Question

What are the characteristic features of mammals?

Answer 1

Mammals are a group of vertebrate animals. They belong to class Mammalia. The organisms of this class are taken to be the most developed among animals. mammals live in water and on land. In order to live in different environments, mammals have developed certain adaptive features. The most commonly known and advanced of the mammals are human beings.

Complete answer:
Mammals are believed to have evolved from the Synapsid clade. The organisms of this clade diverged into two groups – one containing the birds and reptiles and the other the mammals. The predicted diversion of mammals took place around the Carboniferous period, around 200-300 million years ago. The features that distinguish mammals from the rest of the Synapsids are listed below:
-Presence of mammary glands. The mammary glands are present in both males and females. However, they are only active in females and produce milk to feed the offspring.
-Presence of malleus, incus and stapes in the ear.
-Body is covered with fur or hair.
-Presence of neopallium or neocortex in the brain. This region is responsible for cognitive skills, language, sensory perceptions, etc.
-Mammals generally give birth to their offspring as opposed to the egg laying nature of the avian and reptilian relatives.
-Presence of sebaceous and oil glands on the skin.
-The heart of mammals is typically four chambered, consisting of two atria and two ventricles.
-The Red Blood Cell or RBC(s) of mammals lack nuclei.
-The mammals have an external ear, also known as the pinna.
-The mammals have two sets of teeth, that is they are Diphyodont.
-Presence of twelve pairs of cranial nerves.
-Respiration takes place through lungs.
-Mammals are capable of regulating their body temperature, that is they are warm blooded animals.

Note: The mammals are a higher group of vertebrate animals that belong to class Mammalia. They are known to have diversified from the birds and reptiles around 200 to 300 million years ago. The presence of mammary glands is a characteristic feature of mammals. They are also known to give birth of their offspring, rather than to lay eggs. The most commonly known mammals are tigers, lions, dogs, wolves, monkeys, chimps, etc, apart from human beings.