manufacture fine furniture. The bark is dark brown and rather scaly.

Mahogony’s dark-green leaves of mahogany are arranged in an alternate fashion on the twigs. They are compound, meaning six to eight oval-shaped, leathery leaflets arise from a single petiole. The entire leaf has a length of 4-7 inches (10-18 cm). Mahogany leaves are evergreen, that is, they are not shed all at once at some particular season.

The flowers of mahogany are small, only about 0.1 inch (2-3 mm) in diameter, with five greenish or whitish petals occurring in open clusters as a loose inflorescence. The flowers secrete nectar and are pollinated by insects. The fruits of mahogany are a reddish-brown capsule, which when ripe, split along five seams to shed the 0.8 inch- (2 cm) long seeds.

Uses of mahogany

Mahogany wood is used to manufacture fine furniture; it is valued because it is durable and can be carved with intricate details. It has a deep, rich color, attractive grain, stains beautifully, and glues solidly onto manufactured products. Mahogany was first imported to Europe in 1724, and it soon became famous because of the gracefully ornate furniture that Thomas Chippendale, an English cabinetmaker, began to make from the wood.

The most valuable raw product produced from mahogany wood is solid lumber, which can then be manufactured into expensive furniture and cabinets. However, solid mahogany is a very expensive material, and is becoming increasingly difficult to obtain. As a result, much mahogany is now used to manufacture a veneer product, in which a core of inferior wood is covered with a thin layer of mahogany. This composite material is glued together, and combines many of the desirable qualities of mahogany, especially its beautiful grain and color, with the cost savings associated with the use of other, relatively inexpensive species of trees.

Some related species

Some other species in the family Meliaceae are of commercial importance as sources of lumber, or as ornamental plants in horticulture.

The Spanish or cigar-box cedar (Cedrela odorata ) of Central and South America has a hard, durable, richly colored wood that is used as a substitute for the true mahogany in fine cabinetry and furniture, as is the

Key Terms

Buttress —A structure that many trees of humid tropical forests grow at their base to stabilize the tree against the swaying forces of the wind. Buttresses can occur as broadened bases of the trunk, or as large, vertical projections from the base.

Tropical hardwood —A generic term for a wide variety of species of tropical trees. Tropical hardwoods have a heavy, dense wood that is valuable for the manufacturing of lumber, or composite materials such as plywood. Mahogany and teak are among the most prized of the tropical hardwoods.

Crabwood (Carapa guianensis), with a broadly similar range. African mahogany (Khaya senegalensis ) grows in tropical forests on the west coast of Africa and is one of the many African species, including those in the genera Entandrophragma and Lovoa, which are substituted for the wood of the true mahogany. Some tropical hardwoods in other plant families are also used as substitutes for mahogany, for example, the Columbian mahogany Cariniana pyriformis, family Lecythidaceae.

The Chinaberry (Melia azedarach ) is native to southern Asia, but is grown as an ornamental plant in parts of the southern United States. The compound leaves of the Chinaberry can be longer than 20 inches (50 cm), and its purplish flowers are attractive and fragrant.

Species in the genera Azadirachta and Melia are used to manufacture botanical insecticides. Seeds of the trees Carapa guianensis and C. moluccensis are used to manufacture a minor product known as carapa fat, a thick white or yellow oil used in oil lamps, and sometimes as an insect repellant.

Jai Ganesh · 2019-05-04 01:27:46

336) Hippopotamus

Hippopotamus, (Hippopotamus amphibius), also called hippo or water horse, amphibious African ungulate mammal. Often considered to be the second largest land animal (after the elephant), the hippopotamus is comparable in size and weight to the white rhinoceros (Ceratotherium simum) and the Indian rhinoceros (Rhinoceros unicornis).

Hippopotamus is Greek for “river horse,” and the animal has been known since ancient times. Hippopotamuses are often seen basking on the banks or sleeping in the waters of rivers, lakes, and swamps next to grasslands. Because of their great size and aquatic habits, they are safe from most predators but human beings, who have long valued their hide, meat, and ivory and at times have resented them for ruining crops. Once ranging over the entire continent and beyond, hippopotamuses (or “hippos”) now live in eastern, central, and parts of southern Africa.

General Characteristics

The hippopotamus has a bulky body on stumpy legs, an enormous head, a short tail, and four toes on each foot. Each toe has a nail-like hoof. Males are usually 3.5 metres (11.5 feet) long, stand 1.5 metres (5 feet) tall, and weigh 3,200 kg (3.5 tons). In terms of physical size, males are the larger gender, weighing roughly 30 percent more than females. The skin is 5 cm (2 inches) thick on the flanks but thinner elsewhere and nearly hairless. Colour is grayish brown, with pinkish underparts. The mouth is half a metre wide and can gape 150° to show the teeth. The lower canines are sharp and may exceed 30 cm (12 inches).

Hippos are well adapted to aquatic life. The ears, eyes, and nostrils are located high on the head so that the rest of the body may remain submerged. The ears and nostrils can be folded shut to keep out water. The body is so dense that hippos can walk underwater, where they can hold their breath for five minutes. Although often seen basking in the sun, hippos lose water rapidly through the skin and become dehydratedwithout periodic dips. They must also retreat to the water to keep cool, for they do not sweat. Numerous skin glands release an oily reddish or pinkish “lotion,” which led to the ancient myth that hippos sweat blood; this pigment actually acts as a sunblock, filtering out ultraviolet radiation.

Behaviour

Hippos favour shallow areas where they can sleep half-submerged (“rafting”). Their populations are limited by this “day living space,” which may become quite crowded; as many as 150 hippos may use one pool in the dry season. In times of drought or famine, they may embark on overland migrations that often result in many deaths. By night, hippos walk along familiar paths as far as 10 km (6 miles) into surrounding grasslands to feed for five or six hours. The long canines and incisors are used strictly as weapons; grazing is accomplished by grasping grass with the tough wide lips and jerking the head. Near the river, where grazing and trampling are heaviest, large areas may be denuded of all grass, which results in erosion. Hippos, however, eat relatively little vegetation for their size (about 35 kg [80 pounds] per night), as their energy requirement is low because they are buoyed in warm water much of the time. Hippos do not chew cud but retain food for a long time in the stomach, where protein is extracted by fermentation. Their digestive process cycles tremendous quantities of nutrients into the African rivers and lakes and thereby supports the fish that are so crucial as a protein source in the diet of the local people.

In the wild, females (cows) become sexually mature between ages 7 and 15, and males mature slightly earlier, between ages 6 and 13. In captivity, however, members of both genders may become physically mature as early as ages 3 and 4. Dominant bulls more than 20 years old, however, initiate most of the mating.

Bulls monopolize areas in the river as mating territories for 12 years or more. Subordinate males are tolerated if they do not attempt to breed. Cows aggregate in these areas during the dry season, which is when most mating takes place. Rare battles may erupt when strange bulls invade territories in the mating season. Most aggression is noise, splash, bluff charges, and a yawning display of the teeth, but opponents may engage in combat by slashing upward at each other’s flanks with the lower incisors. Wounds can be fatal despite the thick skin there. Adjacent territorial bulls will stare at each other, then turn, and, with rear end out of the water, flip feces and urine in a wide arc by rapidly wagging the tail. This routine display indicates that the territory is occupied. Territorial and subordinate males alike make dung piles along pathways leading inland, which probably function as olfactory signposts (scent markers) at night. Hippos recognize individuals by scent and sometimes follow one another nose-to-tail on night treks.

Fertilization results in a single calf weighing about 45 kg (99 pounds), born after a gestation of eight months. The calf can close its ears and nostrils to nurse underwater; it may climb onto its mother’s back above the water to rest. It begins to eat grass by one month and is weaned at six to eight months of age. Cows produce a calf every two years. Young calves are vulnerable to crocodiles, lions, and hyenas. It is thought that attacks on small boats are antipredator behaviour, with the hippos mistaking the boats for crocodiles. As a result, hippos have long had a largely undeserved reputation as aggressive animals. Cows live in “schools,” but they are not permanently associated with other cows, though sometimes they maintain bonds with offspring for some years. Longevity is up to 61 years in captivity but rarely more than 40 in the wild.

Distribution

Trampling and crop raiding by hippos led to early and determined efforts to exterminate them; their hides and meat were also valued. Hippos were extinct in northern Africa by 1800 and south of Natal and the Transvaal by 1900. They are still fairly common in East Africa, but populations continue to decrease continentwide. There remains a demand for hippo teeth as a fine-grained “ivory” that is easy to carve; it was once used to make false teeth. After the international elephant ivory ban went into effect in 1989, hunting pressure on hippos increased, and hippo populations declined. A population assessment performed in 2008 estimated that between 126,000 and 149,000 individuals remained.

Pygmy Hippopotamus

The rare pygmy hippopotamus (Hexaprotodon liberiensis, also known as Choeropsis liberiensis), the other living species of the family Hippopotamidae, is about the size of a domestic pig. The pygmy hippo is less aquatic than its larger relative, although, when pursued, it hides in water. Less gregarious, it is seen alone or with one or two others in the lowland tropical forests of Liberia, Côte d’Ivoire, Sierra Leone, and Guinea, along streams and in wet forests and swamps. Liberians call it a “water cow.” It eats some grasses and also fresh leaves of trees and bushes, herbs, and fallen fruits. The International Union for Conservation of Nature has classified the pygmy hippopotamus as endangered since 2006.

Evolution

Morphological comparisons have historically linked Hippopotamidae to pigs (family Suidae) and peccaries (family Tayassuidae). These groups diverged from other members of the order Artiodactyla about 45 million years ago, but molecular studies suggest that hippos and cetaceans(whales and dolphins) have an earlier common ancestor and may be more closely related. A fossil resembling today’s pygmy hippo dates to about 21 million years ago, in the Miocene Epoch (23 million to 5.3 million years ago). Hippos eventually reached Europe and Asia, though climate changes and overhunting by humans had exterminated all species outside Africa by the end of the Pleistocene Epoch (11,700 years ago). Three species lived on Madagascar until recent times; their extinction may have coincided with the arrival of humans about 1,000 years ago.

Jai Ganesh · 2019-05-06 01:16:48

337) Kangaroo

Kangaroo, any of six large species of Australian marsupials noted for hopping and bouncing on their hind legs. The term kangaroo, most specifically used, refers to the eastern gray kangaroo, the western gray kangaroo, and the red kangaroo, as well as to the antilopine kangaroo and two species of wallaroo. Less specifically, kangaroo refers to all 14 species in the genus Macropus, some of which are called wallabies. In its broadest usage, kangaroo refers to any member of the family Macropodidae, which comprises about 65 species, including tree kangaroos and the quokka; rat kangaroos are classified into “sister” familes, Potoroidae and Hypsiprymnodontidae. The Macropodidae are found in Australia (including Tasmania and other offshore islands, such as Kangaroo Island), New Guinea, and the islands east to the Bismarck Archipelago. Several species have been introduced into New Zealand.

Form And Function

Common features

With the exception of tree kangaroos (genus Dendrolagus), all members of the kangaroo family (Macropodidae) rely on long, powerful hind legs and feet for hopping and leaping, their predominant forms of locomotion. Their long tails, thickened at the base, are used for balancing. This feature is most obvious in the large kangaroos, which use the tail as a third leg when standing still. Each long, narrow hind foot has four toes, the large fourth toe bearing most of the animal’s weight. The second and third toes are united and merely vestigial, a condition known as syndactyly. The short forelimbs, having five unequal digits, are used almost like human arms, but all digits of the “hand” are sharp-clawed, and the thumb is not opposable. The head is relatively small; the ears are (in most macropodids) large and rounded; and the mouth is small, with prominent lips. The pelage is generally soft and woolly; in many species it is grizzled, and stripes may be present on the head, back, or upper limbs. All macropodids are herbivorous and have a chambered stomach that is functionally similar to those of such ruminants as cattle and sheep. Ecologically, they occupy the niche filled elsewhere by grazing and browsing animals (larger species tend to be grazers, smaller ones browsers). Several smaller species have become extinct or are gravely endangered, probably because of predation by introduced foxes. The wedge-tailed eagle (Aquila audax) is one of the macropodids’ few natural predators.

Reproduction and development

In all species, the marsupium (or pouch) is well developed, opens forward, and contains four teats. The young kangaroo (“joey”) is born at a very immature stage, when it is only about 2 cm (1 inch) long and weighs less than a gram (0.04 ounce). Immediately after birth, it uses its already clawed and well-developed forelimbs to crawl up the mother’s body and enter the pouch. The joey attaches its mouth to a teat, which then enlarges and holds the young animal in place. After continuous attachment for several weeks, the joey becomes more active and gradually spends more and more time outside the pouch, which it leaves completely at 7 to 10 months of age.

Female macropodids of many species enter into heat within a few days after giving birth, mating and conception thus occurring while the previous offspring is still in the pouch. After only one week’s development, the microscopic embryo enters a dormant state, called diapause, that lasts until the first joey begins to leave the pouch or until conditions are otherwise favourable. The development of the second embryo then resumes and proceeds to birth after a gestation period of about 30 days. Therefore, the teats are for a while feeding young of very different developmental stages, during which time different teats produce two different compositions of milk. This is thought to be an adaptation for recovering population numbers quickly after a drought, when breeding ceases and the diapause state is prolonged. In the gray kangaroos, which live in wooded country with a more predictable environment, this system does not exist; there is no diapause, and the pouch is occupied by one young at a time.

Dentition

The larger species of kangaroos have complex, high-crowned teeth. The four permanent molars on each side of both jaws erupt in sequence from front to back and move forward in the jaw, eventually being pushed out at the front. Thus, an old kangaroo may have only the last two molars in place, the first two (and the premolar) having long since been shed. The molars possess cross-cutting ridges, so that tough grass is sheared between opposing teeth. The molars of smaller macropodids are much simpler. The large kangaroos continue growing throughout life, especially the males (most markedly in the red kangaroo), whereas the smaller macropodids do not.

Behaviour

Kangaroos have an irregular activity rhythm; generally, they are active at night and during periods of low light, but it is quite possible to find them out in the open in bright sunlight. During hot weather, kangaroos lick their forearms, which promotes heat loss by evaporation. Kangaroos travel and feed in groups (“mobs”) whose composition shifts, but they are not truly social, since the individual members move at liberty. One member can send the mob into a wild rout - individuals bounding off in all directions - by thumping its tail on the ground in a signal of alarm. In any mob, the largest male (“old man,” or “boomer”) dominates during the mating season. Males fight for access to females by biting, kicking, and boxing. These methods are also used by kangaroos to defend themselves against predators. With their agile arms, they can spar vigorously. They can also use the forepaws to grip an enemy while rocking back on their tails and then swiftly dropping their huge clawed hind feet. This tactic has been known to disembowel dogs and humans. When chased by hunters with dogs, kangaroos often make for water, where they have been known to turn and press down on the dog with their forepaws in an attempt to drown it.

Overall, however, kangaroos have benefited from human presence. Aboriginal hunters regularly burned large areas of forest and grassland, opening up the country for large grazers at the expense of smaller browsers. European pastoralists then cleared further tracts of dense vegetation and provided permanent sources of water in arid and seasonal habitats. By the late 20th century, the number of kangaroos in Australia had increased to the point that a major industry came to be based on them. The three most abundant species, the eastern gray, western gray, and red kangaroos, together number in the tens of millions. Every year millions of these three species, and thousands of medium-size species such as whiptail wallabies (M. parryi), are harvested. Their skins are made into rugs and clothing, and their meat, formerly used as pet food, is now increasingly sold for human consumption. Kangaroos are also killed because they compete for forage with livestock. Other threats are feral dogs introduced to the Australian mainland.

Descriptions Of Selected Species

The eastern gray kangaroo (Macropus giganteus) is found mostly in the open forests of eastern Australia and Tasmania. It is replaced by the western gray kangaroo (M. fuliginosus) along the southern coast into the southwest of Western Australia. The ranges of the two species overlap in western New South Wales and western Victoria. Both species, but especially the eastern, prefer lightly forested country, at least for refuge, but they go out into the open plains for grazing. Western grays are stockier and more brownish; there are different subspecies in the southwest, on Kangaroo Island, and on the Nullarbor Plain. Each of these may in fact be distinct species. Eastern grays may grow up to 2.1 metres (6.9 feet) in length, and some males can weigh as much as 90 kg (about 200 pounds). In contrast, western grays are shorter, with an average length of 1.6 metres (5.25 feet), and some males can weigh up to 54 kg (about 120 pounds).

Gray kangaroos can clear more than 9 metres (30 feet) at a bound - 13.5 metres has been recorded—and can attain a speed of 55 km/hr (kilometres per hour; 34 mph [miles per hour]). Research has revealed a remarkable advantage to bipedal hopping. Although at low speeds kangaroos expend more energy than do quadrupeds of the same size, the red kangaroo (M. rufus) actually uses less energy at 10.1 km/hr than at 6.5 and less still at higher speeds. This seems to be related to the storage of elastic strain energy in its tendons and muscles. In addition, the heavy tail swings downward as the legs are moving backward, which helps to counteract the natural pitching motion of the head and upper body - another energy-saving device.

