Definitions / Explanation : Homology & Adaptive radiation or divergent evolution
It is the similarity between organs of different animals based on common ancestry or common embryonic origin and built on the same fundamental pattern but perform varied functions and have different appearance e.g. Seal flipper and forelimbs of birds, bat, horse and human look different, perform different functions but exhibit same structural plan.
It represents evolution of new forms in several directions from the common ancestral type (divergence).
Definitions / Explanation : Analogous organs & Vestigial or rudimentary organs
$A$ : During evolution pouched mammals of Australia survived.
$R$ : Due to lack of competition from any other mammal due to continental drift
Assertion : Natural selection is the outcome of difference in survival and reproduction among individuals that show variation in one or more traits.
Reason : Adaptive forms of a given trait tend to become more common; less adaptive ones become less common or disappear.
Complete fossil of whose among the following is found
Contribution of scientist : Hugo de Vries, Hardy - Weinberg and Ernest Haeckel.