Math Is Fun Forum

Hi,

#2460. What does the medical term Laryngeal mask airway signify?

Hi,

#6233.

Hi,

Well done!

2575.

Hi,

#10545. What does the term in Biology Cell wall mean?

#10546. What does the term in Biology Centriole mean?

Hi,

#2459. What does the medical term Landau reflex mean?

Hi,

#6232.

2380) Penguin

Gist

A penguin is a flightless, black-and-white seabird found almost exclusively in the Southern Hemisphere, known for its adaptations to marine life, including flippers for swimming, dense feathers for warmth, and a diet of fish and krill. While most live in cold Antarctic or sub-Antarctic regions, the Galápagos penguin lives near the equator. Penguins are excellent swimmers and divers, using their short, paddle-like wings to propel themselves through the water, and their contrasting dark backs and white bellies provide camouflage.

Penguins primarily live in the Southern Hemisphere, inhabiting cold environments like Antarctica, subantarctic islands, and temperate coasts in countries such as Australia, New Zealand, and South Africa. While most species are found in these southern regions, the Galápagos penguin is an exception, living on islands near the equator in the warm waters off the coast of Ecuador. All penguins require proximity to the ocean for food and to raise their young on land.

Summary

Penguins are a group of aquatic flightless birds from the family Spheniscidae of the order Sphenisciformes. They live almost exclusively in the Southern Hemisphere. Only one species, the Galápagos penguin, is equatorial, with a small portion of its population extending slightly north of the equator (within a quarter degree of latitude). Highly adapted for life in the ocean water, penguins have countershaded dark and white plumage and flippers for swimming. Most penguins feed on krill, fish, squid and other forms of sea life which they catch with their bills and swallow whole while swimming. A penguin has a spiny tongue and powerful jaws to grip slippery prey.

They spend about half of their lives on land and the other half in the sea. The largest living species is the emperor penguin (Aptenodytes forsteri): on average, adults are about 1.1 m (3 ft 7 in) tall and weigh 35 kg (77 lb). The smallest penguin species is the little blue penguin (Eudyptula minor), also known as the fairy penguin, which stands around 30–33 cm (12–13 in) tall and weighs 1.2–1.3 kg (2.6–2.9 lb). Today, larger penguins generally inhabit colder regions, and smaller penguins inhabit regions with temperate or tropical climates. Some prehistoric penguin species were enormous: as tall or heavy as an adult human. There was a great diversity of species in subantarctic regions, and at least one giant species in a region around 2,000 km south of the equator 35 mya, during the Late Eocene, a climate decidedly warmer than today.

Details

A penguin is (order Sphenisciformes), any of 18–21 species of flightless marine birds that live only in the Southern Hemisphere. The majority of species live not in Antarctica but rather between latitudes 45° and 60° S, where they breed on islands. A few penguins inhabit temperate regions, and one, the Galapagos penguin (Spheniscus mendiculus), lives at the Equator.

General features:

The world's deepest-diving birds

The world's deepest-diving birdsEmperor penguins (Aptenodytes forsteri) live in colonies along the coastline of Antarctica. They are capable of diving to depths of about 550 metres (1,800 feet) in search of food, which makes them Earth's deepest-diving birds.

The stocky, short-legged appearance of penguins has endeared them to people worldwide. They range from about 35 cm (14 inches) in height and approximately 1 kg (about 2 pounds) in weight in the blue, or fairy, penguin (Eudyptula minor) to 115 cm (45 inches) and 25 to 40 kg (55 to 90 pounds) in the emperor penguin (Aptenodytes forsteri). Most are black on the back and white below, often with lines of black across the upper breast or spots of white on the head. Colour is rare, being limited to red or yellow irises of the eye in some species; red beaks or feet in a few; yellow brow tufts in the three species of Eudyptes; and orange and yellow on the head, neck, and breast in the emperor and king (A. patagonica) penguins.

