Variations in a population are essential for the survival of a population because if all the population are the same then the population won't survive if they come aross something they're vulnerable to.

With more variety there is more likelyhood for survival of the population because only a part of it could be vulnerable to something.

Homologous structures

structures with common evolutionary origin; can be similar in arrangement function or both; provides evidence of evolution from a common ancestor

Convergent Evolution

evolution in which distantly related organisms evolve and develop similar traits; occurs when unrelated species occupy similar environments.

Divergent evolution

evolution in which species that were once similar to an ancestral species diverge; occurs when populations change as they adapt to different environmental conditions; eventually resulting in a new species.