'Prototheria' means the egg laying mammals. Spiny anteater and duck-billed platypus are egg laying mammals.

Cetacea includes highly specialised group of aquatic mammals such as dolphins, whales and porpoises.

Probscidea includes the mammals with trunk. For example, elephants.

Mammals with higher brain like humans, monkeys are included in order Primata.

Order Ungulata includes hoofed mammals like camel, pigs, sheep, cows, etc.

Spleen lies behind the stomach and stores lymph and white blood cells.

The purification of blood takes place in the lungs.

Mammals are warm blooded mammals.

Some animals like deer provide medicines to us.

Shrew helps to destroy harmful insects.

Whale provides oil and bone.

Uterus is a female reproductive organ where development of embryo takes place.

Pig belongs to the order Ungulate. However, Roendtia includes rodents like mice, squirrels and guinea pigs.

Orangutan is known as 'man of the forests'. It measures about 1¼ meters in height and feeds largely on fruits.

Flesh eating mammals come under the order Carnivora. Hippopotamus comes under the order Ungulate as it is a hoofed mammal.

'Metatheria' includes the pouch bearing mammals such as kangaroo, opossum, koala and bear. They bear young ones, which are in immature state. The further development of young ones takes place in the abdominal pouch of the female known as marsupium.

Chiroptera includes the flying mammals like bats. The forelimbs of these mammals have elongated digits, which are supported by thin membranous skin.

In mammals, reproduction is internal as the ovum is fertilized in the oviducts.

'Eutheria' means placental mammals. The term 'eutheria' is derived from the fact that the embryo grows inside the uterus and is supplied with nutrients through placenta.