The red kangaroo is found throughout Australia’s interior grasslands and is the largest and most powerful macropodid. An old male may attain a head and body length of 1.5 metres (5 feet), have a tail 1 metre (3.3 feet) long, and stand 2 metres (6.6 feet) tall. Males can weigh 90 kg (200 pounds), but females are much smaller. Usually males are red and females are blue-gray, but there are generally a few red females and gray males in most populations. In regions such as western New South Wales, where red kangaroos and both species of grays can be found in the same general area, the red kangaroo is easily distinguished by its longer arms, convex face, whitish underparts, prominent black and white whisker marks on the muzzle, and bald patch on the nose (rhinarium). Gray kangaroos are more uniformly coloured, and the nose is haired.

The antilopine kangaroo (M. antilopinus), sometimes called the antilopine wallaroo, replaces the red kangaroo in the plains of the tropical north, from Cape York Peninsula in the east to the Kimberleys in the west. It is smaller than the red kangaroo and more wallaroo-like in general appearance, although it is more slenderly built. Males can grow to be 1.8 metres (5.9 feet) long and can weigh as much as 70 kg (154 pounds), whereas females are smaller, often weighing less than 30 kg (66 pounds).

The antilopine kangaroo is an extremely fast hopper. The wallaroo, or euro (M. robustus), is a smaller, stockier animal quite closely related to the red kangaroo and like it in that the genders are coloured differently (black in the male, reddish in the female), though this is not universal. The rhinarium is larger than in the red kangaroo. This wallaroo lives in hilly country throughout mainland Australia except in the far north, where it is replaced by the smaller Woodward’s, or black, wallaroo (M. bernardus).

Jai Ganesh · 2019-05-08 00:23:04

338) Domestic Cat

Felis catus has had a very long relationship with humans. Ancient Egyptians may have first domesticated cats as early as 4,000 years ago. Plentiful rodents probably drew wild felines to human communities. The cats' skill in killing them may have first earned the affectionate attention of humans. Early Egyptians worshipped a cat goddess and even mummified their beloved pets for their journey to the next world—accompanied by mummified mice! Cultures around the world later adopted cats as their own companions.

Hunting Abilities

Like their wild relatives, domestic cats are natural hunters able to stalk prey and pounce with sharp claws and teeth. They are particularly effective at night, when their light-reflecting eyes allow them to see better than much of their prey. Cats also enjoy acute hearing. All cats are nimble and agile, and their long tails aid their outstanding balance.

Communication

Cats communicate by marking trees, fence posts, or furniture with their claws or their waste. These scent posts are meant to inform others of a cat's home range. House cats employ a vocal repertoire that extends from a purr to a screech.

Diet

Domestic cats remain largely carnivorous, and have evolved a simple gut appropriate for raw meat. They also retain the rough tongue that can help them clean every last morsel from an animal bone (and groom themselves). Their diets vary with the whims of humans, however, and can be supplemented by the cat's own hunting successes.

Domesticated Mammal

Cat, (Felis catus), also called house cat or domestic cat, domesticated member of the family Felidae, order Carnivora, and the smallest member of that family. Like all felids, domestic cats are characterized by supple low-slung bodies, finely molded heads, long tails that aid in balance, and specialized teeth and claws that adapt them admirably to a life of active hunting. Cats possess other features of their wild relatives in being basically carnivorous, remarkably agile and powerful, and finely coordinated in movement.

It is noteworthy that the ancestors of the other common household pet, the dog, were social animals that lived together in packs in which there was subordination to a leader, and the dog has readily transferred its allegiance from pack leader to human master. The cat, however, has not yielded as readily to subjugation. Consequently, the house cat is able to revert to complete self-reliance more quickly and more successfully than most domesticated dogs.

Origin And History Of Cats

The “cat pattern,” established very early in the evolution of modern mammals, was a successful one: early cats were already typical in form at a time when the ancestors of most other modern mammalian types were scarcely recognizable. They first appeared in the early Pliocene Epoch (5.3 to 3.6 million years ago), and they have continued with remarkably little change into modern times.

Domestication

Although the origin of the domesticated cat is hidden in antiquity, studies involving mitochondrial DNA (mtDNA) suggest that there have been two lineages of Felis catus. One lineage (F. silvestris silvestris) appeared in Asia Minor possibly as early as 6,400 years ago and dispersed northward and westward into Europe. The other lineage appeared in Egypt sometime between 6,400 and 1,000 years ago before spreading throughout the Mediterranean (possibly through humanintroduction) along paths that paralleled the region’s trade routes. Cats of both lineages continued to breed with the African wildcat (F. silvestris lybica) during their respective dispersals.

The earliest known association between cats and humans dates possibly as far back as the origins of agriculture in the Middle East, about 9,500 years ago. A cat skeleton accompanying that of a human dated to that time was discovered in southern Cyprus. Although some sources note that this finding suggests that cats had undergone some degree of domestication in that location, other sources (citing evidence that the cat genome did not differ that much from that of the African wildcat during this period) argue that cats may have domesticated themselves by choosing to live in human-altered landscapes. Fossil evidence found in China dating to approximately 5,300 years ago revealed that cats similar in size to modern domestic cats fed on small grain-eating animals, such as rodents, and millet in agricultural settings. Although research suggests that these cats were actually leopard cats (Prionailurus bengalensis), which were replaced by modern domestic cats (F. catus) before 3000 BCE, this discovery suggests that humans allowed cats to hunt mice and other rodents that threatened grain stores and possibly fed the cats or allowed them to consume leftover food.

Although the cat was proclaimed a sacred animal in Egypt in the 5th and 6th dynasties (c. 2465–c. 2150 BCE), it had not necessarily been domesticated at that time. It is probable that the ancient Egyptianspartnered with the cat because they realized its value in protecting granaries from rodents. Their affection and respect for this predator led to the development of religious cat cults and temple worship of cats. There are no authentic records of domestication earlier than 1500 BCE, however.

Cats have long been known to other cultures. Wall tiles in Crete dating from 1600 BCE depict hunting cats. Evidence from art and literatureindicates that the cat was present in Greece from the 5th century BCE, and tiles featuring cats appeared in China from 500 BCE. In India cats were mentioned in Sanskrit writings around 100 BCE, while the Arabs and the Japanese were not introduced to the cat until about 600 CE. The earliest record of cats in Britain dates to about 936 CE, when Howel Dda, prince of south-central Wales, enacted laws for their protection.

Even though all cats are similar in appearance, it is difficult to trace the ancestry of individual breeds. Since tabbylike markings appear in the drawings and mummies of ancient Egyptian cats, present-day tabbiesmay be descendants of the sacred cats of Egypt. The Abyssinian also resembles pictures and statues of Egyptian cats. The Persian, whose colouring is often the same as that of mixed breeds (although the length of hair and the body conformation are distinctive), was probably crossed at various times with other breeds. The tailless Manx cat, like the hairless Sphynx cat and curly-coated Devon Rex, is a mutation. The ancestry of Persian and Siamese cats may well be distinct from that of other domestic breeds, representing a domestication of an Asian wild cat. In fact, nothing is known of the ancestry of the Siamese types, and there is no living species of Asian cat that could have served as ancestor.

Associations with human culture

The cat has long played a role in religion and witchcraft. In the Bible, “cat” is mentioned only in the apocryphal Letter of Jeremiah. The cat figured prominently in the religions of Egypt, the Norse countries, and various parts of Asia. The Egyptians had a cat-headed goddess named Bast (or Bastet). Thousands of cat mummies have been discovered in Egypt, and there were even mouse mummies, presumably to provide food for the cats. Often the cat has been associated with sorcery and witchcraft, and the superstitions regarding cats are innumerable. Throughout the ages, cats have been more cruelly mistreated than perhaps any other animal. Black cats in particular have long been regarded as having occult powers and as being the familiars of witches.

The cat is a familiar figure in nursery rhymes, stories, and proverbs. The English legend of Whittington and his cat is a particular favourite. The writers Théophile Gautier and Charles Baudelaire paid it homage, and in the 20th century Rudyard Kipling, Colette, and T.S. Eliot wrote of cats, and British composer Sir Andrew Lloyd Webber created the popular stage production Cats.

General Features And Special Adaptations

The average weight of the household cat varies from 2.7 to 4.5 kg (6 to 10 pounds), although, among nonpedigreed cats, weights up to 12.7 kg (28 pounds) are not uncommon. Average lengths are 71.1 cm (28 inches) for males and 50.8 cm (20 inches) for females. In keeping with a carnivoroushabit, the cat has a simple gut; the small intestine is only about three times the length of the body.

The skin of the cat, composed of dermis and epidermis, regenerates and fights off infection quickly. Tiny erector muscles, attached to hair follicles, enable the cat to bristle all over. Thus, although the cat is a relatively small animal, it can frighten enemies by arching its back, bristling, and hissing.
Coordination and musculature

Cats are among the most highly specialized of the flesh-eating mammals. Their brains are large and well developed. Cats are digitigrade; that is, they walk on their toes. Unlike the dog and horse, the cat walks or runs by moving first the front and back legs on one side, then the front and back legs on the other side; only the camel and the giraffe move in a similar way. The cat’s body has great elasticity. Because the vertebrae of the spinal column are held together by muscles rather than by ligaments, as in humans, the cat can elongate or contract its back, curve it upward, or oscillate it along the vertebral line. The construction of the shoulder joints permits the cat to turn its foreleg in almost any direction. Cats are powerfully built animals and are so well coordinated that they almost invariably land on their feet if they fall or are dropped.

Teeth

The cat’s teeth are adapted to three functions: stabbing (canines), anchoring (canines), and cutting (molars). Cats have no flat-crowned crushing teeth and therefore cannot chew their food; instead, they cut it up. Except for the canines and molars, the cat’s teeth are more or less nonfunctional; most of the cheek teeth do not even meet when the mouth is closed. The dental formula in all cats, for either side of both upper and lower jaws, is incisors 3/3, canines 1/1, premolars 3/2, and molars 1/1. The total number of teeth is 16 in the upper jaw and 14 in the lower. Primary, or milk, teeth number 24; these are replaced by the permanent teeth at about five months. Each half of the jaw is hinged to the skull by a transverse roller that fits tightly into a trough on the underside of the skull, making grinding movements impossible even if the cat had teeth suitable for grinding.

Claws

There is a remarkable mechanism for retracting the cat’s claws when they are not in use. The claw is retracted or extended by pivoting the end bone of the toe, which bears the claw, over the tip of the next bone. The action that unsheathes the claws also spreads the toes widely, making the foot more than twice as broad as it normally is and converting it into a truly formidable weapon. This claw-sheathing mechanism is present in all species of the cat family except the cheetah. Although there are no nerve endings in the nail itself, blood capillaries are present in the inner part.

Senses

Cats are generally nocturnal in habit. The retina of the cat’s eye is made extra sensitive to light by a layer of guanine, which causes the eye to shine at night in a strong light. The eyes themselves, large with pupilsthat expand or contract to mere slits according to the density of light, do not distinguish colours clearly. Cats have a third eyelid, or nictitating membrane, commonly called the haw. Its appearance is used frequently as an indicator of the cat’s general state of health.

The cat’s sense of smell, particularly well developed in the adult, is crucial to its evaluation of food, so that a cat whose nasal passages become clogged as a result of illness may appear to lose its appetite completely. Cats can distinguish the odour of nitrogenous substances (e.g., fish) especially keenly.

The sense of touch is acute in cats. The eyebrows, whiskers, hairs of the cheek, and fine tufts of hair on the ears are all extremely sensitive to vibratory stimulation. The functions of the whiskers (vibrissae) are only partially understood; however, it is known that, if they are cut off, the cat is temporarily incapacitated. The toes and paws, as well as the tip of the nose, are also very sensitive to touch.

Cats also have an acute sense of hearing. Their ears contain almost 30 muscles (compared with 6 in humans); as a result, they can turn them many times more quickly in the direction of a sound than can a dog. The ears of cats are receptive to ultrasonic frequencies up to 85,000 vibrations per second, greatly exceeding the hearing capabilities of dogs, which register 35,000 vibrations per second.

Behaviour

Special traits

The cat has a subtle repertoire of facial expressions, vocal sounds, and tail and body postures that express its emotional state and intentions. These various signals serve to increase, decrease, or maintain social distance. One distinctive social behaviour involves rubbing the side of the head, lips, chin, or tail against the owner and against furniture. These regions of the cat’s body contain scent glands that seem to play a role in establishing a familiar odour in the cat’s environment.

The tongue of all cats, which has a patch of sharp, backward-directed spines called filiform papillae near the tip, has the appearance and feel of a coarse file; the spines help the cat to groom itself. The disposition to cleanliness is well established in cats, and they groom themselves at length, especially after meals.

While lions and other big cats roar, domestic cats and other Felis species purr. Purring has been described as a low, continuous, rattling hum and often is interpreted as an expression of pleasure or contentment. Purring also occurs in cats that are injured and in pain, however, so that this vocalization can be seen as the cat’s “mantra”—that is, as a relaxing, self-comforting sound and a friendly mood-conveying signal.

Behavioral problems

Under conditions of domestication, the cat is subject to a variety of factors that result in behaviour indicative of emotional distress and difficulty in adapting to the home environment. Some behaviours are not abnormal but are difficult for owners to accept.

The most common behaviour problem in companion cats is that they sometimes urinate and defecate outside the litter box in the house. Organic causes include feline urologic syndrome (urinary bladder inflammation and calculi, or stones, in the urinary tract), blocked or impacted anal glands, and constipation. Emotional causes include the addition of a new family member—another cat, a child, or a spouse. Such changes may make the cat feel insecure, so that it deposits urine and feces around the house, possibly as territorial marks for security. Cats are creatures of habit, and any change in the family structure or in daily routines—resulting, for example, from a move or even from rearranging furniture—can be stressful.

Another common behaviour problem in cats is their natural desire to rake objects such as drapes and furniture with their claws. Surgical removal of the front claws to prevent property damage is normally repugnant to cat lovers. Cats can be trained to use carpeted scratching posts in the house to satisfy this behavioral need, which may be a combination of claw cleaning and sharpening and of territorial marking.

Many cats engage in social licking and in the grooming of their feline and human companions, which is a natural display of affection and dependence. Some also engage in nursing behaviour, sucking on people’s fingers and earlobes, on their own paws and tails, and on blankets and woolen clothing. Nursing may be a cat’s way of regressing and relaxing into kittenish behaviour. It is often more intense in cats weaned too early or in those malnourished in kittenhood. For various emotional reasons some cats may groom themselves to the point of self-mutilation or become compulsive wool suckers and eaters.

Pica—a hunger for nonnutritive substances—may be a symptom of the need for more roughage in the diet or of feline leukemia or other health problems. As with the dog, excessive eating and drinking is frequently associated with endocrine diseases such as diabetes and thyroiddysfunction. Cats often vomit soon after eating, which is most often caused by the accumulation of fur balls in the stomach, although a food allergy, feline leukemia, or other organic cause may be involved.

Active and healthy cats often race through the house as though they were crazed. These “evening crazies” (which can also erupt early in the morning) result from the cat’s ancient rhythm of actively hunting around dawn and dusk. In the domestic environment, this normal, instinctive behaviour often still occurs, to the consternation of some owners who fear that their cat may have rabies, a brain tumour, or an unstable personality.

Changes in animals’ behaviour should not, therefore, be dismissed as psychological (or as simple disobedience, as when a cat suddenly becomes unhousebroken, for example), since there may be an underlying physical cause. Nevertheless, abnormal behaviour in animals often does have a nonphysical, psychological, or emotional origin, which should always be considered in the diagnosis and treatment of the ailments of companion animals.

Other traits

The cat’s sleep patterns are different from those of dogs and humans. Dogs and humans have long periods of REM (rapid eye movement) sleep, the stage that is associated with dreaming. In contrast, the cat rarely lapses into REM sleep. Instead, it has a lighter, episodic sleep pattern that enables it to rest but to be instantly alert. When sick, cats have a tendency to withdraw and become inactive, which helps them conserve energy. A sick cat may seem lifeless but recover after a few days of withdrawal, which is one reason cats are said to have nine lives. (A sick cat should always be taken to a veterinarian, however; it is negligent simply to let nature take its course.)

Cats are known to have traveled hundreds of miles to find their owners in new homes to which they themselves have never been. Dogs have also performed such feats of so-called psi (psychic) trailing. Scientists have not been able to find a physiological or psychological explanation for this ability.

Cats As Pets

The popularity of the cat, especially of pedigreed breeds, has continued to grow. The cat’s independent personality, grace, cleanliness, and subtle displays of affection have wide appeal. Typically, cats are creatures of habit; they are inquisitive, but not adventurous, and are easily upset by sudden changes of routine. The ideal household cat has been separated from its mother between the ages of two and four months, raised in a clean home, kept away from unhealthy animals, and inoculated against common infectious cat diseases. Although cats often enjoy the company of other cats, especially when raised together from kittenhood, introducing a strange cat to other cats in the home can cause stress, aggression, and other behaviour problems. Cats are generally less sociable than dogs, who more readily accept a new pack member.

A good disposition and good health are important criteria for choosing a cat. Disposition varies only slightly between male and female cats. There are, however, distinct differences in disposition among the various pedigreed varieties; the Siamese, for example, is vocal and demanding, while the Persian is quiet and fastidious. The mixed breed, or “alley cat,” is a heterogeneous breed of unknown lineage; therefore, its disposition is difficult to assess. By chance, the mixed breed may prove a happier and healthier pet than a pedigreed one. On the other hand, the behaviour and vigour of the direct ancestors of pedigreed cats are indicative of the characteristics the offspring will possess as adults. But, as with the propagation of purebred dogs, the proliferation of pedigreed cats has resulted in an increase in inherited diseases, a major reason many people prefer mongrels or mixed breeds.