The total populations of some species, such as the emperor, are estimated in the hundreds of thousands, but most species of smaller penguins certainly run into the millions. Immense island breeding colonies, some teeming with hundreds of thousands of nesting pairs, represent a large potential food resource, but the economic importance of penguins is negligible. Nineteenth-century whalers and seal hunters visited some colonies for meat and eggs, and a penguin oil industry once took large numbers of the birds. By the early 20th century, however, this exploitation was no longer profitable, and most colonies were left alone or actively protected. Some species are now increasing in numbers, apparently as a result of the mid-20th century’s decimation of Antarctic whales, which compete with penguins for the krill (minute crustaceans) on which both feed. Penguin populations, however, are highly vulnerable to changes in climate and ocean temperature, including recent global warming. Penguins also are very sensitive to depletion of local fish populations by humans.

Natural history:

Reproduction

Many features of the penguin life cycle vary with body size and geographic distribution; the chronology of breeding may also vary within a species in relation to latitude. The majority of species breed only once each year. Certain species, such as the African penguin (Spheniscus demersus), probably other members of this genus, and the blue penguin, breed twice a year. The king penguin breeds twice in three years. One egg is laid by the emperor and king penguins; all others lay two or occasionally three. Most penguins begin breeding in the austral (southern) spring or summer. King penguins are on a 14- to 18-month cycle, and the timing of an individual pair depends on the success or failure of the previous breeding attempt. Some populations of the gentoo penguin (Pygoscelis papua) also breed in winter. The breeding of the emperor penguin begins in autumn, apparently timed so that the long developmental period will produce the young in midsummer, when their chances of survival are greatest.

The gentoo, which has a circumpolar distribution, is notable for its lack of synchrony among populations, but otherwise its breeding schedule is essentially comparable to that of most other species. In the Crozet Islands off southern Africa, for example, egg laying takes place in July. The two eggs are incubated for 35 or 36 days, and the rearing of the chick takes two months. The last immature birds go to sea in January.

Many types of visual and vocal displays are employed between the arrival of the birds at the colony and their departure. Courtship calls are used during pairing and to a lesser degree during the succeeding phases of breeding. There are marked vocal differences between sexes in the emperor penguin and the king penguin and less-marked dimorphisms in some other species. Upon arrival at the colony each bird returns to the nest that it left the previous year and generally rejoins its mate of the previous year, unless the death of the latter forces it to choose another partner. This applies even to the emperor penguin, which is capable of finding its mate despite the absence of a nest and the large size of the colony.

The displays that occur with the reassembly of the colony and the finding of mates, as well as those preceding copulation, are quite similar among the majority of species, but the accompanying vocalizations are more diverse. Various species have been described as trumpeting, croaking, cackling, and cooing; members of the genus Spheniscus are called jackass penguins for the braying sounds they make. The behaviour of experienced older birds is more elaborate and more effective than that of younger individuals. For example, Adélie penguins (Pygoscelis adeliae) may return to the reproductive colony from their third year onward but do not breed successfully until their fifth or sixth year.

Incubation of eggs is performed by both sexes in all species except the emperor penguin, in which it is done exclusively by the male, and it is begun immediately after egg laying. With the advent of incubation, the bustle and myriad cries that characterized mating give way to quiet and inactivity. Faulty incubation behaviour by inexperienced birds frequently results in the abandonment or breakage of eggs. The mortality rate (eggs and chicks) is very important at the egg stage, varying from year to year depending on climatic conditions, the percentage of young birds in the reproductive population, and the pressure of predation. In general, mortality (eggs and chicks) is from 40 to 80 percent of the eggs laid. In coastal colonies predators include, in order of importance: skuas, sheathbills, and the giant petrel. On the Australian, African, and South American continents, the nocturnal habits of certain penguins and the fact that they nest in burrows substantially limit predation, which is mostly by gulls and man.

Following egg laying, the female usually departs for the sea to feed, returning to relieve her mate after about 10 to 20 days. Thereafter, father and mother alternate in periods of a week or two. The female emperor penguin, however, must often walk 80 to 160 km (50 to 100 miles) from the colony to the sea and does not return until the end of the incubation period. During the 64-day incubation period, which extends through the height of the Antarctic winter, the male emperor penguin incubates the egg, holding it on his feet and living on stored fat reserves. During violent winter storms, members of the colony gather for mutual protection from wind and cold in tightly packed crowds called huddles.

