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НазваThe animals of Eurasia (реферат)
РозділІноземна мова, реферати англійською, німецькою
ФорматWord Doc
Тип документуРеферат
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Eurasia is the largest land mass on earth, stretching halfway around
the globe from the British Isles to the Pacific Ocean, and from the
Bering Sea south to the tip of Malaysia, an area of 54 million sq km (21
million:sq -л»ХА few of its animal species, especially those in the
north, are closely related to, and in some instances are the same as,
those of North America.

Relatively recently, as earth time is measured, Eurasia was linked to
America by a land bridge which spanned what is now the Bering Straits.
This causeway existed for thousands of years during the Ice Ages, when
much of the earth's water was locked up in glaciers, thus lowering sea
level. Animals crossed back and forth between the two continents on the
land bridge, and the first human settlers in America probably arrived
via this route.

About ten thousand years ago, the latest in a series of ice ages came to
an end. The ice melted; the seas rose, and the Bering land bridge was
submerged. Animal species which had wandered west into Eurasia or east
to America were isolated from their native homelands. But because ten
thousand years is a mere eye wink in evolutionary timekeeping, very few
changes have had time to take place in these exiles. For example, the
largest member of the deer family lives in the taiga of both Eurasia and
America. In Eurasia it is called an elk, in America, a moose. But it is
one and the same animal. This is also true of another deer, the caribou,
or reindeer. The former is a wild animal of America; the latter has been
domesticated for centuries by the Lapps of northern Europe.

The Bering land bridge was probably responsible for the survival of at
least one species — the horse. This animal originated in the western
hemisphere, where it developed from a tiny, three-toed creature, to the
form very much like the one we know today. During the Ice Ages, it
migrated across the land bridge into Asia, where it thrived. In America
the horse became extinct and didn't reappear here until the Spaniards
brought it back as a domesticated animal in the 16th century.

The Spanish horses, as are all domestic breeds, were descendants of the
wild horses which migrated from America. That original breed still
exists. It is called Przewalski's horse, named for the naturalist who
first brought specimens to Europe from the grasslands of Mongolia. This
is the only true wild horse left in the world. All other so-called
"wild" horses are feral animals, that is, horses descended from domestic
animals which escaped from or were released by their owners.
Przewalski's horses once existed in large herds, but human intrusion
into their habitat pushed them farther and farther back into a harsh
environment where even these tough animals could not survive.

They were last seen in the wilderness in 1967. Fortunately breeding
groups existed in zoos and reserves. Captive propagation brought the
population up to about 700 by 1985, and four dozen Przewalski's horses
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