Whales , the biggest animals of the world, belong to family of mammals. They are from group of Cetacea. To this group belong also dolphins. They are probably the strangest mammals , which we know. Their body reminds a fish. Instead of front legs, they have fins and another pair of legs we don´t see. Instead of fish the whales have warm blood , they breathe air and their cubs are born living. Instead of that they have no problem with living in the water, it is possible that they have earthliving ancestors. They have very good ears and special ability utilize oxygen 2-3 times better than other mammals. We can see them in the seas all over the world. Some of them are living in tropical rivers. Today many of them are in danger of extinction.
Dolphins are aquatic mammals which are closely related to whales and porpoises. There are almost forty species of dolphin in seventeen genera. They vary in size from 1.2 metres and 40 kilograms (Maui's Dolphin), up to 9.5 m and ten tonnes (the Orca). They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating fish and squid. The family Delphinidae is the largest in the Cetacea, and relatively recent: dolphins evolved about ten million years ago, during the Miocene. Dolphins are considered to be amongst the most intelligent of animals and their often friendly appearance and seemingly playful attitude have made them popular in human culture.
Ďaľšie referáty z kategórie
Whales and dolphins - Esey
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