Emergence from the shell takes 24 to 48 hours, during which the brooding parent is particularly irritable. The chick shows feeding behaviour immediately on hatching, receiving a regurgitated “soup” of crustaceans or fish by inserting its bill into the open mouth of the parent. During its early days the young bird is sheltered under the body of one of its parents, who take turns foraging and brooding. Growing larger, the young bird remains at a parent’s side, although the fledgling is able to maintain its body heat and move about alone. The chick then joins 100 or more of its contemporaries in a nursery group, or crèche, sometimes guarded by a few adults, while both its parents forage at sea. Upon returning with food, the parent calls its chick from the crèche and is able to distinguish it from other chicks (which frequently respond) by voice and appearance.

During the breeding season the number of “unemployed” adults in the colony increases with the addition of those who have lost eggs or chicks. In emperor penguin colonies, these unemployed birds often interfere with parents that have young and cause increased mortality. During the crèche stage the fuzzy down that has covered the chick since hatching is replaced by a coat of short stiff feathers, which are similar to those of the adult but usually somewhat different in colour. Once this molt is complete, the juvenile leaves the colony to seek its own food at sea.

The period of growth of the young bird from hatching to complete independence varies from two months, in the smallest species of the genus Eudyptula, to 51/2 months in the emperor and 12 to 14 months in the king penguin.

Adult penguins molt all of their feathers once a year following the breeding period. While in molt the bird is unable to enter the water and instead withdraws to a communal molting site usually situated in a sheltered area away from the colony. The duration of the molt varies from about two weeks in small species to more than a month in the larger ones.

The principal enemies of penguins at sea are the leopard seal and the killer whale (orca). Seals also take penguins near Australia, New Zealand, and other subantarctic regions.

Locomotion and orientation

Penguins are adapted for rapid locomotion in water, in which the wings, or flippers, are used for propulsion; the birds “fly” underwater. When moving at high speed, they frequently leave the water in leaps that may carry them a metre or more through the air; it is during this time that they breathe.

On land, penguins are much more awkward, even amusing, as they rock from side to side as they walk. Despite their short legs, however, penguins can run with surprising speed. Some, such as the northern rockhopper (Eudyptes moseleyi), the southern rockhopper (E. chrysocome), and Adélie penguins, move among rocks with agility, using the flippers for balance. On snow or ice, many penguins “toboggan,” sliding on the belly as they propel themselves with the feet and flippers. The flippers, along with the beak, are the prime weapons in defense and attack.

Scientists have long wondered how penguins are able to find their way back to their colonies from far out at sea, where currents may have carried them great distances. Also perplexing is how they are able to direct themselves correctly on land in the absence of clear-cut landmarks. Studies of penguins transported to the interior of Antarctica have found that they are able to find their way back to the ocean by using the sun as a directional aid. It is probable that the same means of orientation is used at sea. Upon approaching the coast they are able to recognize features of the shoreline and ocean bottom.

Food habits

The type of food utilized varies with the species, the geographic region, and the time of year. Most of the smaller southern penguins feed primarily upon krill, which attain high densities in the rich, well-oxygenated Antarctic waters. Cephalopods (squid and cuttlefish) and small fishes may form substantial fractions of the food, and in a few, such as the African penguin, fish is the basic element of the diet. The total weight of food consumed by a large penguin colony is prodigious, often exceeding several tons per day.

Form and function

The penguins are highly specialized for their flightless aquatic existence. The feet are located much farther back than those of other birds, with the result that the bird carries itself mostly upright; its walk can thus be described as plantigrade (i.e., on the soles). The sole comprises the whole foot instead of just the toes, as in other birds. The most notable characteristic of the group is the transformation of the forelimb into a paddle. This is accompanied by a body morphology particularly adapted to movement in a liquid medium. The thoracic (rib) cage is well developed, and the sternum bears a pronounced keel for the attachment of the pectoral muscles, which move the flippers. The flipper has the same skeletal base as the wing of flying birds but with its elements shortened and flattened, producing a relatively rigid limb covered with very short feathers—an ideal organ for rapid propulsion. The body plumage likewise consists of very short feathers, which minimize friction and turbulence. The density of the plumage and the layer of air that it retains provide almost complete insulation of the body.

