Explain Use and Disuse theory.

Explanation

(i)Lamarck.s Use and Disuse theory states that if an organ is used contantly,the organ develops well and gets strengthened.
(ii)When an organ is not used for a long time, it gradually degenerates.
(iii)The ancestors of Giraffe were provided with short neck and short forelimbs.
(iv)Due to shortage of grass, they were forced to feed on leaves from trees.
The continous stretching of their neck and forelimmbs resulted in the development of long neck and long forelimbs which is an example for constant use of an organ.
(v)The degenerated wing of Kiwi is an example for organ of disuse.