Origin and Evolution of Life — BIOLOGY STD 12 Science — Question

1. The structural similarities between the homologous organs indicate that they have a common ancestry.
2. Different homologous organs indicate divergent evolution or adaptive radiation.
3. Homologous organs help in tracing the phylogenetic relationships.
4. Homologous organs are those organs which are structurally similar but functionally dissimilar.

E.g.
(i) Forelimbs of frog, lizard, bird, bat, whale and man are homologous to each other. All the limbs are morphologically similar in construction such as similar limb bones but are dissimilar in function. Frog limbs are meant for hopping, lizard limbs help in crawling, birds and bats fly with the . help of forelimbs while whale uses it for swimming and man for handling the objects.

(ii) Vertebrate heart and brain. & In plants, thorns of Bougainvillea and tendrils of Cucurbita represent homology.