About birds

NOTE Even aquatic reptiles return to the land to lay eggs.the male has a copulatory organ, the penis,evolven to place sperms into the body of the female during mating the other characteristics of a reptile are: it is coid blooded. it has a well developed tongue which can be protruded and retracted quickly. its jaws have teeth of the same kind embedded in sockets.it usually has paired fore and hindlimbs, each with five toes ending in claws. It has inner and middle ears.it has an incopletely developed four chambered heart. Aves this class includes all types of birds, both fightless and flying birds.A bird has the following features : it is a warm blooded (homoiothermic) vertebrate, i.e.it is able to keep its body temperature is higher than that of the surroudings. it head, neck and trunk are covered with feathers ; its hindlegs , with scales. its forelimbs are modified into wings for flying .its hindlegs have feet, each with four toes ending in claws. its jaws are drawn out to form a toothless beak for feeding. its skeleton is rigid and the bones have air sacs. Only the vertebrae in the neck are flexible. these features are adaptations for flight. it has good eye sight. it also has only inner and middle ears . it has a four chambered heart. Fertilization is internal. The female lays large eggs with hard shells and large yolks. The egg hatch into young which are often helpless and are looked after by the parent birds. We can easily recognize birds because of their unique covering of feathers .since feathers are actually modified scales,biologists believe that birds have evolved from reptiles.to fur ther support this ,birds have scale(a reptilian feature)on their legs,while ancestral birds has teeth similar to those of reptiles. Mammalia we belong to this group, which is made up of the most advanced animals. The main characteristics of a mammal are as follows :it is warm blooded. its skin has sweat and sebaceous gland and a covering of hairs. it has different types of teeth, with each type carrying out a specific function . it has external ears called pinnae . its body cavity is separated into two by a muscular sheet called a diapheagm.the up per thoracic cavity contain the lungs and the heart while the lower abdominal cavity contains the alimentary canal,the kidneys and the reproductive organs.


Aaa