Question

Which of the following animals are mammals?
Elephant, snake, hen, cow, lizard, monkey, peacock, cockroach, whale.

Answer 1

Hint: Animals which are placed underclass Mammalia are referred to as mammals. They are found in every habitat like oceans, deserts, rivers etc. They come under the category of vertebrates which are divided into amphibians, reptiles, Pisces, birds and mammals. This classification is done on an anatomical and physiological basis.

Complete answer:
The characteristic features of mammals that distinguish them from other organisms are:
- Mammals are the most advanced and dominant form of organisms found on Earth.
- They are warm-blooded animals which means they can maintain a constant body temperature and most of the mammals are viviparous i.e., who give birth to their younger ones, but some animals like kangaroo lay eggs.
- Another striking feature of these organisms is the presence of mammary glands which are used to feed their offspring. They also possess sebaceous glands and sudoriferous glands.
- Their heart is four-chambered and their brain is well organised and divided into cerebellum cerebrum and medulla.
- Respiration is through the lungs with the presence of the most advanced diaphragm and the nervous system is also well organised with twelve pair of cranial nerves.

Among the following animal’s elephant, snake, hen, cow, lizard, monkey, peacock, cockroach, whale only elephant, cow, monkey and whales come under the category mammals. Whales, penguins and porpoises come under order cetaceans, which were considered early to be amphibious. These are the only mammals that spend their entire lifetime in water. Snakes and lizards come under the class of reptiles
Cockroach belongs to the class of insects. Peacock and hen belong to the class of birds

Note: Mammals are also classified into three subclasses on the basis of their reproduction. They are;
- Eutheria: Animals under this category give birth to young ones. The offspring develops inside the mother’s foetus until they are matured. This happens in animals like elephants.
- Metatheria: Animals give birth to immature ones and they stay in their mother’s pouch till maturity is attained. For example, kangaroo
- Prototheria: They are egg laying mammals like platypus.