Variation, mutation and selection
Variation is the differences between individuals. Continuous variation has a range of values (height, mass) and is affected by many genes and the environment; discontinuous variation falls into distinct groups (blood group) and is mainly genetic. Mutations are random changes in DNA that create new alleles. In natural selection, individuals with features better suited to the environment survive, reproduce and pass on their alleles, so populations change over time: evolution. Artificial selection (selective breeding) is when humans choose which individuals breed.
≈ 40 min