Insulation of the bird’s body is particularly important for Antarctic species that live in water that is always below 0 °C (32 °F). The cooling power of seawater at −1.9 °C (28.6 °F) is equal to that of a temperature of −20 °C (−4 °F) with a wind of 110 km (70 miles) per hour. The skin is insulated by a layer of air trapped under the plumage, and the only bare skin in direct contact with the water is that of the feet. In the case of the emperor penguin on land, the feet are in almost constant contact with ice. The skin temperature is in the neighbourhood of 0 °C, and snow does not melt upon contact. This is possible because of remarkable anatomical arrangements in the lower limb, whereby closely adjacent arteries and veins form a system of heat exchange between opposing flows of blood. This arrangement permits cooled blood from the feet to absorb heat from outflowing blood, providing maximum economy of heat consistent with the functioning of the foot.

Like other seabirds, penguins have salt glands that enable them to ingest salt from seawater. Excess chloride is excreted in the form of a solution the concentration of which is greater than that of seawater. These glands are located above the eyes and are already functional in the young chick, which begins to consume food of marine origin from its first day of life.

Recent research has shown that the species most isolated geographically, such as the emperor penguin, can be subject to diseases. Some, such as the Adélie penguin, carry in their bodies trace amounts of pollutants, albeit in lower quantities than are found in many birds that live closer to humans.

Evidence from paleontology indicates that the penguins and the order Procellariiformes (albatrosses, shearwaters, and petrels) had a common origin. Both groups are represented by well-defined fossils dating to about 50 million years ago. The flightless sphenisciform line produced a number of distinctive side branches, all recognizably penguins, some giant in size. All of the fossil remains of penguins have been collected within the zone of the present-day distribution of the Sphenisciformes. Some apparently lived in warmer regions than do most of today’s penguins.

Phylogenetic analysis of living and fossil penguins shows that the group evolved a large body size early in its history. For example, two of the largest fossil penguins known—Icadyptes, which stood some 1.5 metres (about 5 feet) tall, and math, which stood about 1.8 metres (6 feet) tall—date to the Eocene Epoch (56 million to 33.9 million years ago). Living penguins make up a separate lineage characterized by smaller, highly aquatic species that began about 8 million years ago. The comparatively small size of living penguins is thus a geologically recent phenomenon that postdates the original radiation of giant penguins.

Additional Information

Penguins are a family of 17 to 19 species of birds that live primarily in the Southern Hemisphere. They include the tiny blue penguins of Australia and New Zealand, the majestic emperor penguins of Antarctica and king penguins found on many sub- Antarctic islands, the endangered African penguin and the Galápagos penguin—the only penguin to be found north of the equator.

Though they are birds, penguins have flippers instead of wings. They cannot fly and on land they waddle walking upright—though when snow conditions are right they will slide on their bellies. In the water they are expert swimmers and divers, and some species can reach speeds of up to 15 miles per hour. The penguin’s distinctive coloring—black body with white belly—helps camouflage the bird in the water as it searches for meals of small shrimp, fish, crabs and squid.

Hi,

You are correct! Good work!

Post once a day in 'Compute the solution'.

2573.

2379) Bluff (Geography)

Gist

In geography, a bluff is a high, steep slope or cliff that typically overlooks a body of water, formed by the erosion of the outer bank of a river's meander or along a coastline. The term can also refer to a clump of trees, particularly willows or poplars, found on the flat Canadian prairies, which is a different meaning from the geological landform.

Although any cliff with a broad, steep face may be called a bluff, the term bluff refers to a high bank or bold headland with a broad, precipitous, sometimes rounded cliff face. Bluffs can overlook either a plain or a body of water, especially on the outside curve of a stream meander.

