CBSE Class 10 Science 2017 · Paper 31/2/C · Question 4

Analogous organs are organs that have a different basic structure and a different origin but perform a similar function (and may look alike) - for example, the wings of an insect and the wings of a bird or a bat. The wing of a butterfly and the wing of a bat cannot be considered homologous organs because homologous organs must have the same basic structure and origin, and these two do not. Reason: the bat’s wing is a modified forelimb, a fold of skin stretched between the bones of the arm and the long fingers, whereas the butterfly’s wing is a thin membrane growing out of the body wall, supported by veins and with no bones. They only perform the same function, flying, so they are analogous organs.