Apart from human beings, cow, buffalo, sheep, goat, etc. come under the category of mammals. Mammals are those living beings whose females produce milk to suckle their young. They are warm-blooded and have well-developed brains. They give birth to live Youngs and feed them with their own milk. They breathe air through lungs and their bodies are covered with hair. Do you know how the female mammals produce milk?
Milk in the female mammals is produced by ‘mammary glands’ which are located in the breasts. They are bag shaped and big in size. Shortly before the birth of her young, hormonal changes in the mother results in increased development of the mammary glands. They produce large drops of fat which when mixed with fluids present in the breasts become milk. Corpus luteum of the ovary also produces a hormone which helps in the process of milk production. Most of female mammals have teats or nipples from which the young can suck milk.
At present there are about 4400 living species of mammals grouped into 19 orders and about 120 families. They, of course, differ from one another in their bodies, shapes, sizes and habits. Most of them live on land but some live in water and air also. For example, the whale is a mammal which lives in water. And the bat is also a mammal which flies in the air. They exist in different climatic conditions – hot, cold, dry or humid. Most mammals give birth to less than 10 young a year. Humans usually have only one baby at a time.