Populations evolve, not individuals. A population is a group of individuals belonging to the same species, occupying the same given area, and showing certain morphological, physiological, and behavioral traits in common. A population exhibits immense variation in its individual members, all of which by definition are of the same species but vary in the details of their shared characteristics.
Gene mutations create new alleles.
Crossing over at meiosis leads to new combinations of alleles. Independent assortment in meiosis mixes paternal and maternal chromosomes. 1817- 15 colonists 2. 1. beach mouse populations on Atlantic and Gulf Coasts 2. reproduce rapidly until hurricane storm surge drowns most members of populations creating a bottleneck. 3. survivors which begin reproducing again are not as genetically diverse as those living in the area before the hurricane.