Nutrition

Cats should have a diet similar to that of their wild relatives. They are adapted by nature to be flesh eaters, as is shown by their alimentary tract and their dentition. The cat uses its canines to catch and kill prey, the molars to cut it up. Lack of flat-surfaced teeth prevents it from chewing or gnawing. The cat has a short intestine, and its stomach secretes digestive juices that act primarily on meat. Cats, however, like all meat-eating animals, ingest grass and other plants occasionally, and small quantities of vegetables may serve as both a laxative and a hair ball remover.

As cats are the strictest of all carnivorous mammals, they thrive on meat, but an all-meat diet is unbalanced and will lead to various nutritional deficiency diseases. Cats derive nutrients, including moisture, from their entire prey—hence the low thirst drive of most cats. Commercial dry pet foods, lacking moisture and overloaded with starches, are convenient for the owner but can contribute to many of the most common feline ailments—including obesity, urinary tract diseases, and diabetes mellitus. An obligate carnivore’s system is not equipped to handle a high dietary proportion of carbohydrates or to digest grain matter. It is therefore prudent to examine the ingredient list on commercial cat foods, including “prescription” foods, which often contain species-inappropriate ingredients that have no logical place in a cat’s diet. In addition, seafood is not recommended; many cats are allergic to it, and it may be contaminated with hazardous chemicals.

Getting as close to the natural carnivorous diet as possible by feeding a low-carbohydrate, meat-based diet can eliminate many of the most common ailments and diseases, which are not only painful for cats but also quite costly. Feline experts advise against ever feeding cats all-dry manufactured foods, because cats often grow to prefer those to the degree that they refuse other, healthier foods.

Reproduction

Cats reach reproductive age between 7 and 12 months. A breeding female (called a queen) can be in heat, or estrus, as many as five times a year. During these periods, which last about five days, the cat “calls,” or caterwauls, intermittently. The gestation period for cats averages 63 to 65 days, and birth usually lasts about two hours. The birth is often called kittening, and the kittens are called a litter. The average litter numbers four; however, the Abyssinian usually has fewer, the Siamese more.

Each kitten is born in a separate amniotic sac that is generally broken open at the moment of birth. If it is not, the mother breaks it. She also severs the umbilical cord and eats the placenta (which in many cases stimulates lactation). The kittens are born blind, deaf, and helpless, as are many other carnivores; their senses begin to function 10 or 12 days after birth. Soon after birth the mother licks her kittens; this action cleans them and helps stimulate their circulation. Kittens at birth lack distinctive colouring, and many do not acquire their characteristic markings and colour for weeks. For example, Siamese kittens are white at birth, while blue Persians have tabby markings and black Persians are brown.

Unlike wild cats that breed once a year, the domestic cat is capable of bearing up to three litters every year. Traditionally, regulation of the cat population was accomplished by the selective killing of the newborn. In modern times, however, sterilization—by means of relatively safe and simple operations known as spaying, neutering, or altering—has become common in affluent societies. Neutering is also viewed as an adaptive measure for indoor life.

Castration of the male, ideally around six or seven months of age, helps control the adult male’s tendency to “spray”—to mark objects in and around the house with his own urine. Spaying the female may help reduce the incidence of breast cancer in addition to eliminating uterine diseases and unwanted litters.
Neutered cats live longer than nonneutered ones, partly because they have less desire to roam. The average life expectancy for the cat is 10 to 15 years; the oldest cat on record attained the age of 38 years.

Diseases And Parasites

For many years cat treatments were simply extensions of those given dogs. Now, however, cat disorders of the skin, the eyes, the ears, the various systems (circulatory, respiratory, urinary, digestive, nervous, skeletal), and the blood, as well as contagious cat diseases and external and internal parasites, are studied, so that appropriate preventions and treatments can be developed.

Many cats die because their ailments become serious before their general conditions change sufficiently to reveal symptoms of illness. On the other hand, many symptoms used in diagnosing cat ailments are not definitive for given disorders. For example, signs of illness include general symptoms such as a dull coat, lack of appetite, and listlessness. Diarrhea may be a result of serious illness or simply reflect a change in diet. Tearing of the eyes, especially when accompanied by sneezing, may indicate conjunctivitis or a cold. Since, however, sneezing is the cat’s only mechanism for blowing its nose, not all sneezing indicates illness. Open sores, usually at the base of the ear, around the mouth, or on the toes, can point to an ear mite or a ringworm infection or to a fight with another animal.

Cats are attacked by several kinds of external and internal parasites. External parasites are most generally found in kittens, although they can occur in adults. The most frequent parasites are fleas, but lice, ticks, and ear mites also occur. Internal parasites include roundworms, tapeworms, and protozoan coccidia. Modern veterinary medicine has made all of these easy to control.

Panleucopenia, often called feline distemper, is the best-known viral disease in cats. Highly contagious, with a high mortality rate, it is seen most often in young cats. Vaccines are effective protective measures. Rabies is less of a problem with cats than with dogs, but all free-roaming cats should be vaccinated. Vaccines have also been developed for other feline diseases, including feline leukemia, pneumonitis (chlamydiosis), viral rhinotracheitis (cat influenza), and calicivirus infections.

Cats permitted to wander outdoors are exposed to a variety of hazards, including accidents, attacks from other animals, poisoning, fleas and other parasites, and contagious diseases such as feline acquired immune deficiency syndrome (AIDS). Cats that kill and eat rodents and other small animals can become infected with the parasitic protozoan Toxoplasma gondii, which can be transmitted to humans and causes the disease toxoplasmosis. Cats that share litter boxes with one another may increase their exposure to Tritrichomonas foetus, a single-celled flagellated protozoan that resembles Giardia. T. foetus infects the cat’s lower intestine, causing diarrhea, which may also contain mucus or fresh blood in some infected cats.

Genetics

Cats have never been bred for economic purposes; their matings are extremely difficult to control unless the animals are completely confined. There has been relatively little scientific breeding of cats, and the details of breed inheritance in these animals are not well known.

Cats are genetically far less plastic than dogs and therefore have not offered the same opportunities to breeders. The size differences between breeds in the domestic dog have no parallel in the domestic cat, nor has anything even remotely approaching the wide range of head shapes and body proportions in different breeds of dogs ever appeared among the cats. In cats the physical differences between one breed and another are largely differences in colour and texture of the coat.

Colour

The most common coat colours are blotched tabby, black, and orange. The latter term refers to the gene responsible for the expression of creams, yellows, gingers, and reds (“yellow” and “red” can also refer to this group of colours). Solid white is dominant to all other colours. Tortoiseshell, a piebald pattern that results from crossing a black, tabby, or other nonorange colour with a colour from the orange group, is a gender-linked trait. The orange gene is carried on the X chromosome; male tortoiseshells have one extra X chromosome, resulting in an abnormal XXY chromosomal pattern. Hence, male tortoiseshells are born only rarely and are usually sterile. Similarly, tortoiseshell-and-white cats (in North America often called calicoes) are almost always female.

Siamese dilution, the typical coloration of Siamese cats, has been described as a case of imperfect albinism and has been compared to the Himalayan pattern in rabbits, but its heredity is not well understood. There are also dilutions of the other ordinary colours: blue is dilute black and cream is dilute yellow. White spotting also occurs and is dominant to uniform colour.

Other characters

The long-haired coat of the Persian appears to be a simple unit character. It is recessive to short hair. Eye colour is known to be inherited, but its mode of inheritance is not thoroughly understood. Blue eye colour seems to be associated with dilution in coat colour; blue-eyed white cats are usually deaf, a fact commented on by Charles Darwin. Asymmetry of eye colour is inherited. Polydactylism, the presence of extra toes, is inherited and behaves as a dominant to the normal condition. It seems to be due to a single gene. The extra toes occur on the inner, or thumb, side of the foot.

Breeds

The number of recognized show breeds that have defined, inherited characteristics has increased dramatically since the late 1950s as cats have become more popular as home companions. The 30 to 40 distinctive breeds can be grouped into two general categories: the long-haired Persian and the domestic shorthair. Both of these breeds occur in various subcategories based on their coat colour, such as white, cream, chinchilla (or silver), smoke, tortoiseshell, and tabby (red, blue, and so on). Other distinctive and popular breeds include the Siamese (with seal point, blue point, chocolate point, and lilac point colour variations), the long-haired Himalayan, which resembles the Siamese in coloration, and the Abyssinian, Burmese, Manx, Rex, and Russian Blue.

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Jai Ganesh · 2019-05-10 00:30:40

339) Seal (Mammal)

Seal, any of 32 species of web-footed aquatic mammals that live chiefly in cold seas and whose body shape, round at the middle and tapered at the ends, is adapted to swift and graceful swimming. There are two types of seals: the earless, or true, seals (family Phocidae); and the eared seals (family Otariidae), which comprise the sea lions and fur seals. In addition to the presence of external ears, eared seals have longer flippers than do earless seals. Also, the fur of eared seals is more apparent, especially in sea lions.

Seals are carnivores, eating mainly fish, though some also consume squid, other mollusks, and crustaceans. Unlike other seals, the leopard seal (Hydrurga leptonyx) of the Antarctic feeds largely on penguins, seabirds, and other seals, in addition to fish and krill. The main predators of seals are killer whales, polar bears, leopard seals, large sharks, and human beings.

Seal Diversity

The Baikal seal (Phoca sibirica) of Lake Baikal in Siberia, Russia, is the smallest at 1.1–1.4 metres (3.6–4.6 feet) long and 50–130 kg (110–290 pounds), but some female fur seals weigh less. The largest is the male elephant seal (genus Mirounga leonina) of coastal California (including Baja California, Mexico) and South America, which can reach a length of 6.5 metres (21 feet) and a weight of 3,700 kg (8,150 pounds). The upper portions of seals’ limbs are within the body, but the long feet and digits remain, having evolved into flippers. Seals possess a thick layer of fat (blubber) below the skin, which provides insulation, acts as a food reserve, and contributes to buoyancy.

True seals of the genus Phoca are the most abundant in the Northern Hemisphere. They are fairly small, with little difference in size between the sexes. Ringed seals (P. hispida) have blotches over their entire bodies, harp seals (P. groenlandica) have a large blotch of black on otherwise mostly silver-gray fur, harbour seals (P. vitulina) have a marbled coat, and ribbon seals (P. fasciata) have dark fur with ribbons of paler fur around the neck, front limbs, and posterior part of their body.

Though especially abundant in polar seas, seals are found throughout the world, with some species favouring the open ocean and others inhabiting coastal waters or spending time on islands, shores, or ice floes. The coastal species are generally sedentary, but the oceangoing species make extended, regular migrations. All are excellent swimmers and divers—especially the Weddell seal(Leptonychotes weddellii) of the Antarctic. Various species are able to reach depths of 150–250 metres or more and can remain underwater for 20–30 minutes, with the Weddell seal diving for up to 73 minutes and up to 600 metres. Seals cannot swim as fast as dolphins or whales but are more agile in the water. When swimming, a true seal uses its forelimbs to maneuver in the water, propelling its body forward with side-to-side strokes of its hind limbs. Because the hind flippers cannot be moved forward, these seals propel themselves on land by wriggling on their bellies or pulling themselves forward with their front limbs. Eared seals, on the other hand, rely mainly on a rowing motion of their front flippers for propulsion. Because they are able to turn their hind flippers forward, they can use all four limbs when moving on land.

All seals must come ashore once a year to breed. Nearly all are gregarious, at least when breeding, with some assembling in enormous herds on beaches or floating ice. Most form pairs during the breeding season, but in some species, such as fur seals, the gray seal (Halichoerus grypus), and elephant seals, males (bulls) take possession of harems of cows and drive rival bulls away from their territory. Gestation periods average about 11 months, including a delayed implantation of the fertilized egg in many species. Cows are again impregnated soon after giving birth. Pups are born on the open ice or in a snow lair on the ice. The mother remains out of the water and does not feed while nursing the pups. The young gain weight rapidly, for the cow’s milk is up to about 50 percent fat.

Seals have been hunted for their meat, hides, oil, and fur. The pups of harp seals, for example, are born with white coats that are of value in the fur trade. The fur seals of the North Pacific Ocean and the ringed seals of the North Atlantic Ocean have also been hunted for their pelts. Elephant seals and monk seals were hunted for their blubber, which had various commercial uses. Seal hunting, or sealing, was so widespread and indiscriminate in the 19th century that many species might have become extinct if international regulations had not been enacted for their protection. The severe decline of sealing worldwide after World War II and the effects of international agreements aimed at conserving breeding stocks enabled several severely depleted species to replenish their numbers.

Harp seal, (Pagophilus, or Phoca, groenlandica), also called saddleback, medium-sized, grayish earless seal possessing a black harp-shaped or saddle-shaped marking on its back. Harp seals are found on or near icefloes from the Kara Sea of Russia west to the Gulf of St. Lawrence in Canada. The harp seal is both the best-known and among the most abundant of all seal species. Worldwide, the total population of harp seals is estimated at nearly 7.5 million animals, which are separated into three distinct populations. The largest population (approximately 5 million animals in 2000) inhabits the northwestern Atlantic and breeds both near the coast of Newfoundland and within the Gulf of St. Lawrence. The second largest population occurs in the vicinity of the Barents Sea, numbers between 1.5 million and 2 million animals, and breeds on the ice-covered White Sea in northwest Russia. The smallest population (approximately 300,000 animals) inhabits the area between Norway’s Jan Mayen Island and the eastern coast of Greenland, and its mating grounds are mainly located near Jan Mayen Island. Each population is considered by some authorities to be a separate subspecies.

Life Cycle

The colloquial names for harp seals vary by age and coloration. At birth, pups are known as “whitecoats” because of their pure white pelage. This stage lasts approximately two weeks. The subsequent growth of dark hair under their white fur produces a grayish coloration, and they are called “graycoats.” Once the white coat is completely shed, the seals become gray with dark spots and are often referred to as “beaters” because of the sound made by their tails as they learn to swim. At 13–14 months of age the seals molt again, and their spotted pelt remains. At this stage they are called “bedlamers.” The transition from bedlamer to adult coloration arrives with the onset of maturity, which usually occurs at four or five years of age.

Harp seals spend most of their lives in the water, though some have been known to ride bits of drifting sea ice for short distances during migration. All harp seals must come up on land or ice to give birth, rear their young, and molt. From late February to March, seals relocate to the southern limit of their range to breed and give birth.
Pups are born on the short-lived seasonal platform of pack ice. Each female gives birth to only one pup; twins are extremely rare. Pups weigh 11 kg (24 pounds) at birth, but they lack the thick layer of blubber present in adults. Instead, they are insulated by their thick fur and obtain energy from their mothers’ milk, which is rich in fat. During their 12-day nursing period, pups gain about 2 kg (4.4 pounds) per day of blubber, which allows them to attain a weight of approximately 36 kg (79 pounds) at weaning. Weaning is abrupt as females stop nursing their young in order to mate with males. During this time, since the pups do not feed for up to six weeks, they may lose over 50 percent of their body mass. Eventually, hunger motivates the pups to enter the water and start feeding on their own.

Average-sized adults of both sexes measure 1.8 metres in length (6 feet). Male harp seals typically weigh 135 kg (300 pounds), females weigh 120 kg (265 pounds), and the largest adults may reach 180 kg (400 pounds). The face of an adult harp seal is completely black, while the gray coloration of its body is accented by a black harp-shaped marking on its back. Adults typically hold this coloration between five years of age and the end of their lives. The maximum life span for the harp seal is 35 years.

Adult seals mate either within the water or on top of ice floes. When fertilization occurs, the egg develops into a blastocyst, which floats freely within the uterus for four months until it implants itself in the uterine lining for active development. This delay in implantation stretches gestation time to 11.5 months and effectively postpones the birth of young to the period when enough pack ice is available to act as a whelping platform.

Harp seals are not strong divers compared with other seal species. Their maximum dive depth is 370 metres (1,200 feet), and they may stay underwater for only 16 minutes before resurfacing. Though they consume a wide variety of prey, their diet is centred on small fishes such as capelin (Mallotus villosus), Arctic cod (Boreogadus saida), or polar cod (Arctogadus glacialis). They also eat numerous invertebrates. Contrary to popular belief, harp seals rarely consume the commercially important Atlantic cod (Gadus morhua). Polar bears (Ursus maritimus), killer whales (Orcinus orca), and large sharks are the natural predators of harp seals.

