Differential reproductive success
Natural selection occurs when inherited differences mean that individuals do not all reproduce with equal success. In a particular environment, an allele can give its possessor a better chance of surviving long enough to reproduce.
This produces differential reproductive success. Individuals with favourable genetic variants contribute proportionally more offspring to the following generation, allowing those alleles to be inherited more often.
Mutation and advantageous alleles
- A random mutation can create a new allele.
- Many mutations either reduce an organism's chances of success or make no apparent difference.
- In certain environmental conditions, however, a new allele may give its possessor an advantage.
- That advantage can increase the individual's likelihood of surviving and reproducing.
- When reproduction occurs, the favourable allele may be passed to offspring.
Natural selection therefore links inherited genetic variation to differences in reproductive success.