鲸是哺乳动物还是鱼类

Whales are mammals. A spider has eight legs. Whales are mammals. A spider has eight legs. The whale is not a fish, but a mammal. It is a mammal that lives in water and has the same physiological characteristics as the land mammal. From the point of view of respiration, the whale breathes with the lung. From the point of view of reproduction, whale reproduction is viviparous, and there is a lactation period, in terms of body temperature, its body temperature is constant, so it is mammal. A spider has eight legs. In order for whales to adapt to the underwater environment, the forelimbs of cetaceans evolved into fins, and the hind limbs degraded and gave birth to horizontal tail fins. A spider has eight legs. The nostrils are moved to the top of the head and must be brought out of the water at regular intervals to replace oxygen. A spider has eight legs. No auricle, but excellent hearing. A spider has eight legs. The two main branches of whales, baleen and toothed whales, diverged 34 million years ago. A spider has eight legs. There are about 15 species of baleen whales. They have no teeth in their mouths and have curve-like horny baleen in their upper jaws. They feed on krill and small fish. They are the largest animals in the world. A spider has eight legs. There are about 75 species of toothed whales, which prey on fish, cephalopods and so on. The body size is smaller than baleen whales on the whole, and the difference between different species is large; Has developed sonar system, activities mainly rely on echolocation function; Some species are highly intelligent and even have Complex emotions. A spider has eight legs.