The Sealing Industry

Harp seals have been hunted commercially for over two centuries. The commercial sealing industry began with the harvest of adult harp seals in Newfoundland and Labrador during the middle of the 18th century. Recoverable seal parts include meat (for Asian pet food and meat markets), skins (for waterproof coats and boots), fur (for coats), genitals (for aphrodisiacs), and blubber (which is used to produce seal oil). In the 1960s, public indignation at the harvest of whitecoats brought strict regulations and tight governmental controls over harvesting activities, particularly with respect to humane killing and the enforcement of annual quotas. The Canadian hunt, occurring in the Gulf of St. Lawrence and off the coasts of Labrador and Newfoundland, was at the centre of this controversy, though the Norwegian and Russian hunts also received scrutiny. Since 1987 the harvesting of whitecoats has been illegal in Canadian waters; however, once the animals begin to shed their white fur when 12–14 days old, entering the graycoat stage, they may be hunted. Historically, the method of dispatch involved the use of a hakapik—a heavy wooden club with a small metal hook on one end—to crush the skull of the animal. Although legal and very efficient, this method has declined in use. It is far more common that seals are harvested with firearms. Most Canadian seal hunters are commercial fishermen who seek to supplement their incomes during the fishing off-season.

etween the 1950s and ’70s, hunting pressure caused the world harp seal population to decline to around 1.5 million animals. About this time the killing of whitecoats began to generate worldwide public outrage, and in 1983 the European Union instituted a ban on seal products. These factors brought about a collapse in the market. In response, during the 1980s and early ’90s Canada’s Department of Fisheries and Oceans (DFO) set the annual “total allowable catch” (TAC) of harp seals at 186,000 animals—though the average number of harp seals killed by Canadian hunters each year during this time actually dropped to about 51,000, possibly because of the negative publicity and loss of markets. The smaller hunts occurring during this time allowed the harp seal population to recover.

As an outgrowth of this recovery and the Canadian government’s successful marketing of seal fur in the economically emerging countries of East Asia, the DFO increased the TAC to 240,000 in 1996. For the remainder of the decade, an average of about 270,000 seals was killed each year. In the early part of the 21st century, the DFO introduced a series of measures to expand the harvest further. In 2003 the first three-year plan was adopted, designed to allow the harvesting of 975,000 seals over three years but to forbid the taking of more than 350,000 in any given year. The new plans have been forced to adapt to changing conditions, however. For instance, in 2007, because of reductions in ice coverage in the Gulf of St. Lawrence and the coasts of Labrador and Newfoundland, the TAC was reduced to 270,000. The annual seal harvest remains an object of highly publicized controversy, attracting much international media coverage.

Fur seal

Fur seal, any of several eared seals of the family Otariidae valued for the quality of their fur.

The northern fur seal (Callorhinus ursinus) is a migratory inhabitant of northern seas, breeding in summer on the Pribilof, Komandor (Commander), and other islands. Prized for its chestnut-coloured underfur, it is a gregarious, vocal animal that feeds on fish and other marine animals. The adult male is deep brown in colour with a grayish mane and grows to about 3.1 metres (10 feet) in length and 300 kg (660 pounds) in weight; the female is dark gray and grows to about 1.5 metres (5 feet) and 60 kg (130 pounds). In 1911, after more than a century of extensive slaughter, the northern fur seal was placed under protection. By the late 20th century there were thought to be some one million northern fur seals, but this number was declining. The overfishing of its prey and environmental fluctuations were believed to be partly responsible.

The eight species of southern fur seals (Arctocephalus) are distributed in the Southern Hemisphere, except for a herd of Guadalupe fur seals (A. townsendi) on Guadalupe Island off the northwest coast of Baja California. Southern fur seals are gray to brown or black in colour with chestnut-coloured underfur. Length averages about 1.2–1.8 metres (4–6 feet), but the South African, or Cape, fur seal (A. pusillus) and the Australian fur seal (A. pusillus doriferus) grow to lengths and weights of about 2.5 metres (8 feet) and 300 kg in the male, 1.8 metres and 120 kg (265 pounds) in the female. Like the northern form, southern fur seals are gregarious and carnivorous. By the late 1970s about 14,000 South American fur seals (A. australis) were being harvested annually. Other species, including the once-numerous New Zealand fur seal (A. forsteri), the Galapagos fur seal (A. galapagoensis), and the Juan Fernandez fur seal (A. philippii), all of which were hunted nearly to the point of extinction, have been protected by law.

Elephant seal

Elephant seal, also called sea elephant, either of the two largest pinnipeds (aquatic mammals of the suborder Pinnipedia): the northern elephant seal (species Mirounga angustirostris), now found mainly on coastal islands off California and Baja California; or the southern elephant seal (M. leonina), found throughout sub-Antarctic regions. Elephant seals are gregarious animals named for their size and for the male’s inflatable, trunklike snout. They are in the family Phocidae.

The northern elephant seal is yellowish or gray-brown, and the southern is blue-gray. The southern species has an extensive molting period in which considerable patches of hair and skin are shed. Males of both species attain a length of approximately 6.5 metres (21 feet) and a weight of about 3,530 kg (7,780 pounds) and are much larger than the females, which grow to 3.5 metres and weigh 900 kg. Elephant seals feed on fish and on squid or other cephalopods. The northern species is nonmigratory; the southern elephant seal, like the northern form, breeds and molts on land, but it winters at sea, possibly near the pack ice. During the breeding season, elephant seals become aggressive toward each other. The bulls fight to establish territories along beaches and to acquire harems of up to 40 cows. The cows produce single brownish black pups yearly. They mate about three weeks after delivery, and a three-month dormancy period ensues before the fertilized ovum implants. The total pregnancy lasts about 11 months. Both species have been hunted for their oil and in the 19th century were reduced almost to extinction; under protection, however, they have gradually increased in number and their survival is no longer threatened.

Harbour seal

Harbour seal, (Phoca vitulina), also called common seal, hair seal, or spotted seal, nonmigratory, earless seal (family Phocidae) found throughout the Northern Hemisphere. The harbour seal is whitish or grayish at birth and as an adult is generally gray with black spots. The adult male may attain a length and weight of about 1.8 m (6 feet) and 130 kg (290 pounds); the female is somewhat smaller. Found along coastlines and in a few freshwater lakes in Canada and Alaska, the harbour seal is a gregarious animal that feeds on fish, squid, and crustaceans. It is of little economic value and in some areas is considered a nuisance by fishermen.

Leopard seal

Leopard seal, also called Sea Leopard, (Hydrurga leptonyx), generally solitary, earless seal (family Phocidae) that inhabits Antarctic and sub-Antarctic regions. The only seal that feeds on penguins, young seals, and other warm-blooded prey, the leopard seal is a slender animal with a relatively long head and long, three-cusped cheek teeth. It is named for its black-spotted, gray coat, and it attains a maximum length and weight (greater in the female) of about 3.5 metres (12 feet) and 380 kilograms (840 pounds). The leopard seal has a reputation for ferocity but is not known to make unprovoked attacks on man; it is of no commercial importance.

Monk seal

Monk seal, any of three little-known tropical or subtropical seals of the genus Monachus, family Phocidae. Characterized by V-shaped hind flippers, monk seals are brown or black as pups, and dark gray or brown above, paler or whitish below as adults. They feed on fish, cephalopods, and crustaceans. Adults are 2–3 m (6.6–10 feet) long and weigh 225–275 kg (500–610 pounds).

Monk seals have been hunted extensively for fur, oil, and meat, and all three species are listed as endangered in the Red Data Book. The Caribbean, or West Indian, monk seal (M. tropicalis) was thought to be extinct by the early 1970s. The surviving species, both in danger of extinction, are the Mediterranean monk seal (M. monachus) and the Hawaiian, or Laysan, monk seal (M. schauinslandi). The seals are threatened by human disturbance of their coastal habitats, disease, and continued hunting. By the 1990s there were only about 1,400 Hawaiian monk seals and 300 to 600 Mediterranean monk seals still alive.

Ringed seal

Ringed seal, (Pusa, or Phoca, hispida), nonmigratory, earless seal (family Phocidae) of North Polar seas and a few freshwater lakes in Europe and on Baffin Island. Named for the characteristic pale rings on its grayish or yellowish coat, the ringed seal grows to about 1.5 m (5 feet) in length and 90 kg (200 pounds) in weight. It lives near the pack ice and feeds on crustaceans, mollusks, and some fish. The female bears a single white-coated pup each year in a den dug into the snow. A common species, the ringed seal is important to the Inuit (Eskimos) as a source of leather, oil, and meat.

Hooded seal

Hooded seal, (Cystophora cristata), also called bladdernose seal, large grayish seal with dark spots that is found in open waters of the North Atlantic and Arctic oceans. Hooded seals range from the Svalbard archipelago and the Barents Sea to the Gulf of St. Lawrence. Average-sized adult males measure about 2.6 metres (8.5 feet) long and typically weigh between 300 and 400 kg (660 and 880 pounds), whereas average-sized females measure 2.2 metres (7 feet) and weigh between 160 and 230 kg (350 and 500 pounds). Hooded seals are named for the nasal ornamentation occurring in mature males. Hanging like a wrinkled sac when relaxed, the appendage can be inflated to become a hood that covers the front of the face and the top of the head. Adult males also have an elastic nasal septum that can be inflated to become a reddish balloon in front of their face. These two unusual features have a role in attracting females and, when competing for females, advertising strength to other males.

Hooded seals are gregarious only during molting and breeding season. Breeding typically occurs between April and June, and pups are born on the pack ice during the following March and April. Pups weigh roughly 25 kg (55 pounds) at birth and already possess a thin layer of blubber. Their coloration is gray on the belly, with darker, almost bluish fur on their back. For this reason they are often referred to as “bluebacks.” Lactation lasts only four days, and pups drink 10 litres (2.6 gallons) of milk daily to gain 7 kg (15 pounds) per day during that period. Weaned pups weigh up to 60 kg (130 pounds). After weaning, pups fast for several weeks until hunger drives them to enter the water and start feeding on their own. Females reach maturity between three and six years of age, whereas males become sexually mature between five and seven years of age. Hooded seals may live for 25–30 years.

Hooded seals are strong swimmers that can dive to depths of over 1,000 metres (3,000 feet) and remain underwater for almost one hour. They feed on deepwater fishes—such as the Atlantic halibut(Hippoglossus hippoglossus), the Greenland halibut (Reinhardtius hippoglossoides), and redfish(Sebastes marinus)—and squid. Polar bears (Ursus maritimus), Greenland sharks (Somniosus microcephalus), and killer whales (Orcinus orca) are the natural predators of the hooded seal.

Valued for their pelts, meat, and oils, hooded seals are also hunted by humans. Hunting occurs most often in conjunction with efforts to harvest the more abundant harp seal. Trade in products made from hooded seals has been outlawed by the European Union since 1983; however, other countries (such as Canada) sanction limited harvesting by indigenous peoples and commercial interests. Worldwide, the population of hooded seals is estimated at 650,000 animals; however, there are concerns that forecasted decreases in Arctic ice extent due to global warming may substantially reduce their habitat and thus contribute to a population decline.

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Jai Ganesh · 2019-05-12 00:51:03

340) Llama

Llama, (Lama glama), South American member of the camel family, Camelidae (order Artiodactyla), closely related to the alpaca, guanaco, and vicuña, which are known collectively as lamoids. Unlike camels, lamoids do not have the characteristic camel humps; they are slender-bodied animals and have long legs and necks, short tails, small heads, and large, pointed ears. Gregarious animals, they graze on grass and other plants. When annoyed, they spit. Lamoids are able to interbreed and to produce fertile offspring.

Most herds of llamas are maintained by the Indians of Bolivia, Peru, Ecuador, Chile, and Argentina. The llama is primarily a pack animal but is also used as a source of food, wool, hides, tallow for candles, and dried dung for fuel. The largest of the lamoids, it averages 120 cm (47 inches) at the shoulder. A 113-kilogram (250-pound) llama can carry a load of 45–60 kg and average 25 to 30 km (15 to 20 miles) travel a day. The llama’s high thirst tolerance, endurance, and ability to subsist on a wide variety of forage makes it an important transport animal on the bleak Andean plateaus and mountains. The llama is a gentle animal, but, when overloaded or maltreated, it will lie down, hiss, spit and kick, and refuse to move. Llamas breed in the (Southern Hemispheric) late summer and fall, from November to May. The gestation period lasts about 11 months, and the female gives birth to one young. Although usually white, the llama may be solid black or brown, or it may be white with black or brown markings.

The llama and the alpaca (L. pacos) are domestic animals not known to exist in the wild state. They appear to have been bred from guanacos during or before the Inca Indian civilization to be used as beasts of burden.

Depending on the authority, the llama, alpaca, and guanaco may be classified as distinct species or as races of Lama glama. Because of certain structural features, the vicuña is sometimes classified into a separate genus from the other lamoids and is known as Vicugna vicugna.

Llamas are normally sheared every two years, each yielding about 3–3.5 kg of fibre. Llama fleece consists of the coarse guard hairs of the protective outer coat (about 20 percent) and the short, crimped (wavy) fibre of the insulating undercoat. The coarse fleece is inferior to the wool of the alpaca. The hair’s colour is usually variegated, generally in shades of brown, although there are some pure blacks and whites. Cleaning reduces the final yield of fleece to about 66–84 percent of the original weight. Individual locks of hair appear wavy; the fairly downy fibres have about two to four crimps per centimetre, but the coarse hairs are fairly straight. The hair’s length ranges from 8 to 25 cm, the coarse hairs being longest. The difference in diameter between the guard hairs and the downy fibre is not so great as it is in cashmere. Diameter ranges from about 10 to 150 micrometres (a micrometre is about 0.00004 inch) with undercoat fibre usually from 10 to 20 micrometres.

The scales of the outer layer of the fibre are indistinct, and the cortical layer contains pigment, with variations in the amount and distribution, which produces the various colours and tones. All but the finest fibres are likely to possess a hollow central core, or medulla, resulting in low density, which makes the fibre fairly light in weight.
Llama fibre is used, alone or in blends, for knitwear and for woven fabrics made into outerwear. It is used locally for rugs, rope, and fabric.

Llamas are members of the South American camelid family. They were domesticated from the Guanaco some 5000 years ago. Their ancestors inhabited the plains of North America and migrated south to the Andes about three million years ago!

Llamas can be grouped broadly into two types: Ccara and Tampuli.

“Ccara”, the most commonly seen type in the UK, has a short to medium length coat with very short fibre on the legs and head and tends to be larger than the Tampuli.

The“Tampuli" is more heavily woolled than the Ccara, its coat extending down the legs and often distinguished by a woolly "topknot".

The llama is the largest of the South American Camelids, weighing anything up to 400lbs (180kg) and standing approximately 4 ft (1.25m) at the shoulder.

Elegant with an exotic quality, llamas are strong, intelligent and hardy. They have a gentle temperament and inquisitive nature. With their distinctive "banana" shaped ears, they are found in a variety of colours from solid white to black and with varying shades and mixes of brown and grey.

Llamas are very diverse animals and are becoming much sought after in the UK for their many attributes

Their life span is generally 12 to 18 years although some may live to be over 20.

Field Pets: Llamas are becoming increasingly popular as field pets being gentle, quiet, hardy and undemanding. They live in harmony with other field stock and make good companions for lone ponies etc. They quickly learn to wear a halter and to be led. Llamas can be taught to pull a cart.

Trekking: Llamas can be walked for pleasure and will happily carry a pack, offering the long distance walker or the picnicking family both a fun companion and a willing helper!

A number of enterprises around the UK offer llama treks of varying lengths from just a half day upwards.

Fibre: llamas have a double fleece; an outer guard hair and a fine, soft undercoat much sought after by hand spinners. Llamas do not have to be sheared at all, but the undercoat can be used to make an array of wonderful garments and the guard hair can be used for other products such as bags, rugs etc. The fleece comes in many natural colours from white to black with a wide range of browns and greys in between.

Livestock guardians: Although gentle by nature, male llamas are protective of their group and are used very successful to keep predators from attacking lambs and even ducks and poultry.

Guanacos

The Guanaco is not domesticated in South America but there are a small number of domestic herds in the UK. The Guanaco has an outstanding fleece, even finer than the Llama. Guanacos are a honey shade of brown or cinnamon with white under-parts and dark grey head. They stand approximately 1 to 1.5 metres at the withers, weighing 100-150 Kgs.

Jai Ganesh · 2019-05-14 02:06:48

341) Cucumber

Cucumbers: Health Benefits & Nutrition Facts

Few foods are as cool as a cucumber. These low-calorie veggies contain many nutritional benefits, including hydrating properties and valuable nutrients.

There are hundreds of varieties of cucumber, and they come in dozens of colors, but the edible types are classified as being for either slicing or pickling, according to Cornell University's Growing Guide. Slicing cucumbers are cultivated to be eaten fresh, while pickling cucumbers are intended for the brine jar. Slicing cucumbers are usually larger and thicker-skinned than pickling ones.

In the United States, commonly planted varieties of slicing cucumber include Dasher, Conquistador, Slicemaster, Victory, Comet, Burpee Hybrid and Sprint, according to the World's Healthiest Foods website. Commonly planted varieties of pickling cucumber include Royal, Calypso, Pioneer, Bounty, Regal, Duke and Blitz.

While most people think of cucumbers as vegetables, they are actually a fruit. They contain seeds and grow from the ovaries of flowering plants. Cucumbers are members of the plant family Cucurbitaceae, which also includes squashes and melons. The most common type of slicing cucumber found in a grocery store is the garden cucumber, Cucumis sativus, according to World's Healthiest Foods.

Nutritional profile

Cucumbers are good sources of phytonutrients (plant chemicals that have protective or disease preventive properties) such flavonoids, lignans and triterpenes, which have antioxidant, anti-inflammatory and anti-cancer benefits, according to World's Healthiest Foods.

