Evolution & Biodiversity

Mutations create diversity and meiosis and sexual reproduction mix that diversity, but at the end of the day evolution is the process which selects biodiversity.

Some characteristics can be heritable (e. g. eye color) while others aren‘t (muscles hypertrophy is linked to sport practice). Heritable characteristics are transmitted from the parents to their child via meiosis and sexual reproduction.
Some of those characteristics, which appeared randomly trough mutations, can be an advantage in terms of survival or reproduction for the individuals who have it, and their proportion will thus increase in the population with time. That’s natural selection.
Other characteristics are neutral and their proportion will randomly vary through time, some being erased faster with a smaller population (genetic drift).

Homologous structures support evolution and reveal a common ancestral trait. Analogous structures show that evolution can select different solutions to face an environmental contingency.

Homologous structures are structures that can be found in different species that have the same evolutive origin. The easiest hypothesis is that the common ancestor for both species already had this structure and it was then adapted differently through time in both branches leading to difference in shape or possibility. Animals‘ pentadactyl limb is a very good example of a homologous structure that is shared by flyers (e. g. bats), swimmers (dolphins) or walkers (humans).
Analogous structures are structures that come from different evolutive origins, which fulfil the same function. Those structures have appeared more than once in the past in different ancestral species. For example, the wings of a bat (pentadactyl limb) don’t have the same origin as the wings of a butterfly.

Evolution leads to diversification and eventually, speciation.

Evolution selects characteristics in populations. Populations are individuals of the same species living together at the same time and place. But different scenarios can lead to the formation of a new species from that population, for example:

1. Geographic isolation from the rest of the species can lead to divergent evolution ;
2. The appearance of new characteristics in the population can lead to reproductive isolation of a part of this population ;
3. The migration of a part of a population in a new environment can select different characteristics as well.