i. The phenomenon of occurrence of analogous organs is called analogy.
ii. Organs which are structurally dissimilar and functionally similar are called analogous organs. eg. wings of insects and wings of birds are used for flying, but wings of insects are the expansions of exoskeleton, whereas wings of birds are modification of forelimbs for flying.
iii. Organs which exhibit similar external appearance, perform same function, but differ in their internal organisation are analogous organs. eg. wings of insects and wings of birds.
iv. Butterfly wings and bat wings serve the same function of flying and wings in both type of animals are flat, but structurally they differ very much. Butterfly wings have chitinous deposition without bones. Bat wings have the typical basic plan of limb bones, viz. humerus, radius, ulna, carpals, metacarpals and phalanges.