"We should definitely seek out foods that are nutrient-rich, using the positive approach of what to put on your plate vs. what to keep off," said Angela Lemond, a Plano, Texas-based registered dietitian nutritionist and spokesperson for the Academy of Nutrition and Dietetics. The peel and seeds are the most nutrient-dense parts of the cucumber. They contain fiber and beta-carotene. "Beta carotene is an antioxidant that helps with immunity, skin, eye and the prevention of cancer," said Lemond. A study published in the Pakistan Journal of Nutrition found that cucumber seeds were a good source of minerals, and contained calcium.

"Cucumbers are naturally low in calories, carbohydrates, sodium, fat and cholesterol," said Megan Ware, a registered dietitian nutritionist in Orlando, Florida. There are just 16 calories in a cup of cucumber with its peel (15 without). You will get about 4 percent of your daily potassium, 3 percent of your daily fiber and 4 percent of your daily vitamin C. They also "provide small amounts of vitamin K, vitamin C, magnesium, potassium, manganese and vitamin A," Ware said.

Here are the nutrition facts for cucumbers, according to the U.S. Food and Drug Administration, which regulates food labeling through the Nutritional Labeling and Education Act:

Health benefits of cucumbers

Hydration

Cucumbers are 95 percent water, according to Ware. This makes cucumbers a great way to stay hydrated, especially during the summer. A cup of cucumber slices is "nearly as thirst-quenching as a glass of water," according to Eating Well magazine.

"They say we can get 20-30 percent of our fluid needs through our diet alone, and foods like these certainly help," added Lemond. "Not only are they high in water content, they also contain important nutrients that play a part in hydration like magnesium and potassium."

The anti-inflammatory compounds in cucumbers help remove waste from the body and reduce skin irritation, according to the Cleveland Clinic. Preliminary research also suggests cucumbers promote anti-wrinkling and anti-aging activity, according to an article in the journal Filoterapia.

Cancer prevention

Cucumbers contain two phytonutrient compounds associated with anti-cancer benefits: lignans and cucurbitacins. In recent years, pharmaceutical companies have been paying special attention to cucurbitacins, hoping to use them in new cancer drugs. According to a 2010 research review published in Scientific World Journal, scientists have found that cucurbitacins can help block the signaling pathways that are important for cancer cell proliferation and survival.

Cucurbitacins can also inhibits the growth of pancreatic cancer cells, according to a 2009 study published in the Journal of Cancer Research looked at cucurbitacin B (which cucumber contains) on human pancreatic cancer cells and found that cucurbitacin supplements inhibited the growth of seven pancreatic cancer cell lines by 50 percent, and also increased apoptosis, of pancreatic cancer cells.

According to World's Healthiest Foods, lignans may protect against cancer through working with the bacteria in the digestive tract. The bacteria take the lignans and convert them into compounds such as enterodiol and enterolactone, which can bind onto estrogen receptors and possibly reduce the risk of estrogen-related cancers, such as ovarian, breast, endometrial and prostate cancers. The research is not yet clear on whether lignans actually assert anti-cancer benefits.

A 2009 meta-analysis published in the British Journal of Cancer found little or no association between lignan intake and reduced breast cancer risk. Similarly, most studies have not found significant correlations between lignan intake and reduced prostate cancer risk, according to the Linus Pauling Institute at Oregon State University, though one study of older Scottish men published in the British Journal of Nutrition showed that consuming an enterolactone-containing serum reduced the risk of prostate cancer.

On the other hand, a Journal of Nutrition study of nearly 800 American women found that those with those with the highest lignan intake had the lowest risk of ovarian cancer. Furthermore, a study published in the Journal of the National Cancer Institute looked at nearly 1,000 women in the San Francisco area and found that postmenopausal women with the highest lignan intakes had the lowest risk of endometrial cancer.

Skin

You've probably seen pictures of people at a spa relaxing with cucumber slices over their eyes. It turns out there's science behind this pampering ritual. Ware explained, "Cucumbers have a cooling and soothing effect that decreases swelling, irritation and inflammation when used topically. Cucumber slices can be placed on the eyes can decrease morning puffiness or alleviate and treat sunburn when placed on the affected areas." She also noted that high vegetable intake is associated with a healthy complexion in general.

Bone health

According to the University of Maryland Medical Center, in the past few decades, it has become clear that vitamin K is important to bone health, and one cup of cucumber contains about 19 percent of the recommended daily intake of vitamin K. One review published in Nutrition noted that vitamin K intake might reduce fracture rates, work with vitamin D to increase bone density and positively affect calcium balance.

The human body uses vitamin K when building bones, and the effects seem to be especially important for women. A large 2003 American Journal of Clinical Nutrition study showed that low vitamin K levels were associated with low bone density in women, but not in men. Another study published in the American Journal of Clinical Nutrition in 1999 found that low intakes of vitamin K were associated with an increased risk of hip fractures in middle-age women. This is especially interesting because the women saw results from eating lettuce, showing that dietary consumption of vitamin K via eating vegetables (not supplements) is beneficial. When it comes to men, the affects of vitamin K and bone health may become more apparent as they age: A 2000 study saw reduced risk of hip fracture among both elderly women and elderly men who consumed more vitamin K.

Antioxidants

"Foods that are high in antioxidants allow your body to function optimally. Antioxidants help prevent damage and cancer," Lemond said.

Cucumbers contain several antioxidants, including vitamin C, beta-carotene and manganese, as well as flavonoids, triterpenes and lignans that have anti-inflammatory properties. Vitamin C is well known for its immune system benefits, and beta-carotene has been shown to be beneficial for vision, according to the Mayo Clinic.

According to a 2010 animal study published in the Journal of Young Pharmacists, fresh extracts from cucumber showed increased scavenging of free radicals. Free radicals are associated with a variety of human diseases, but can sometimes be held in check by antioxidants, according to the Pharmacognosy Review.

Another study of cucumber extracts in animals, published in the Archives of Dermatological Research, found increased overall antioxidant benefits. Though this study focused on the cosmetic applications of this use of cucumbers, decreased free radicals can improve your inside organs as well as your skin.

An additional study published in Current Pharmaceutical Design found a positive association between the triterpene cucurbitacin and reduced inflammation, particularly in cancer cells. A review of triterpenes on the immune system, published in the Journal of Ethnopharmacology, suggested that they can help with inflammation and encouraged future research.

Heart health

"Eating a variety of fruits and vegetables of all kinds is associated with a reduced risk for many health conditions, such as heart disease, diabetes, stroke and obesity," said Ware. Cucumbers' potassium content may be especially helpful in this regard. One cup of sliced cukes contains only about 4 percent of the body's daily potassium needs, but it comes with significantly fewer calories than most high-potassium foods like bananas. Potassium is an essential part of heart health, according to the American Heart Association. A study of 12,000 adults, published in Archives of Internal Medicine, showed that those who consumed 4,069 mg of potassium each day lowered their risk of cardiovascular disease and ischemic heart disease by 37 percent and 49 percent, respectively, compared to those who took 1,793 mg per day.

Several studies have linked cucumber consumption to reducing hypertension. Many studies have linked it with lower blood pressure because it promotes vasodiliation (widening of the blood vessels), according to Today’s Dietitian. A 2017 study published in Public Health of Indonesia found that elderly participants with hypertension saw a significant decrease in blood pressure after consuming cucumber juice for 12 days. Additionally, a 2009 review in Indian Academy of Clinical Medicine suggested that hypertension sufferers incorporate cucumbers into their diets because of the fruit's low sodium content.

The vitamin K in cucumbers is also known to be essential in the blood-clotting process, according to the Harvard School of Public Health.

Digestion

A 2013 review in Fitoterapia noted that cucumbers might help relieve constipation because they provide both fiber and water. Tufts University notes that cucumbers can pack even more of a digestive punch if they are turned into pickles during a home-fermentation process. Cucumber pickles contain probiotic bacteria that promote healthy digestion and cultivating beneficial gut flora. Store-bought pickles usually do not have these bacteria because they have been boiled out.

Weight loss

Cucumbers are a low-calorie food therefore a popular ingredient in diet meals. A 2011 study in the journal Obesity found that greater water consumption correlated with more weight loss in middle-age and older adults. Participants who consumed 1 pint (500 milliliters) of water prior to eating a meal lost an average of 4 lbs. (2 kilograms) more than participants who did not. Snacking on water-dense foods like cucumbers can be an effective way to up water intake.

But Lemond cautions against relying too much on water-dense foods like cucumber. "We know that people that eat higher quantities of fruits and vegetables typically have healthier body weights. However, I do not recommend eating only cucumber. You will lose weight, but that weight will be mostly muscle," she said.

Brain health and memory

Recently, scientists have taken interest in the flavonoid fisetin. Cucumbers are a good source of fisetin, which studies have associated with protecting nerve cells, improving memory and decreasing the risk of Alzheimer's in mice, according to a 2013 review in the journal of Antioxidants & Redox Signaling. The same review found promising results for the relationship between fisetin and cancer prevention.

Risks of eating cucumbers

There can be a few risks from eating cukes. Pesticide consumption is one concern. Ware explained, "The Environmental Working Group produces a list each year of fruits and vegetables with the highest levels of pesticide residue, known as the Dirty Dozen. Cucumbers are one of the fruits and vegetables that the Environmental Working Group has placed on its Dirty Dozen list, meaning the exposure to pesticide residue is high."

Additionally, cucumbers may be waxed to help protect them during shipping. According to World's Healthiest Foods, both organic and conventionally grown cukes may be waxed, but organic ones can only use non-synthetic waxes with chemicals approved under organic regulations. For this reason and the pesticide concerns, World's Healthiest Foods encourages buying organic cucumbers. But Ware stipulated, "This does not mean you should avoid cucumbers altogether if you can't find or afford organic. The nutritional benefit of eating conventionally grown produce outweighs the risk of not eating produce at all."

Healthy as they are, you don't want to overdo it on cucumbers, said Lemond. "My recommendation is always to vary your selections. Cucumbers are great hydrating foods, so keep them in along with other plant foods that offer other benefits. Variety is always key."

Pickles

Pickling is a method of preserving food — and not only cucumbers — to prevent spoiling. There are two basic types of pickles: fermented and non-fermented, according to the World's Healthiest Foods.

Fermented pickles have been soaked in brine, which is water that has been saturated with salt. The word "pickle" comes from the Dutch word pekel, which means brine. Brines can also contain other ingredients, such as vinegar, dill seed, garlic and lime.

Dill pickles are brined with dill added to the solution, obviously. Kosher dills are brined with dill and garlic. "Kosher" in this case does not necessarily mean the cucumbers have been prepared according to kosher dietary laws, however; it just means garlic has been added to the brining process, according to the World's Healthiest Foods.
Gherkin pickles are usually just immature cucumbers, according to Cornell University.

Jai Ganesh · 2019-05-16 01:07:13

342) Bat (Mammal)

5 Surprising Facts About Bats

5. There Are More Than 1,200 Species of Bats.

Bats are usually divided into two suborders: Megachiroptera (large Old World fruit bats) and Microchiroptera (small bats found worldwide). They range in size from the giant flying foxes, with wingspans up to 5 feet (1.5 meters), to the itty-bitty bumblebee bat, with only a 6-inch (15-cm) wingspan. There are even three different species of blood-drinking vampire bats.

4. Bats Are the Only Mammals Capable of Flight.

Like all true mammals, baby bats are nourished with milk from their mothers. Bats bear live young—usually only one, although some species can have up to three or four at a time. But no other mammal can fly like a bat can. “Flying” squirrels and similar mammals can only glide at best. In order to make flight possible, bats digest their food extremely fast, sometimes excreting within 30 to 60 minutes of eating. That helps them keep their weight down.

3. Bat Droppings Can Be Used to Make Gunpowder.

Speaking of bat droppings, also known as guano, they are high in potassium nitrate (saltpeter) and are often used as fertilizer. The saltpeter can also be extracted for use in gunpowder and explosives, and bat guano was an important resource for that purpose during the American Civil War. Bat guano has also been found to preserve fossils.

2. Not All Bats Hang Upside Down.

Almost all bat species hang upside down. Their feet have evolved to be relaxed in a clenched position (difficult for a human to imagine). When they’re ready to fly, they let go and gain momentum from falling, since their little legs and wings can’t give them the kind of lift birds get. However, there are six species of bats that don’t hang upside down. Most of these bats have suctioning pads on their limbs that let them stick to leaves or other surfaces.

1. Bats Aren’t Really Blind.

Only the smaller species of bats use echolocation as their main means of orienting themselves. Bigger bats can see better than humans. Sight is a blessing and a curse, however, because sight can override echolocation signals. For instance, a bat may fly into a window because it sees light outside, even if echolocation tells it the surface is solid.

Bat, (order Chiroptera), any member of the only group of mammals capable of flight. This ability, coupled with the ability to navigate at night by using a system of acoustic orientation (echolocation), has made the bats a highly diverse and populous order. More than 1,200 species are currently recognized, and many are enormously abundant. Observers have concluded, for example, that some 100 million female Mexican free-tailed bats (Tadarida brasiliensis mexicana) form summer nursery colonies in Texas, where they produce about 100 million young in five large caves. The adult males are equal in number to the females, though they do not all range as far north as Texas. Furthermore, this species is found throughout tropical America. Thus, one species alone numbers, at the very least, in the hundreds of millions.

General Features

All bats have a generally similar appearance in flight, dominated by the expanse of the wings, but they vary considerably in size. The order is usually divided into two well-defined suborders: the Megachiroptera (the large Old World fruit bats) and the Microchiroptera (small bats found worldwide). Among members of the Megachiroptera, flying foxes(Pteropus) have a wingspan of 1.5 metres (about 5 feet) and a weight of 1 kg (2.2 pounds). The largest insectivorous bat is probably the hairless, bat (Cheiromeles torquatus); it weighs about 250 grams (about 9 ounces). The largest of the carnivorous bats (and the largest bat in the New World) is the spectral bat (Vampyrum spectrum), also known as the tropical American false vampire bat, with a wingspan of over 60 cm (24 inches). The tiny hog-nosed, or bumblebee, bat (Craseonycteris thonglongyai) of Thailand is one of the smallest mammals. It has a wingspan of barely 15 cm (6 inches) and weighs about 2 grams (about 0.07 ounce).

Bats vary in colour and in fur texture. Facial appearance, dominated by the muzzle and ears, varies strikingly between families and often between genera. In several families a complex fleshy adornment called the nose leaf surrounds the nostrils. Although the exact function of these facial appurtenances has yet to be determined, scientists believe they may help to direct outgoing echolocation calls. Wing proportions are modified according to mode of flight. The tail and the membrane between the legs also differ, perhaps as adaptations to feeding, flight, and roosting habits. Finally, bats vary in the postures they assume when roosting, particularly in whether they hang suspended or cling to a wall and in the manner in which the wings are folded and used.

Distribution

Bats are particularly abundant in the tropics. In West Africa, for example, more than 30 genera embracing nearly 100 species have been cataloged; in the United States 19 genera, totaling about 45 species, are known. Of the 18 bat families, 3—the vesper bats (family Vespertilionidae), free-tailed bats (family Molossidae), and horseshoe bats (family Rhinolophidae)—are well represented in the temperate zones. A few American leaf-nosed bats (family Phyllostomidae) range into mild temperate regions. Several vesper bats range well into Canada.

The Vespertilionidae are found worldwide except in the polar regions and on isolated islands. The brown bats of genus Myotis have a range almost equal to that of the entire order. The free-tailed bats and sheath-tailed bats (family Emballonuridae) also encircle the Earth but are restricted to the tropics and subtropics. The horseshoe bats extend throughout the Old World, the roundleaf bats (family Hipposideridae) and Old World fruit bats (family Pteropodidae) throughout the Old World tropics, and the leaf-nosed bats throughout the New World tropics and slightly beyond. The other families have more restricted ranges.

Importance to humans

Most bats are insectivorous, and they are important to humans primarily for their predation on insects, for pollination, and for seed dispersal. Little is known of the spectrum of insect species consumed, but the sheer quantity is formidable. The Mexican free-tailed bats of Texas have been estimated to consume about 9,100 metric tons (10,000 tons) of insects per year. Bats would thus seem to be important in the balance of insect populations and possibly in the control of insect pests.

Some bats feed on pollen and nectar and are the principal or exclusivepollinators of a number of tropical and subtropical plants. Others feed on fruit and aid in dispersing seeds, although bananas and figs must in some cases be protected from fruit-eating bats by early harvest or by nets.

Vampire bats (family Phyllostomidae, subfamily Desmodontinae) are considered serious pests of livestock in some parts of tropical America because the small wounds they cause provide egg-laying sites for parasites and because the vampires may transmit rabies and trypanosomiasis to cattle. Other bats also carry rabies or related viruses.

The guano (droppings) of insectivorous bats is still used for agricultural fertilizer in many countries and in the past was used as a source of nitrogen and phosphorus for munitions. Large guano deposits, in addition, cover and thus preserve many archaeologically interesting artifacts and fossils in caves.

In tropical regions large colonies of bats often inhabit houses and public buildings, where they attract attention because of their noisiness, guano, and collective odour. In western culture bats have been the subject of unfavourable myths; in parts of the Orient, however, these animals serve as symbols of good luck, long life, and happiness. In some parts of Southeast Asia and on some Pacific islands, flying foxes (Pteropus) are hunted for food. Small bats are also widely but irregularly eaten.

Certain physiological aspects of some bats, particularly those involving adaptations for long hibernation, daily lethargy, complex temperature regulation, acoustical orientation, and long-distance migrations, are of interest to biologists.

