Wednesday, June 29, 2011

EXTINCT ANIMALS

Extinct and Endangered Animals:

The extinction of species has always been a natural part of evolution. The fossil record shows that since life originated about four billion years ago the vast majority of species that have existed are now extinct. Extinct species outnumber living ones by a factor of perhaps a thousand to one.

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sciencegnus
Scientists have identified five extinction events in Earth's history, with some so severe that more than 90 percent of all life forms were killed off. The last and most famous extinction was the Cretaceous-Tertiary event some 63 million years ago that killed off the dinosaurs and allowed the rise of mammals. It is thought to have been caused by an asteroid hitting Earth.

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Dinosaur
Today we are in the middle of a sixth extinction events that began about 50,000 years ago but is now accelerating in an alarming speed! This extinction event is not a natural event, but is caused directly or indirectly by humans.
Most recent extinctions extinctions have been associated with European expansion in the 15th and 16th century. However, in some parts of the world some species are known to have become extinct before the arrival of the Europeans. For example, the Polynesians who colonised the Hawaiian Island in the 4th, 5th, and 6th centuries may have been responsible for the loss of around 50 of the 100 or so species of endemic land birds in the period between their arrival and that of the Europeans.


Pictures Of some Extinct/Endangered Animals
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African Elephant
  The African elephant is the largest living land animal and weighs up to 5,400 kg. It inhabits the Savannah, brush, forest, river valleys, and semi-desert regions of Africa south of the Sahara Desert. Besides its greater size, it differs from the asian elephant in having larger ears and tusks, a sloping forehead, and two “fingers” at the tip of its trunk, compared to only one in the Asian species.

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Green Turtle
Female green turtles return to the same beaches regularly and in great numbers to lay their eggs. Throughout history these turtles have been an important source of food to local human populations and sea voyagers. The green turtle was once common in the warm oceans of the world, but has become increasingly scarce in areas where it is commercially exploited. It is still common, however, in Hawaii, but now rarely nests in North America, although feeding areas in Florida still have fairly large populations. The green turtle can also be found around Australia.

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Bald Eagle

This majestic bird is found across all of southern Canada, but is commonest on the Pacific coast. The Bald eagle also ranges in Alaska and the rest of the United States. The adult can be distinguished by its white head and neck which it takes about four years to attain. Adult males have a body length of 75 to 85 cm and a wingspan of 180 to 213 cm. Females are slightly larger.

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Dodo
 Mauritius, an island in the Indian Ocean, was the only home of the dodo, a large,flightless bird that weighed up to 14 kg and was very good to eat. Dodos were an easy-to-catch source of food for sailors and settlers.
Having developed in isolation, the dodo easily fell victim to this new pressure. In addition, forest clearing destroyed the bird’s habitat, and introduced pigs, goats, cats, rats, and monkeys became competitors as well as predators. 


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African Wild Dog
Although similar in appearance to hyenas, African wild dogs are nevertheless true wild canidae. They are a mixture of black, yellow, and white in such a wide variety of patterns that no two individuals look exactly alike. African wild dogs are widely distributed across the African plains but they do not live in jungle areas.
They are social animals, living in packs of usually from 2 to 45 individuals. A hierarchy exists within the pack, but the animals are so friendly to one another that the pecking order is hard to determine. The young and the infirm are given special privileges within the pack.
African wild dogs use their sense of sight, not smell, to find their prey. They pay no attention to wind direction and they do not use cover when approaching their prey. They can run up to 55 km/h for several kilometres. In eastern Africa, they mostly hunt Thomson’s gazelles, but they will also attack calves, warthogs, zebras, impalas, and the young of large antelopes such as the gnu.



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Wild Yak

Throughout history, the domesticated yak of central Asia has provided Tibetan herders with wool, leather, meat, milk, and cheese. It is a beast of burden and its dung is used as fuel and fertilizer. There are many of them. The larger wild yak, however, decimated by hunting, is an endangered species.Once widely distributed in the high valleys and plateaus of Tibet and the adjoining mountain country, the wild yak now survives in scattered, isolated herds in the most remote, inhospitable areas. Although officially protected from hunting and commercial trade, its future may depend on suitable reserves with good pastures and efficient protection. 


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Mountain Gorilla
This largest of the great apes inhabits a number of isolated areas on the forested mountain slopes of eastern Zaire and parts of Uganda and Rwanda. Its population is estimated at approximately 400. Although much of the animal’s range is within national parks and reserves, human's growing needs for farming and grazing lands have reduced these areas. These disruptions may also force other animals, such as elephant and buffalo, into a reduced habitat where they compete with the gorilla for the same foods.
Listed as an endangered species the mountain gorilla has some protection in a ban among most zoos against the acquisition of specimens and in restrictive controls against international trade.  




















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