Summary

In geography and geology, a cliff or rock face is an area of rock which has a general angle defined by the vertical, or nearly vertical. Cliffs are formed by the processes of weathering and erosion, with the effect of gravity. Cliffs are common on coasts, in mountainous areas, escarpments and along rivers. Cliffs are usually composed of rock that is resistant to weathering and erosion. The sedimentary rocks that are most likely to form cliffs include sandstone, limestone, chalk, and dolomite. Igneous rocks such as granite and basalt also often form cliffs.

An escarpment (or scarp) is a type of cliff formed by the movement of a geologic fault, a landslide, or sometimes by rock slides or falling rocks which change the differential erosion of the rock layers.

Most cliffs have some form of scree slope at their base. In arid areas or under high cliffs, they are generally exposed jumbles of fallen rock. In areas of higher moisture, a soil slope may obscure the talus. Many cliffs also feature tributary waterfalls or rock shelters. Sometimes a cliff peters out at the end of a ridge, with mushroom rocks or other types of rock columns remaining. Coastal erosion may lead to the formation of sea cliffs along a receding coastline.

The British Ordnance Survey distinguishes between cliffs (continuous line along the topper edge with projections down the face) and outcrops (continuous lines along lower edge).

Details:

What Is A Bluff In Geography?

A bluff is a ridge of land that extends into the air. The term is commonly used in geography to refer to high ground. Bluffs are often situated at the foot of steep cliffs and mountains.

A bluff is a steep hill or cliff, especially one that appears close to its base. It can also refer to an area where the slope is so steep that it appears to be an unbroken cliff.

A typical bluff is situated at the foot of steep cliffs and mountains.

Why Is A Bluff Called A Bluff?

A bluff is a cliff, small hill, or other elevation on the side of a mountain or hill, that rises steeply from the ground, usually without trees or shrubs.

Bluffs are called bluff because they appear to be higher than they actually are. From the distance, they seem to be steeper than they actually are.

How Is A Bluff Formed?

How a bluff is formed in geography is a question that has no clear answer. It all depends on the environment that the bluff was formed in and other factors like how deep it is and how much erosion takes place.

When a bluff is created naturally, it forms by the force of wind and water along with the effect of gravity on the earth’s surface. This natural process mainly happens in steep places where there are high elevation changes.

As the slope becomes too steep for the water or wind to erode it, it builds up and forms a bluff.

Bluffs are also formed by the slow movement of glaciers, ice sheets, and permafrost. Glaciers push large amounts of rock off of mountainside through grinding and crushing – this produces large boulders that act as rubble dams blocking the flow of streams.

How To Identify A Bluff In Geography?

Bluffs are natural formations that can be found near water and mountain ranges. They take many forms and typically look like a hill reaching the sky or a mound of rock.

There are many ways to identify a bluff. A bluff is usually steep enough to have a significant decline or incline on both sides of the top.

The bluffs are not just steep but have uneven, sharp sawtooth edges that provide cover for any assailant. The bluff is also made up of large stones that have become cemented together over time and are covered with moss and vegetation, which further provides cover from above.

Bluff is not higher than its surroundings but it grants an advantage to those who use it as cover from above due to the uneven, sharp edges.

Bluffs are also characterized by their lack of vegetation and the presence of large rock formations jutting out from them.

In order to identify a bluff, you need to look at the shape and size. The bluffs should be steep, irregularly shaped.

What Is A Bluff On A Lake Or Beach?

A bluff is a shoreline that plunges abruptly into the water, as seen in some lakes and rivers. In order to prevent erosion from the water, the land behind a bluff is often protected by planting shrubs and trees along the steep slope of the bank.

A bluff can be created naturally or artificially through human efforts such as earth-moving projects, filling of river beds, building dams, or installing rock protections.

Cliff vs Bluff [What Is A Bluff In Geography]

Here are some of the differences between a bluff and a cliff:

Cliff

A cliff is a sharp change in elevation with little or no horizontal level between two points of different elevations. A cliff face is usually vertical or nearly so but can also be almost flat at low elevations.

