Encyclopedia Britannica Illustrated Science Library 2009 11 – Mammals

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Encyclopedia Britannica Illustrated
Science Library 2009 11 – Mammals
Edition 2009
pages 56


Encyclopedia Britannica Illustrated
Science Library 2009 11 – Mammals

.Mammals began to dominate the Earth about 65 million years ago
Without a doubt, modern humans are the most successful mammals
they occupy all the Earth’s habitats! Their domestic coexistence with
other species began barely 10,000 years BC, when human culture
transitioned from a world of nomadic hunters and gatherers to a society
based on agriculture. At that time, humans began to benefit from
the meat and milk products of small mammals and to use large
animals for labor. The first animals to be domesticated were
sheep (about 9000 BC) in the Middle East. Pigs, cows, goats, and
dogs followed. However, the great majority of mammal species
continue, even today, to live in the wild. There are 5,416 known
mammal species distributed over different land and aquatic
environments. Despite the characteristics that make them part of the
same class, their diversity is such that the smallest of them, the
,shrew, may weigh only one tenth of an ounce (3 g), and the largest
the blue whale, can reach 160 tons. But their diversity is also
evident in their adaptation to different environments. There are
mammals that run and others that glide some fly, and others
jump, swim, or crawl. Most aquatic mammals have suppressed
the development of hair or fur, replacing it with thick layers of
fat. The rigors of low temperatures have made some animals
such as polar bears, dormice, and certain bats exceptions to the
vital law of homeothermy, as they spend the winter sunk in deep
sleep to save energy. WALES Land of green meadows and gentle
hills, Wales is famous the world over for the quality of its wool
production. Seals, dolphins, bats, and chimpanzees all have upper
limbs with similar bones, but the environmental niche they occupy
has made seals develop flippers, dolphins fins, bats wings, and
chimpanzees arms. Thus from the polar tundra to the dense
tropical jungle, through the deep oceans and high mountain
lakes, the whole Earth has been populated by thousands of
mammal species. But this marvelous animal world has been
disturbed by its most numerous species humankind. Indiscriminate
,hunting, illegal trade, deforestation, urbanization
massive tourism, and pollution have left more than a thousand
. species (many of them mammals) endangered or vulnerable
However, science allows us to understand nature’s many
wonders, and it can help us respect the world’s ecological
balance. In this book, which includes dazzling photographs
and illustrations, we invite you to discover many details of
mammals’ lives: their life cycles, their social lives, their special
features, and their characteristics, from those of the greatest
.friend of them all, the dog, to the mysterious and solitary platypus