In species and numbers, bats constitute an important and generally nonintrusive form of wildlife. Several zoos have established interesting exhibits of bats; indeed, some flying foxes and fruit bats have been exhibited in European zoos since the mid-19th century, and they have been kept widely for research purposes. Bats are interesting pets but require specialized care.

Natural History

Behaviour

Activity patterns

Nocturnal activity is a major feature of the behavioral pattern of bats: nearly all species roost during the day and forage at night. Carnivorous bats, vampire bats, and perhaps fishing bats (see bulldog bat) may have an advantage at night over inactive or sleeping prey. In addition, nocturnal flight protects bats from visual predators, exposure to the sun, high ambient temperature, and low relative humidity. The large area of wing skin without cover might mean that bats would absorb rather than radiate heat if they were active during the day. They would also lose body water required for temperature regulation and would then be forced to forage near water or somehow retain more water (and thus more weight) in their bodies during flight.

The nocturnal activity pattern in bats is probably kept in synchrony with changing day lengths by their exposure to light at dusk or dawn. Bats often awaken and fly from the cave exit well before nightfall. Should they be too early, their internal clock may be reset. A few species of bats, including a flying fox (Pteropus samoensis), the yellow-winged bat (Lavia frons), and the greater sac-winged bat Saccopteryx bilineata, may forage actively during the day, but little is yet known of their special adaptations.

Locomotion

Flight is the primary mode of locomotion in all bats, although the flight styles vary. Some groups (the free-tailed bats, for example) are adapted for flight in open spaces and high altitudes. They have long, narrow wings, swift flight, and a large turning radius. Slit-faced bats (Nycteridae), false vampire bats (Megadermatidae), and others are adapted for hovering as they pick prey off vegetation or feed on flowers. These bats have short, broad wings, slow flight, and a small turning radius. Some bats take flight easily from the ground: members of the genus Macrotusdo so simply by flapping, while vampire bats (Desmodus) leap into the air and then spread their wings and fly. The free-tails, however, roost well above the ground because, upon takeoff, they fall before becoming airborne.

Though flight speeds in the wild are hard to measure, four vesper bat species, carefully observed, have been timed on average at 18.7 to 33.3 km (11.7 to 20.8 miles) per hour. In flight the posture of each of the four fingers incorporated into the wing is under precise and individual control. Finger and arm postures, which determine the shape, extension, and angle of the wings, govern such actions as turning, diving, landing, and hovering. Except when interrupted by insect catches or obstacles, bat flight paths are straight. Insects may be pursued and captured at a rate of up to two per second; during each catch the flight path is interrupted and thus appears erratic.

In many cases there is little locomotion other than flight. Bats that hang in caves may move across the ceiling by shifting their toehold, one foot at a time. A few genera, especially among the Old World fruit bats (family Pteropodidae), may crawl along branches in a slothlike posture, using their thumb claws as well as their feet. The sheath-tailed bats (family Emballonuridae) and mouse-tailed bats (family Rhinopomatidae) hang on vertical surfaces suspended by their hind claws but with their thumbs and wrists propped against the surface. In this orientation they can scramble rapidly up or down and forward or backward, as well as sideways.

Bats of many families walk or crawl on either horizontal or vertical surfaces, using hind feet, wrists, and thumbs. Many move freely either backward or forward, a convenience for entering and leaving crevices. The vampire bats may also leap from roost to roost. The disk-winged bats (family Thyropteridae) and sucker-footed bat (one species, family Myzopodidae), as well as the bamboo bats (Tylonycteris), have specialized wrist and sole pads for moving along and roosting on the smooth surface of leaves or bamboo stalks. Bats are not known to swim in nature except, perhaps, by accident. When they do fall into water, however, they generally swim competently.

Roosting

Bats choose a variety of diurnal roosts, although the roost requirements of many bats, which are rather precise in terms of light, temperature, and humidity, limit their distribution. Each species favours a particular kind of roost, though this varies with gender, season, and reproductive activity. Many bats prefer isolated or secure roosts—caves, crevices in cliff faces, the interstices of boulder heaps, tree hollows, animal burrows, culverts, abandoned buildings, portions of buildings inaccessible to humans or infrequently accessed by them (i.e., a roof, attic, or hollow wall), or the hollow core of bamboo stalks. Some species roost externally—on tree trunks or in the branches of trees, under palm leaves, in unopened tubular leaves, or on the surface of rocks or buildings. For some the darkness, stability of temperature and humidity, and isolation from predators provided by caves and crevices seem essential. Others prefer the heat and dryness of sun-exposed roosts. Many bats also occupy nocturnal roosts, often rocky overhangs or cave entrances, for napping, for chewing food, or for shelter from bad weather. Many species likewise choose special nursery or hibernation roosts. Buildings are so widely exploited by bats (especially vesper bats, free-tailed bats, and sheath-tailed bats) that many species have probably become more abundant since the advent of architecture.

Bats are usually colonial; indeed, some form very large cave colonies. Generally, large colonies are formed by bats that roost in dense clusters, pressing against one another, although many are widely spaced and do not touch when roosting. Some of the Old World fruit bats strikingly defoliate the trees on which they roost. In trees flying foxes (Pteropus) may form outdoor camps numbering hundreds of thousands of individuals. Many species form smaller groups of several dozen to several hundred. Less commonly, bats are solitary; sometimes the adult female roosts only with its most recent offspring. Occasionally, one gender is colonial and the other is apparently solitary. The advantages of colonial or solitary life and the factors that govern colony size in bats with colonial predilection have not yet been established.

Elaborate communities of other animals are often satellites of cave-bat colonies. Among these are cave crickets, roaches, blood-sucking bugs, a variety of parasites (e.g., fleas, lice, ticks, mites, and certain flies), and dermestid beetles and other insects that feed on cave-floor debris—guano, bat and insect corpses, and discarded pieces of food or seeds. Molds and other fungi are also conspicuous members of the cave-floor community. Bats and their excretions alter the cave environment by producing heat, carbon dioxide, and ammonia.

Migration

Many bats of temperate climates migrate annually to and from summer roosts and winter hibernation sites, with an individual often occupying the same roosts in seasonal sequence each year. Members of the same species may converge on a single hibernation cave or nursery roost from many directions, which indicates that the choice of migration direction to and from these caves cannot be genetically determined. When migration occurs, however, is probably genetically determined (i.e., instinctive) and influenced also by weather conditions and the availability of food. Nothing is known of how bats recognize migration goals or how succeeding generations learn their locations. Female young born at a nursery roost may memorize its location, but how they know where to go at other times is not clear. Likewise, little is yet known of energy storage, navigation, or other specializations for migrations.

Female Mexican free-tailed bats migrate from central Mexico to Texas and adjacent states each spring, returning south in the fall. Mating probably occurs in transient roosts during the spring flight. The migration is believed to remove pregnant and lactating females to a region of high food supply where they need not compete with males of their own species. Presumably they return to Mexico for its suitable winter climate and food supply and to meet their mates.
The North American red and hoary bats (Lasiurus borealis and L. cinereus) and the silver-haired bat (Lasionycteris noctivagans) migrate in the fall from the northern United States and Canada to the southern United States and beyond, returning in the spring.

Orientation

Bats of the suborder Microchiroptera orient acoustically by echolocation(“sonar”). They emit short high-frequency pulses of sound (usually well above the range of human hearing) and listen to the echoes returning from objects in the vicinity. By interpreting returning echoes, bats may identify the direction, distance, velocity, and some aspects of the size or nature (or both) of objects that draw their attention. Echolocation is used to locate and track flying and terrestrial prey, to avoid obstacles, and possibly to regulate altitude; orientation pulses may also serve as communication signals between bats of the same species. Rousette bats(megachiropteran genus Rousettus) have independently evolved a parallel echolocation system for obstacle avoidance alone. Echolocation pulses are produced by vibrating membranes in the larynx and emitted via the nose or the mouth, depending upon species. Nose leaves in some species may serve to channel the sound.

The echolocation signals spread in three dimensions on emission, the bulk of the energy in the hemisphere in front of the bat or in a cone-shaped region from the nostrils or mouth. When the sound impinges on an intervening surface (an insect or a leaf, for example), some of the energy in the signal is reflected or scattered, some absorbed, and some transmitted and reradiated on the far side of the surface; the proportion of sound energy in each category is a function of wavelength and of the dimensions, characteristics, and orientation of the object. The reflected sound spreads in three dimensions, and some portion of it may impinge on the bat’s ears at perceptible energy levels.

Bats’ external ears are generally large, which probably enhances their value for detecting the direction of incoming signals, and their middle and inner ears are specialized for high-frequency sensitivity. In addition, the bony otic (auditory) complex is often isolated acoustically from the skull, which probably improves signal comparison by both ears. The thresholds and ranges of hearing in several genera of bats have been studied, and in each case the region of maximum sensitivity has been found to coincide with the prominent frequencies of the outgoing echolocation signals.

The characteristics of echolocation pulses vary with family and even with species. Echolocation pulses of a substantial number of bat species have been analyzed in terms of frequency, frequency pattern, duration, repetition rate, intensity, and direction. The prominent frequency or frequencies range from 12 kilohertz (1 kilohertz is equivalent to 1,000 hertz, or cycles per second) to about 150 kilohertz or more. Factors influencing frequency may include bat size, prey size, the energetics of sound production, inefficiency of the propagation of high frequencies, and ambient noise levels.

Orientation pulses may be of several types. The individual pulse may include a frequency drop from beginning to end (frequency modulation[FM]), or the frequency may be constant (CF) during part of the pulse, followed by a brief FM sweep; either FM or CF pulses may have high harmonic content. The pulse duration varies with the species and the situation. During cruising flight the pulses of the greater false vampire bat (Megaderma lyra) are 1.5 milliseconds (0.0015 second), those of Wagner’s mustached bat (Pteronotus personatus) 4 milliseconds, and those of the greater horseshoe bat (Rhinolophus ferrumequinum) 55–65 milliseconds. In goal-oriented flight, such as the pursuit of an insect or the evaluation of an obstacle or a landing perch, the pulse duration is systematically altered (usually shortened) with target distance, sometimes ending with pulses as short as 0.25 millisecond.

During insect pursuit, obstacle avoidance, and landing maneuvers, there are three phases of pulse output design: search, approach, and terminal. The search phase, during which many bats emit about 10 pulses per second, precedes specific attention to a target. In the approach phase, which starts when the bat detects an object to which it subsequently devotes its attention, the bat raises the pulse rate to about 25 to 50 per second, shortens the pulses with decreasing distance, and often alters the frequency pattern. The terminal phase, which often lasts about 100 milliseconds, is characterized by extremely short pulses, repeated as rapidly as 200 or more times per second, and ceases as the bat intercepts the target or passes it (the stimulus being, perhaps, the cessation of echoes); another search phase follows. During the brief terminal phase (a fraction of a second), the bat is engaged in final interception (or avoidance) maneuvers and appears to pay little attention to other objects.
In addition to sensitive ears, the use of echolocation to gain sensory information requires integration of the vocal and auditory centres of the brain. Not only must the nervous system of the bat analyze in a few thousandths of a second the reflected, and thus altered, form of its own pulse, but it must separate this echo from those of other individuals and from others of its own pulses. All of this must be done while the animal (and often the target) is moving in space. In the laboratory, bats have been found to be able to identify, pursue, and capture as many as two fruit flies (Drosophila, about 3 mm [0.12 inch] long) per second and to locate and avoid wires as fine as 0.1 or even 0.08 mm (0.004 or 0.003 inch) in diameter.

Research has provided some information on the mechanisms of bat sonar. There is evidence that the multiple frequencies of FM or harmonic patterns serve in determining target direction. The relative intensities of the various frequencies are different at each ear, which allows the animal to determine the target’s direction when three or more frequencies are received. Target velocity may be measured by CF bats through the use of the Doppler shift, a change in perceived frequency due to the relative motion of the bat and its target. Changes in pulse-echo timing may provide information on target distance and velocity. The ratio of useful signal to background noise is increased by several mechanisms, including specializations of the middle ear and its ossicles (tiny bones), isolation of the cochlea (the area where sound energy is converted into nerve impulses), and adaptations of the central nervous system.

Food habits

Most bats feed on flying insects. In some cases prey species have been identified from stomach contents or from discarded pieces under night roosts, but such studies have not yet provided an adequate measure of the spectrum of bat diets. Bats identify and track insects in flight by echolocation. Large insects may be intercepted with the wing membranes and pulled into the mouth. Some bats feed on arthropods, such as large insects, spiders, and scorpions, that they find on the ground, on walls, or on vegetation. These bats may either land on and kill their prey before taking off with it or pick it up with their teeth while hovering.
Two genera (Noctilio and Myotis) include at least one species that catches small fish and possibly crustaceans. All fish-eating species also feed on flying insects or have close relatives that do so. Each is specialized in having exceptionally large hind feet armed with long, strong claws with which the fish are gaffed.

The Megachiroptera and many of the phyllostomid genera feed on a variety of fruits, often green or brown in colour; usually such fruits are either borne directly on wood or hang well away from the bulk of the tree and have a sour or musky odour.

The Old World fruit bat subfamily Macroglossinae (and some other fruit bats) and certain leaf-nosed bats feed, at least in part, on nectar and pollen. Many tropical flowers, adapted for pollination by these bats, open at night, are white or inconspicuous, have a sour, rancid, or mammalian odour, and are borne on wood, on pendulous branches, or beyond or above the bulk of the plant. The phyllostomid Glossophaginae may also feed on flowers. (See Sidebar: Bat-Loving Flowers.)
Several phyllostomid and megadermatid genera are carnivorous, feeding on small rodents, shrews, bats, sleeping birds, tree frogs, and lizards. The true vampires, which feed on the blood of large mammals or birds, land near a quiet prospective victim, walk or jump to a vulnerable spot on it where the skin is relatively exposed—the edge of the ear or nostril, around the math, or between the toes, for example—make a scooping, superficial bite from which the blood oozes freely, and lap the blood with very specialized tongue movements. Each vampire requires about 15 millilitres (about half an ounce) of blood per night.

The interaction of bats with their food, be it insects, fruit, or flowers, probably has a substantial impact on some biological communities. Many plants are dependent on bats for pollination; other plants benefit from seed dispersal by bats. Moths of two families are known to take evasive or protective action on hearing bat pulses nearby, an adaptationthat implies heavy predation.

Maintenance behaviour

Bats are meticulous in their grooming, spending a fair part of the day and night combing and grooming their fur and cleansing their wing membranes. Generally, they comb with the claws of one foot while hanging by the other; they remove the combings and moisten their claws with their lips and tongue. On the wing membranes in particular, they use the mouth meticulously, perhaps oiling the skin with the secretions of dermal (skin) glands while cleansing it.

Social interactions

Although social interactions per se have not been observed between adult bats, they are known to often segregate by gender. As noted above, pregnant females in many species occupy special nursery roosts until their young are independent. In some species the sexes occupy the same general roost but gather in separate clusters. In others the sexes intermingle or arrange themselves into a pattern within a group—the females centrally, for example, and the males peripherally. Sexual segregation during foraging has been reported for several species. Among bats that migrate over long distances, such as Mexican free-tailed, red, and hoary bats, the sexes may meet only briefly each year.

Life cycle

Details of the life cycle are known for only a few species. In northern temperate zone species, there is an annual cycle of mating activity, with birth taking place between May and July. In males the testes, normally located in the abdominal region, descend seasonally into the scrotum, and active spermatogenesis occurs. In females sexual receptivity may be associated with egg maturation and release. Tropical bats may exhibit a single annual mating cycle or may be diestrous (i.e., have two periods of fertility) or polyestrous (have many).

The mating cycles of entire populations are closely synchronized, so almost all mating occurs within a few weeks. The periods of gestation, birth, lactation, and weaning are also usually synchronized. Gestation varies in duration: five or six months in flying foxes (Pteropus), more than five months in vampire bats (Desmodus), three months in some small leaf-nosed bats (Hipposideros), and 6 or 7 to 14 weeks in several small vesper bats (family Vespertilionidae). The length of gestation may be influenced by both ambient (surrounding) and body temperature.

In several North American and northern Eurasian vesper and horseshoe bats that hibernate, copulation occurs in the fall, and the sperm are stored in the female genital tract until spring. Ovulation, fertilization, and implantation occur after emergence from hibernation, when the female again has available an abundant food supply and a warm roost. Such favourable environmental conditions greatly enhance the young bat’s chances of survival.

Most bats bear one young, but the big brown bat (Eptesicus fuscus) may bear twins, and the Eastern red bat (Lasiurus borealis) bears litters of one to four.
At birth the young, which may weigh from one-sixth to one-third as much as the mother, usually have well-developed hind legs with which they hold on to their mother or to the roost. Their wings are very immature. The young are hairless or lightly furred and are often briefly blind and deaf. The infants are nourished by milk for a period of about five or six weeks in many small bats and for five months in the Indian flying fox (Pteropus giganteus). By two months of age, most smaller bats have been flying and foraging for three or four weeks and have achieved adult size.

