Evolution as a change in allele frequency. Genetics explains sources of variety such as camouflage or mimicry, within species, coming from gene shuffling and mutations, and these beneficial genetic variations are passed down through natural selection.
How does natural selection affect allele frequency?
Natural selection can either be directional (pushing one direction towards greater fitness), stabilizing, (removing variety to increase populations fitness), or disruptive (separating towards two species with greater fitness in their own niche). This can be graphed and measured with respect to allele frequency.
What is speciation?
Species are a population that can interbreed with one another. If this population experiences reproductive isolation (geographical, behavioral, temporal) and the mechanisms for evolution are all present, then the population can split into multiple different species.