Such features are typically found in mountainous terrain and may be formed either by erosion or by other types of geological activity.

Cliffs can be considered natural features that stabilize a slope, preventing further erosion and landslides from occurring on the mountainside, but they have also been used for building retaining walls and even as places to live.

Bluff

A bluff is a high point of land that appears to be very steep, but it is actually not.

Bluffs are generally found on the side of a mountain or hill, but sometimes they are found on level ground or even on the seashore.

Bluffs are defined by their steepness, meaning the difference in elevation between the highest point on top of the bluff and its base.

Conclusion: What Is A Bluff In Geography

When you are talking about geography, bluff can be a natural feature, a geological formation, or an archaeological site. These things that are difficult to see from one perspective are easy to spot from another perspective.

Bluff is the name given to a low-lying area of land that is surrounded by steep cliffs, steep slopes, or water. It’s the place you hide in when you don’t want to be seen.

Additional Information

A bluff is a type of broad, rounded cliff. Most bluffs border a river, beach, or other coastal area.

Bluffs may form along a river where it meanders, or curves from side to side. River currents on the outside of the curve erode, or wear away, the lower part of a river bank. No longer supported, the upper part of the bank breaks off, leaving the high wall of a bluff. The 150-meter (500-foot) Great River Bluffs in the U.S. state of Minnesota, for example, were carved by the meanderings of the mighty Mississippi River.

Erosion also produces bluffs along the wider floodplain of a river. Over thousands of years, a meandering river gradually shifts from side to side across its floodplain. Where the meanders, or loops, of the river reach valley walls, the water may carve bluffs. In fact, a “bluff line” defines the outer limits of a river’s floodplain, and is often another name for valley wall. A floodplain’s bluff lines may be steep and narrow, or they may be wide and gentle.

Coastal bluffs are formed through a combination of erosion from wind, sea spray, and crashing waves. These bluffs are often more rugged than their inland counterparts, and are more vulnerable to major erosion. Coastal bluffs, especially those in the Puget Sound region of the U.S. state of Washington, are sometimes called feeder bluffs. The constant erosion of feeder bluffs supplies (feeds) sediment to the beaches and seashore downstream below.

Another sort of coastal bluff is the beach ridge. Beach ridges are formed entirely by waves lapping onshore, pushing sand and sediment up and away from the body of water. Beach ridges run parallel to the shoreline and are often associated with sand dunes. The Indiana Dunes, for example, are extensions of beach ridges formed by the waters of Lake Michigan. At this national lakeshore, tiny bluffs give way to larger dunes, and the ecosystem eventually creates the ideal conditions for an oak forest through the process of plant succession.

Like many types of cliffs, bluffs provide important information about how Earth developed. Scotts Bluff, for instance, rises more than 1,400 meters (4,600 feet) above the North Platte River in the U.S. state of Nebraska. The exposed rock of this national monument allows geologists to peer more than 30 million years into North America’s past. Rock formations at Scotts Bluff preserve the history of ancient volcanic activity nearby, as well as the fossilized presence of prehistoric North American rhinos, tapirs, and even camels.

Life on the Bluff

The summits of many bluffs are bare, rocky outcroppings. However, the harsh environment of bluffs are often vital ecosystems. Tiny organisms called lichen often colonize rocky bluffs, providing vital nutrients for many insects and birds.

Hardy grasses and shrubs can also take root on rocky bluffs. The shallow roots of these plants slow erosion of the bluff, even helping to secure valuable topsoil in some places.

Bluffs provide an ideal nesting spot for fishing birds such as cormorants and kingfishers. Cormorants build their nests on the bare ground of bluffs, bringing sticks and seaweed for construction. Cormorant colonies can grow so large that they take over the entire bluff. Kingfishers don’t nest on top the bluff, but dig a burrow directly in it. They prefer burrows on bluffs with little vegetation, as root systems get in the way of digging.

Bluffs are even home to endangered species. The El Segundo blue butterfly (Euphilotes battoides allyni), for example, is found only in a small bluff ecosystem near the giant Los Angeles International Airport in Southern California.