A population that has been isolated, especially a smaller one, could have a high level of homozygosity and therefore not a lot of genetic variation. Gene flow between such populations can increase the level of heterozygosity, and therefore up genetic variation.
It is needed by all living things and every living cell to carry out life processes, such as breaking down and building up molecules, and transporting many molecules across cell membranes. The form of energy that living things need for these processes is chemical energy, and it comes from food.
A derived trait is a trait that the current organism has, but the previous one did not have.An ancestral trait is a trait that you, and your ancestors had.A vestigial structure is a structure that had some sort of use in your ancestor, but none in your current body
