Today is

By: Ikedi Ani-okoye.

Mammals introduction

Of all the classes of animal life, mammals are considered the most advanced and probably the most popular class. Dogs and cats are mammals, squirrels and rabbits in our backyards are mammals as well. Horses, sheep, baboons, giraffes and elephants are mammals. For that matter, we human beings are mammals too.

What is a Mammal?

Mammals are warm-blooded,vertebrate animals characterized by the presence of sweat glands, including milk producing sweat glands , and by the presence of: hair, three middle ear bones used in hearing, and a neocortex region in the brain. Also all mammals, other than the monotremes, give birth to live young instead of laying eggs. Most mammals also possess specialized teeth and utilize a placenta in the ontogeny.

Monotreme Mammals

Monotremes are egg-laying mammals. They are called monotremes because they have only one posterior opening, the cloaca into which the rectum and urinogenital sinus both open and through which gametes, urine and faeces all pass to the outside. The eggs are fertilised internally and laid in a nest.

The young are suckled from mammary glands, which do not have nipples, but open individually over a large area of the ventral surface of the female. monotremes lack external ears. The two families of extanct monotremes - the platypuses and echidnas - have decidely different appearances and life styles. They occur only in Australasia.

Mammals and dinosaurs

Early mammals shared the planet with the dinosaurs. Some of the primitive mammals (which included early marsupials and insectivores) that lived during the latter part of the Cretaceous period (144mya-65mya) survived the global catastrophe that brought about the extinction of the dinosaurs. Some of the surviving marsupials gave rise to placental mammals, which include many of the mammals familiar to us today. The extinction of the dinosaurs marked the end of the Age of Reptiles and the dawn of the Age of Mammals.

CONCLUSION

Mammals, especially humans, have an instinctive need for social and emotional bonding. There's a biological reason for this: the part of our brain known as the limbic system, which humans, mammals, and birds all have, while reptiles, amphibians, and simpler creatures do not. This is why humans, mammals, and birds all instinctively nurture their young, while many other creatures basically give birth and then slither away without a backward glance.