Explanations:The classification of animals into mammals and non-mammals is based on a set of defining characteristics. Mammals are a class of vertebrates that share several key features, including the presence of mammary glands, which produce milk to feed their young, and the ability to regulate their body temperature internally (endothermy). Mammals are typically warm-blooded and give birth to live young, although there are exceptions like the platypus and echidna, which lay eggs but still possess mammary glands and other mammalian traits.
Sharks, on the other hand, are not classified as mammals. They are fish, which are cold-blooded and do not have mammary glands. Sharks reproduce by laying eggs or giving birth to live young, but they do not produce milk to feed their offspring. Instead, they rely on external sources of nutrition for their young, which is a key difference from mammals.
Whales, despite living in water, are classified as mammals. They are warm-blooded, have mammary glands, and nurse their young with milk. Whales are part of the mammalian class and are adapted to an aquatic lifestyle, but they retain the essential mammalian characteristics.
Bears are also classified as mammals. They are warm-blooded, have mammary glands, and nurse their young with milk. Bears are terrestrial mammals and are part of the mammalian class, sharing the same defining characteristics as other mammals.
Bats are another example of mammals. They are warm-blooded, have mammary glands, and nurse their young with milk. Bats are unique among mammals as they are the only mammals capable of sustained flight, but they still possess all the essential mammalian traits.
In summary, the classification of animals into mammals and non-mammals is based on a set of defining characteristics, including the presence of mammary glands, warm-bloodedness, and the ability to regulate body temperature internally. Sharks do not possess these characteristics and are therefore not classified as mammals, while whales, bears, and bats are all classified as mammals due to their shared traits.