Question

Flight has evolved independently three times in the animal kingdom. Compare and contrast the three different evolved forms of flight in the animal kingdom. Discuss the groups they evolved in and the specific structural differences and similarities.

Answer 1

Flight has evolved independently three times in animal kingdom ,that is found in imsects ,birds and pterosaraus without having any single ancestors.

Flight is of two type that is unpowered and powered ,

In unpowered mode of flight , animal uses aerodynamics forces exerted on the body due to the wind or falling through the wind . Whereas in powered flight , the use of muscular power is done to generate aerodynamic forces to maintain a steady level flight.

Powered flight is often seen in animals ,first in instects ,then in pterosaurs ,then in birds.

In insects ,flight is able to do through direct action of a muscle on each wing. One set of wing is attached just inside the base of the wing and the other set is attached slightly outside the wing base. When the first set of flight muscles contract ,the wings move upward and the second set of muscles produces the downward stroke of the wing. The two sets of wings work in alternative contractions to move the wings up and down.

Pterosaurs flew with the help of their forelimbs.Their long,tapering wings evolve from the same body parts as of our arms. The arm and hand bones are evolved for flying in pterosaurs ,these bones have lengthened and the bones of one finger which is equivalent to our ring finger became extraordinary long.

Birds can perform two types of flight known as soaring or gliding flight and flapping flight. Birds fly in a same way as aircraft which involves lift and drag forces. Lift force is produced by the action of air flow on the wing ,which is an airfoil. The air provides a net upward force on the wing due to the airfoil ,while the movement of air is directed downward.

Drag is the opposite force to the direction of motion and hence is the source of energy loss in flight.

The birds wing which is the forelimb are the reason of flight . Each wing has a central vane to hit the wind which is composed of humerus ,ulna and radius. The flight feathers are responsible for the wings airfoil shape and other flight feathers behind the carpal joint on the ulna are known as secondaries. The remaining feathers are known as coverts which are of 3 types.

The streamline of the bird's body and wings helps the bird to fly.