# Introduction to Evolutionary Biology

Evolution is a change in the gene pool of a population over time. A
gene is a hereditary unit that can be passed on unaltered for many
generations. The gene pool is the set of all genes in a species or
population.

Populations evolve. In order to understand evolution, it is necessary
to view populations as a collection of individuals, each harboring a
different set of traits. Individual organisms do not evolve, they
retain the same genes throughout their life.