In many species females late in pregnancy migrate to special nursery roosts, in which large numbers of pregnant females may aggregate, usually to the exclusion of nonpregnant females, males, and bats of other species. In some cases the nursery roosts seem to be chosen for their high temperature, which may derive from the sun, from the bats themselves, or from decomposing guano. When foraging, some bats (Erophylla) leave their infants hanging quietly, one by one, on the cave wall or ceiling. In the case of the Mexican free-tailed bat and a few others, the closely spaced infants may move about and mingle on the wall. Some bats carry their young with them for a short period of time. Generally, each mother, on returning to her roost, seeks out her own offspring by position, smell, and acoustical exchange.
Some bats achieve sexual maturity in their first year, others in their second. Infant mortality appears to be high. Developmental and genetic errors and disease take their toll, but accidents seem to cause more serious losses—the young may fall from the ceiling or perhaps have serious collisions in early flight attempts. A fair number of bats probably fail to make the transition from dependent infants to self-sufficient foragers.

Adult bats, on the other hand, have low mortality. Predation is rarely serious, especially for cave-dwelling species. Disease, parasitic infestation, starvation, and accidents apparently take small tolls. There are records of several big brown (Eptesicus fuscus), little brown (Myotis lucifugus), and greater horseshoe bats (Rhinolophus ferrumequinum) that have lived more than 20 years, and a few have lived more than 30. Probably many bats in temperate climates live more than 10 years. Longevity has not been established for most tropical species, but a few are known to live for more than 10 years.

Several factors probably contribute to the unusual longevity of bats. Generally isolated roosts and nocturnal flight substantially protect them from predation, from some elements of weather, and from exposure to the sun. Their largely colonial way of life may ensure that entire populations experience contagious infection and subsequent immunity; indeed, such a pattern in the past may have hastened adaptation to disease. The persistent use of various seasonal roosts probably ensures isolation and security, food and water supplies, and access to mates. Many bats, moreover, reduce their body temperature at rest. Not only is there a probability that this conserves some cellular “machinery,” since metabolism is reduced, but fewer hours need to be spent in actively seeking food and water.

Form And Function

Anatomical specializations

Bats are mammals with front limbs modified for flight. The chest and shoulders are large and well-muscled to provide power to the wings. The hips and legs are slender, as they do not usually support any body weight. Wing shape, governed by the relative lengths of the forearm and the fingers, varies greatly, in adaptation to flight characteristics. The fingers, other than the thumb, are greatly elongated and are joined by a membrane that extends from the posterior border of the forearm and upper arm to the side of the body and leg as far as the ankle or foot. The wing membrane consists of two layers of skin, generally darkly pigmented and hairless, between which course blood vessels and nerves. When not fully extended, the wing skin is gathered into wrinkled folds by elastic connective tissue and muscle fibres. Some of the fingers, especially the third, fold over when the bat is not in flight; the wing may then be quite tightly folded or may partly enfold the bat’s undersurface. The thumb, always free of the wing membrane, is used for walking or climbing in some species; in others it is used for handling food. Only the thumb—and occasionally the index finger—ends with a claw. Bats that walk often have pads or suction disks on their thumbs or wrists or both, and many female bats use their thumbs to suspend themselves, hammock fashion, when giving birth.

Most bats have a membrane, consisting of skin like that of the wings, that extends between their legs (the uropatagium, or interfemoral membrane). In the midline the interfemoral membrane is usually supported, at least in part, by the tail, with the distal edges often shaped in flight by greatly elongated heel bones, or calcars. The interfemoral membrane, especially well-developed in insectivorous, carnivorous, and fish-eating bats, is less-well-developed or even absent in the vampires and in fruit- and flower-feeding bats. Many bats, on catching large prey in flight, bring the membrane forward and, by flexing the neck and back, tuck the prey against and into the membrane. With this maneuver the bat takes hold of the victim headfirst and is able to kill or disable it promptly.

At rest a bat’s head, especially the ears, is its most striking feature. The neck is likely to be short and relatively immobile. The projecting portion of the external ear (the pinna) is usually extremely large and often is funnel-shaped. In several genera that feed on terrestrial arthropods, the ears are particularly oversized, probably for highly precise directional assessment. A projection on the front side of the auditory canal (the tragus) or another on the rear side (antitragus) may also be conspicuous. The ears are often highly mobile, sometimes flicking back and forth in phase with the production of sonar signals. In some species the ears are immobile, but in all cases they probably function in tandem for directional analysis.

Bats often have a rodentlike or foxlike muzzle, but in many the face has a pushed-in puglike appearance. In the nectar feeders the snout is elongated to house the long extensible tongue. Many bats have a facial ornament, the nose leaf, which consists of skin and connective tissue. It surrounds the nostrils and extends as a free flap or flaps above the nostrils and in front of the face. The complexity and shape of the nose leaf varies with family; its presence correlates with nasal emission of orientation signals. Thus, it is supposed that the nose leaf influences sound output, perhaps by narrowing the beam, but evidence is sparse.
Most bats are well furred except for the wing membranes. Colours are generally shades of brown, tan, gray, or black on top and lighter shades on the underside. Red, yellow, or orange variants occur in many species. Speckled or mottled patterns are common, as are bright or light-coloured spots or stripes. Bright red, yellow, or orange shading on the head, neck, and shoulders is not unusual. Mottled fur may enable the bat to be inconspicuous on lichen-covered bark or rock. Bright spots may simulate the speckled sunlight of the forest canopy as seen from below. Stripes probably break up contours. The colouring seen while the animalis hanging may be a kind of countershading for concealment, or it may enhance the bat’s simulation of a ripening fruit or a dead leaf. Many bats that roost externally hang from a branch by one foot, which then looks like a plant stem.

Many bats have large dermal glands, the location of which depends on family. These glands secrete odorous substances that may serve as species or mating recognition signals (pheromones). Some glands may also supply oils for conditioning the skin or waterproofing the fur.

Thermoregulation

When fully active, bats have a body temperature of about 37 °C (98.6 °F). Although some bats maintain fairly even body temperatures, a large number undergo periodic raising or lowering of their temperature. Many of the vesper bats and horseshoe bats and a few free-tailed bats reduce their body temperature to that of their surroundings (ambient temperature) shortly after coming to rest. This condition is called heterothermy. They raise their temperature again on being aroused or when readying themselves for nocturnal foraging. The drop in body temperature, if the ambient temperature is relatively low, results in a lethargic state. Energy is conserved by thus “turning down the thermostat,” but the bat is rendered relatively unresponsive to threats by predators or weather. Heterothermic bats therefore generally roost in secluded sites offering protection, often in crevices. In heterothermic bats one or more sensory systems and the brain remain sensitive at low temperatures and initiate the necessary heat production for arousal. Heat is generated by the metabolism of fat and by shivering.

Many bats that exhibit daily torpor also hibernate during the winter and therefore must store energy as body fat. In the fall these bats increase their weight by 50 to 100 percent. They must also migrate from the summer roost to a suitable hibernation site (often a cave) that will remain cool and humid throughout the winter without freezing. Large populations often aggregate in such caves. Hibernation involves the absence of temperature regulation for long periods in addition to adaptations of circulation, respiration, and renal function and the suspension of most aspects of activity. Bats of hibernating species generally court and mate in the fall when they are at their nutritional peak. During pregnancy, lactation, and juvenile growth, bats probably thermoregulate differently, more closely approximating stability.
Bats of several tropical families maintain a constant body temperature (homeothermy). This, however, depends on the nutritional state as well. A spectrum of degrees of homeothermy and heterothermy probably will be discovered.

Digestion and water conservation

Digestion in bats is unusually rapid. They chew and fragment their food exceptionally thoroughly and thus expose a large surface area of it to digestive action. They may begin to defecate 30 to 60 minutes after beginning to feed and thereby reduce the load that must be carried in flight.
Some bats live in sun-baked roosts without access to water during the day. They may choose these roosts for their heat, and thus conserve their own, but it is not yet known how they hold their body temperature down without using water. In the laboratory, bats die if body temperature rises above about 40–41 °C (104–106 °F).

Senses

In folklore, bats have been considered to be blind. In fact, the eyes in the Microchiroptera are small and have not been well studied. Among the Megachiroptera the eyes are large, but vision has been studied in detail only in flying foxes. These bats are able to make visual discriminations at lower light levels than humans can. The Megachiroptera fly at night, of course, and some genera fly below or in the jungle canopy, where light levels are very low. Except for rousette bats (Rousettus), none are known to orient acoustically.

Studies of several genera of Microchiroptera have revealed that vision is used in long-distance navigation and that obstacles and motion can be detected visually. Bats also presumably use vision to distinguish day from night and to synchronize their internal clocks with the local cycle of daylight and darkness.

The senses of taste, smell, and touch in bats do not seem to be strikingly different from those of related mammals. Smell is probably used as an aid in locating fruit and flowers and possibly, in the case of vampire bats, large vertebrates. It may also be used for locating an occupied roost, members of the same species, and the differentiation of individuals by gender. Many bats depend upon touch, aided by well-developed facial and toe whiskers and possibly by the projecting tail, to place themselves in comforting body contact with rock surfaces or with other bats in the roost.

Evolution And Paleontology

The fossil record of bats prior to the Pleistocene Epoch (about 2,600,000 to 11,700 years ago) is limited and reveals little about bat evolution. Most fossils can be attributed to living families. Skulls and teeth compatible with early bats are known from about 60 million years ago, during the Paleocene Epoch. These specimens, however, may well have been from insectivores, from which bats are clearly distinguishable only on the basis of flight adaptations. By 45 million years ago (the Eocene Epoch), bats with fully developed powers of flight had evolved.

The order Chiroptera is readily divided into two suborders—Megachiroptera (large Old World fruit bats) and Microchiroptera (small bats). The Megachiroptera orient visually and exhibit a number of primitive skeletal features. The Microchiroptera orient acoustically. It is not certain that they have a common origin. The suborders either evolved separately from flightless insectivores or diverged very early in chiropteran history.

The two principal geographic centres of bat evolution appear to be the Australo-Malaysian region, with about 290 species, and the New World tropics, with about 230 species. Comparable ecological niches in the Old World and the New World are occupied largely by different genera of bats, usually of different families.

Classification

Distinguishing taxonomic features

The order Chiroptera is defined by flight and the elongated finger bones and marked pectoral specialization that support it. Weak pelvic and leg development is also a chiropteran feature. The ulna of the forearm is reduced; claws are absent on the fingers except on the thumb (and occasionally the second finger); and the knee is directed rearward and outward. The maximum complement of permanent teeth is 38, the minimum 20.

Annotated classification

The following classification is based on the third edition of ‘Mammal Species of the World’, edited by Don E. Wilson and DeeAnn M. Reeder, published in 2005. Subsequent research has shown, however, that the number of bat species continues to increase from the discovery of new forms and from the results of studies using DNA analysis to examine the evolutionary relationships between known bat species.

Jai Ganesh · 2019-05-18 00:09:01

343) Apricot

Apricot, (Prunus armeniaca), stone fruit of the family Rosaceae (order Rosales), closely related to peaches, almonds, plums, and cherries. Apricots are cultivated throughout the temperate regions of the world, especially in the Mediterranean. They are eaten fresh or cooked and are preserved by canning or drying. The fruit is also widely made into jam and is often used to flavour liqueurs. Apricots are a good source of vitamin A and are high in natural-sugar content. Dried apricots are an excellent source of iron.

Apricot trees are small and spreading, with broad ovate leaves that have pointed tips. The leaves are bright green in colour and are held erect on the twigs. The self-pollinated flowers are white in full bloom and borne singly or doubly at a node on very short stems. The fruits are drupes with a large, flat pit, or stone, within which is the seed. Similar in shape to a peach, the fruit is nearly smooth, round to oblong in some varieties, and somewhat flattened but with little to no hairiness when ripe. Its flesh is typically a rich yellow to yellowish orange. The seeds (also called kernels) of several varieties are sweet, though they are poisonous until roasted.

Apricots are propagated by budding on peach or apricot rootstocks, and peaches, plums, and apricots may be readily intergrafted. The tree succeeds in a well-drained loamy soil, preferably light rather than heavy. Most varieties withstand winter cold as well as peaches, but the blossom buds, opening earlier than those of the peach, are frequently killed by late freezes. The trees are quite drought-resistant and under favourable growing conditions are long-lived, some living 100 years or longer.

The apricot was originally domesticated in China but is now cultivated on every continent except Antarctica. Archaeological evidence shows that apricots were eaten in ancient Armenia, and they were first introduced to the New World in the early 18th century by Spanish missionaries in California. In 2011, the top five producers of apricots were Turkey, Iran, Uzbekistan, Italy, and Algeria.

Jai Ganesh · 2019-05-20 00:59:19

344) Bonsai

Bonsai, (Japanese: “tray-planted”) living dwarf tree or trees or the art of training and growing them in containers.

Bonsai specimens are ordinary trees and shrubs (not hereditary dwarfs) that are dwarfed by a system of pruning roots and branches and training branches by tying with wire. The art originated in China, where, perhaps over 1,000 years ago, trees were cultivated in trays, wooden containers, and earthenware pots and trained in naturalistic shapes. Bonsai, however, has been pursued and developed primarily by the Japanese. The first Japanese record of dwarfed potted trees is in the Kasuga-gongen-genki (1309), a picture scroll by Takashina Takakane.

The direct inspiration for bonsai is found in nature. Trees that grow in rocky crevices of high mountains, or that overhang cliffs, remain dwarfed and gnarled throughout their existence. The Japanese prize in bonsai an aged appearance of the trunk and branches and a weathered character in the exposed upper roots. These aesthetic qualities are seen to embody the philosophical concept of the mutability of all things.

Bonsai may live for a century or more and may be handed down from one generation to another as valued family possessions. Aesthetics of scale call for short needles on conifers and relatively small leaves on deciduous trees. Small-flowered, small-fruited varieties of trees are favoured. Open space between branches and between masses of foliage are also important aesthetically. In diminutive forests the lower portions of the trunks should be bare.

Good bonsai specimens are usually hardy species that can be kept outdoors the year round wherever winters are mild. They can be brought into the house occasionally for appreciation and enjoyment. In Japan they are customarily displayed in an alcove or on small tables in a living room and later returned to their outdoor bonsai stands.

The selection of the appropriate container in which to cultivate a bonsai is an essential element of the art. Bonsai pots are usually earthenware, with or without a colourful exterior glaze. They may be round, oval, square, rectangular, octagonal, or lobed and have one or more drainage holes in the bottom. Containers are carefully chosen to harmonize in colour and proportion with the tree. If the container is rectangular or oval, the tree is planted not quite halfway between the midpoint and one side, according to the spread of the branches. In a square or round container the tree is placed slightly off centre, except for cascade types, which are planted toward the opposite side of the container from which they overhang. Bonsai are trained to have a front, or viewing side, oriented toward the observer when on exhibit.

Although categorizations vary considerably, miniature bonsai are known broadly as shohin. The smallest of these (keishi and math) range in size up to about 2 inches (5–7 cm) in height and, started from seeds or cuttings, may take three to five years to come to quality stage. They may live several decades. Small bonsai (mame), 2 to 6 inches (7 to 15 cm) in height, require 5 to 10 or more years to train. Medium bonsai generally range from roughly 7 to 15 inches (20 to 40 cm) in height but can be up to about 2 feet (60 cm) tall and can be produced in as little as three years. Large (dai) bonsai can be as tall as 47 inches (120 cm) and require two or more people to move them.

Naturally dwarfed trees collected in the wild frequently fail to adapt to cultivation as bonsai because of the severe shock brought about by the change of environment and substrate.

Bonsai must be repotted every one to five years, depending on the species and extent of root growth. Gradual root pruning during transplanting in subsequent years reduces the size of the soil ball so that the tree can ultimately go into the desired small and shallow container. Water is usually provided on a daily basis; liquid fertilizer is also used. Pruning and nipping of shoots is performed through the growing season.

A bonsai industry of considerable size exists as part of the nursery industry in sections of Japan. The technique is also pursued on a small industrial scale in California.

Jai Ganesh · 2019-05-22 00:04:09

345) Octopus

Octopus, plural octopuses or octopi, in general, any eight-armed cephalopod (octopod) mollusk of the order Octopoda. The true octopuses are members of the genus Octopus, a large group of widely distributed shallow-water cephalopods.

Octopuses vary greatly in size: the smallest, O. arborescens, is about 5 cm (2 inches) long, while the largest species may grow to 5.4 metres (18 feet) in length and have an arm span of almost 9 metres (30 feet). The typical octopus has a saccular body: the head is only slightly demarcated from the body and has large, complex eyes and eight contractile arms. Each arm bears two rows of fleshy suckers that are capable of great holding power. The arms are joined at their bases by a web of tissue known as the skirt, at the centre of which lies the mouth. The latter organ has a pair of sharp, horny beaks and a filelike organ, the radula, for drilling shells and rasping away flesh.
The octopus takes water into its mantle and expels the water after respiration through a short funnel or siphon. Most octopuses move by crawling along the bottom with their arms and suckers, though when alarmed they may shoot swiftly backward by ejecting a jet of water from the siphon. When endangered they eject an inky substance, which is used as a screen; the substance produced by some species paralyzes the sensory organs of the attacker.

The best-known octopus is the common octopus, O. vulgaris, a medium-sized animal that is widely distributed in tropical and temperate seas throughout the world. It lives in holes or crevices along the rocky bottom and is secretive and retiring by nature. It feeds mainly on crabs and other crustaceans. This species is thought to be the most intelligent of all invertebrate animals. O. vulgaris has highly developed pigment-bearing cells and can change its skin colours to an astonishing degree with great rapidity. Each pigment-bearing cell (chromatophore) is individually innervated from the brain.

The veined octopus (Amphioctopus marginatus) is also known for its intelligence. In 2009 biologists reported having observed the animals excavating coconut half shells from the ocean floor and carrying them for use as portable shelters. Such behaviour is regarded by biologists as the first documented example of tool use by an invertebrate.

Octopuses have separate genders, and the male has a specially modified arm, called a hectocotylus, by means of which it inserts spermatophores, or packets of male gamette, directly into the female’s mantle cavity. O. vulgaris mates during the winter, and the eggs, about 0.3 cm (1/8 inch) long, are laid under rocks or in holes, the total number of eggs amounting to more than 100,000. During the four to eight weeks required for the larvae to hatch, the female guards the eggs, cleaning them with her suckers and agitating them with water. Upon hatching, the tiny octopods, which closely resemble their parents, spend several weeks drifting in the plankton before taking refuge on the bottom.

Octopuses feed mainly upon crabs and lobsters, although some are plankton feeders, and they are fed upon by a number of marine fishes. They have long been considered a culinary delicacy by peoples of the Mediterranean, East Asia, and other parts of the world.

(Cephalopod, any member of the class Cephalopoda of the phylum Mollusca, a small group of highly advanced and organized, exclusively marine animals. The octopus, squid, cuttlefish, and chambered nautilus are familiar representatives. The extinct forms outnumber the living, the class having attained great diversity in late Paleozoic and Mesozoic times. The extinct cephalopods are the ammonites, belemnites, and nautiloids, except for five living species of Nautilus.)

Jai Ganesh · 2019-05-23 14:17:06

346) Peach

Peach, (Prunus persica), fruit tree of the rose family (Rosaceae), grown throughout the warmer temperate regions of both the Northern and Southern hemispheres. Peaches are widely eaten fresh as a dessert fruit and are also baked in pies and cobblers; canned peaches are a staple commodity in many regions. Yellow-fleshed varieties are especially rich in vitamin A.

The peach probably originated in China and then spread westward through Asia to the Mediterranean countries and later to other parts of Europe. The Spanish explorers took the peach to the New World, and as early as 1600 the fruit was found in Mexico. For centuries the cultivation and selection of new varieties of peaches were largely confined to the gardens of the nobility, and large-scale commercial peach growing did not begin until the 19th century, in the United States. The early plantings were seedling peaches, inevitably variable, and often of poor quality. The practice of grafting superior strains onto hardy seedling rootstocks, which came later in the century, led to the development of large commercial orchards.

Small to medium-sized, peach trees seldom reach 6.5 metres (21 feet) in height. Under cultivation, however, they are usually kept between 3 and 4 metres (10 and 13 feet) by pruning. The leaves are glossy green, lance-shaped, and long pointed; they usually have glands at their bases that secrete a fluid to attract ants and other insects. The flowers, borne in the leaf axils, are arranged singly or in groups of two or three at nodes along the shoots of the previous season’s growth. The five petals, usually pink but occasionally white, five sepals, and three whorls of stamens are borne on the outer rim of the short tube, known as the hypanthium, that forms the base of the flower.

The peach develops from a single ovary that ripens into both a fleshy, juicy exterior that forms the edible part of the fruit and a hard interior, called the stone or pit, that encloses the seed(s). Of the two ovules in the female organ of flower, usually only one becomes fertilized and develops into a seed. This frequently results in one half of the fruit being slightly larger than the other. The flesh may be white, yellow, or red. Varieties may be freestone types, which have stones that separate easily from the ripe flesh, or clingstones, which have flesh that adheres firmly to the stone. The skin of most ripe peaches is downy or fuzzy; peaches with smooth skins are called nectarines. Most peach varieties produce more fruits than can be maintained and developed to full size. Some shedding of fruitlets takes place naturally, about a month to six weeks after full bloom, but the number remaining may have to be reduced further by hand thinning.

Peach trees are relatively short-lived as compared with some other fruit trees. In some regions orchards are replanted after 8 to 10 years, while in others trees may produce satisfactorily for 20 to 25 years or more, depending upon their resistance to diseases, pests, and winter damage. They are intolerant of severe cold and cannot be grown successfully where temperatures normally fall to −23 to −26 °C (−10 to −15 °F). On the other hand, they do not grow satisfactorily where the winters are too mild, and most varieties require some winter chilling to induce them to burst into growth after the annual dormant period. The peach does well on various soil types but in general it grows best on well-drained sandy or gravelly loams. On most soils the peach responds well to nitrogen-rich fertilizers or manures, without which satisfactory growth cannot be obtained. Trees are usually pruned annually to prevent them from becoming too tall; the upright shoots are pruned back to outgrowing laterals to produce a spreading tree and keep it open to sunlight.

Thousands of varieties of the peach have been developed. Yellow-fleshed varieties such as Elberta, Redhaven, and Halford are preferred in North America, while both yellow- and white-fleshed types are popular in Europe. Worldwide, the peach is one of the most important of the deciduous-tree fruits, and China, Italy, Spain, and the United States are major producers.

Jai Ganesh · 2019-05-24 00:16:25

347) Bear

Bear, (family Ursidae), any of eight species of large short-tailed carnivores found in the Americas, Europe, and Asia. The sun bear(Helarctos malayanus) is the smallest, often weighing less than 50 kg (110 pounds), and the largest is a subspecies of Alaskan brown bearcalled the Kodiak bear (Ursus arctos middendorffi; see grizzly bear). The polar bear (Ursus maritimus), however, is the largest bear species. The black bear (Ursus americanus) is common in parts of the United States and Canada.

Bears are generally omnivorous, but dietary preferences range from seals for the entirely carnivorous polar bear to assorted vegetation for the largely herbivorous spectacled bear (Tremarctos ornatus). The giant panda (Ailuropoda melanoleuca) eats only bamboo. Usually gaining weight beforehand, most bears sleep fitfully through much of the winter, but they do not truly hibernate. Despite their bulk, most bears climb with ease and swim strongly.

Natural History

Ursids are mainly animals of northern temperate regions and are found farther north than any other mammal. The Arctic fox is found as far north on land, but the polar bear regularly roams on sea ice hundreds of kilometres from shore. Africa and Australia lack bears entirely. The spectacled bear of the South American Andes Mountains is the only species that lives south of the Equator.

Although clumsy in appearance, bears can move surprisingly fast, even through dense cover that would seriously impede a human or a horse. Their senses of sight and hearing, however, are poorly developed, and most hunting is done by smell. Some, such as black and spectacled bears, are strong climbers, and all are strong swimmers, most notably the polar bear. Bears do not generally communicate by sound and usually are quiet, but they do growl at times when feeding, when being challenged by another bear or by humans, and when competing for mates.

Except for the carnivorous polar bear and the vegetarian giant panda, ursids are omnivorous, consuming many items that seem small for an animal of such large size. Ants, bees, seeds of trees, roots, nuts, berries, insect larvae such as grubs, and even the dainty dogtooth violet are eaten. Many bears relish honey, and the sun bear is sometimes called the “honey bear” because of this. Prey taken by bears include rodents, fish, deer, pigs, and seals. Grizzlies (North American subspecies of the brown bear, Ursus arctos) are known for their skillful fishing during the spawning runs of salmon. The polar bear’s diet is dictated by the Arctic environment, as little vegetation grows within its range. The Asian sloth bear (Melursus ursinus) delights especially in raiding and destroying termite nests, sucking up termites and larvae with its funnel-like lips. The giant panda has a special bone formation of the forefoot that functions as a sixth digit; it is opposable to the other five and thus is useful in handling bamboo.

Most bears, including the American and Asiatic black bears (Ursus americanus and U. thibetanus), eat large amounts of food before entering a den for a period of deep sleep during the winter. The polar bear digs a den in the snow, whereas grizzlies build large mounds of dirt in front of their dens. Bears, however, lack the physiological characteristics (lower heart rate, body temperature, breathing rate, and blood pressure) exhibited by animals that truly hibernate.

Male polar bears sometimes aggregate; otherwise bears are solitary, except during the mating season. Then they tend to congregate, pair off, and mate in seclusion. The male leaves the female soon after mating and plays no role in raising the young. Gestation periods vary, the fertilized egg remaining dormant in the uterus (delayed implantation), which ensures the birth of young while the female is in the winter den and guarantees that the cubs will emerge from the den in the spring, when food is abundant. Ursids breed once per year at most, and many bears breed only every two to four years. The breeding season is usually in late spring or early summer. Delayed implantation results in most births occurring in January or February. Newborn bears weigh about half a kilogram (one pound) and are about 23 cm (9 inches) long from the nose to the tip of the short tail. Twins are most common in bears, but up to five young may be produced. The cubs nurse for a few months and stay with the female until the next breeding (about a year and a half or more after birth). Most young, however, can get along on their own by about six months of age. Bears reach breeding condition at three and a half to six years of age, males usually maturing later than females. Longevity of bears in the wild ranges from 15 to 30 years, but in captivity they can live considerably longer.

Because of their large size, bears have few natural enemies in the wild. Most mortality occurs because of hunting by humans. On occasion, bears that fail to accumulate enough fat to last throughout the winter may die of starvation. Young bears are more vulnerable to predation because of their smaller size and thus may be killed by other carnivores such as wolves or cougars but most importantly by other bears, especially males. For this reason, females with cubs are highly protective of their young in the vicinity of males.

Home ranges occupied by individual bears vary in size depending on the abundance of food, and larger areas are used when food is in short supply. Although highly variable among geographic areas and even among seasons, American black bears roam areas of 40 to 200 square km (15 to 77 square miles), grizzlies about 300–700 square km. Some polar bears trek across ranges of more than 125,000 square km (48,000 square miles).

Importance To Humans

If taken when young, bears can be tamed quite easily and are commonly used in circus animal acts. This has often caused people to consider bears as tame and harmless rather than as potentially dangerous creatures deserving wariness and respect. This mistake has frequently resulted in tragedy for both humans and bears. Grizzly and polar bears are the most dangerous, but Eurasian brown bears and American black bears have also been known to attack humans. Some species depredate livestock on occasion, and some ursids, such as Asiatic and American black bears, may destroy fruit or other crops, especially corn.

The pelts of bears have been used for a number of purposes. Perhaps most popular has been the bearskin rug. Skins also have been used for fashionable articles of clothing. The meat of black and polar bears often is consumed. The teeth and claws of bears have been favourite ornaments among native American peoples, and the fat furnishes “bear grease,” which is used for cooking. The gall bladders of Asian bears are greatly valued in Asia for pharmaceutical purposes.

Form And Function

In most species, the male is larger than the female. Unlike cats and canids such as dogs and wolves, bears walk in plantigrade fashion (on the soles of their feet with the heels touching the ground). Each foot has five digits ending in large nonretractile claws that are sometimes adapted for digging, as in the Asian sloth bear. The claws on the front feet are usually better developed than those on the rear, and they are especially adapted for digging out small rodents or nutritious plant roots. The feet generally have hairless soles, but those of the polar bear are covered with hair, enabling the animal to walk on ice with a firm footing. Bears lack a clavicle but have a baculum. Their lips are protrusible and mobile. All have a short stubby tail.

Bears have an elongate skull that is especially heavy in the back portion, and their jaws are controlled at the hinge by a powerful set of muscles. The teeth of the omnivorous bears are unspecialized. The first three premolars are usually either missing or extremely small. Except for variability as to the presence of premolars, the ursid dental formula is that of the Carnivora generally, but the sloth bear lacks one pair of upper incisors. The shearing teeth (carnassials) are poorly developed, and the molars have broad, flat crowns.

Evolution And Classification

The bear family is the most recently evolved lineage of carnivores. Its ancestral line appears to have diverged from canid stock during the Late Miocene Epoch and to have developed into modern species through such Pliocene forms as Hyaenarctos of Europe, Asia, and North America. Studies of mitochondrial DNA (mtDNA) performed during the early 21st century showed that black bears, brown bears, and polar bears diverged from one another some 4 million–5 million years ago, early in the Pliocene Epoch (5.3 million to 2.6 million years ago).

There has been much disagreement over the classification of giant pandas. Mammalogists have placed giant pandas with bears (family Ursidae), with raccoons (Procyonidae), or with the red, or lesser, panda(Ailurus fulgens) in Ailuridae. However, molecular analyses performed during the 1990s have revealed a close evolutionary relationship between giant pandas and bears.

Jai Ganesh · 2019-05-26 00:52:39

348) Sea horse

Sea horse, (genus Hippocampus), any of about 36 species of marine fishes allied to pipefishes in the family Syngnathidae (order Gasterosteiformes). Sea horses are found in shallow coastal waters in latitudes from about 52° N to 45° S. Their habitats include coral reefs, mangroves, sea grass beds, and estuaries. They are unique in appearance, with their horselike head, prehensile tail, independently moving eyes, and brood pouch. They have long, tubular snouts and small, toothless mouths. Their bodies are covered with consecutive rings of bony plates. The name of the genus that contains sea horses is taken from the Greek words hippos (meaning “horse”) and kampos (meaning “sea monster”).

Sea horses vary in size, ranging in length from about 2 to 35 cm (about 0.8 to 14 inches). The smallest species, Denise’s pygmy sea horse (H. denise), is found in the tropical western Pacific from Indonesiato Vanuatu. The largest species, the pot-bellied sea horse (H. abdominalis), inhabits the waters off South Australia and New Zealand.

Sea horses are rather immobile, swimming more slowly than other fishes. When swimming they maintain a vertical position and propel themselves forward using a soft-rayed dorsal fin. They use pectoral fins located on the side of the head to maneuver. Some scientists contend that this upright swimming posture evolved shortly after the expansion of sea grasses in the western Pacific roughly 25 million years ago. These plants provided sea horses with useful hiding places to avoid enemies and to capture unsuspecting prey, and ancestors of the sea horse evolved to maximize the opportunities offered by this new habitat.

Sea horses are usually found clinging to plants or corals with their tails. Their sedentary habits coupled with excellent camouflage abilities render them successful ambush predators. When small organisms swim nearby, a sea horse may capture them by rapidly sucking them into the mouth. Sea horses also rely upon camouflage to avoid predators such as crabs and other fish.

The reproductive behaviour of sea horses is notable in that the male carries the fertilized eggs. After an elaborate courtship, the female uses an ovipositor (egg duct) to place her eggs into a brood pouch located at the base of the male’s tail where the eggs are later fertilized. Depending on the species, the eggs remain in the pouch between 10 days and 6 weeks. During this time the male nurtures the developing young by regulating the chemistry of the fluid inside the pouch, slowly transforming it from that of his internal body fluids to that of salt water as pregnancy progresses. To nourish the growing young, the male also produces inorganic compounds and releases the hormone prolactin, which helps break down the proteins contributed by the female. Once the eggs hatch, the male convulses his body and expels the young through a single opening in the pouch. The young are miniature versions of their parents that receive no further care. The male can receive another brood of eggs almost immediately after giving birth. In some species a male and female will maintain a monogamous pair bond throughout the breeding season and produce many broods.

Commercially, sea horses are traded live as aquarium animals and dead for use in traditional medicines and as curios. Threatened by direct overfishing, accidental capture (by catch) in other fisheries, and the destruction of their coastal habitats, some species—such as the Pacific sea horse (H. ingens)—face extinction.

Jai Ganesh · 2019-05-28 00:01:50

349) Leaning Tower of Pisa

Leaning Tower of Pisa, Italian Torre Pendente di Pisa, medieval structure in Pisa, Italy, that is famous for the settling of its foundations, which caused it to lean 5.5 degrees (about 15 feet [4.5 metres]) from the perpendicular in the late 20th century. Extensive work was subsequently done to straighten the tower, and its lean was ultimately reduced to less than 4.0 degrees.

The bell tower, begun in 1173 as the third and final structure of the city’s cathedral complex, was designed to stand 185 feet (56 metres) high and was constructed of white marble. Three of its eight stories had been completed when the uneven settling of the building’s foundations in the soft ground became noticeable. At that time, war broke out between the Italian city-states, and construction was halted for almost a century. This pause allowed the tower’s foundation to settle and likely prevented its early collapse.

Giovanni di Simone, the engineer in charge when construction resumed, sought to compensate for the lean by making the new stories slightly taller on the short side, but the extra masonry caused the structure to sink still further. The project was plagued with interruptions, as engineers sought solutions to the leaning problem, but the tower was ultimately topped out in the 14th century. Twin spiral staircases lined the tower’s interior, with 294 steps leading from the ground to the bell chamber (one staircase incorporates two additional steps to compensate for the tower’s lean). Over the next four centuries the tower’s seven bells were installed; the largest weighed more than 3,600 kg (nearly 8,000 pounds). By the early 20th century, however, the heavier bells were silenced, as it was believed that their movement could potentially worsen the tower’s lean.

The foundations have been strengthened by the injection of cement grout and various types of bracing and reinforcement, but in the late 20th century the structure was still subsiding, at the rate of 0.05 inch (1.2 mm) per year, and was in danger of collapse. In 1990 the tower was closed and all the bells silenced as engineers undertook a major straightening project. Earth was siphoned from underneath the foundations, decreasing the lean by 17 inches (44 cm) to 13.5 feet (4.1 metres); the work was completed in May 2001, and the structure was reopened to visitors. The tower continued to straighten without further excavation, until in May 2008 sensors showed that the motion had finally stopped, at a total improvement of 19 inches (48 cm). Engineers expected the tower to remain stable for at least 200 years.

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