Final answer:
Evolutionary change is influenced by genetic drift, gene flow, mutation, nonrandom mating, and environmental variances, in addition to natural selection and sexual selection. These forces contribute to changes in allele frequencies in a population's gene pool and can lead to evolution over time.
Step-by-step explanation:
Apart from natural selection and sexual selection, there are several other causes of evolutionary change, including:
- Genetic drift - Random changes in allele frequencies that can have a significant effect on small populations.
- Gene flow - The movement of alleles into or out of a population due to the migration of individuals or gametes (like pollen).
- Mutation - Random changes in DNA that can introduce new alleles into a population's gene pool.
- Nonrandom mating - Mating that does not occur randomly, which can influence which alleles are passed onto offspring.
- Environmental variances - Differences in environments that can impact the survival and reproductive success of individuals with certain traits.
These mechanisms can result in changes in a population's allele frequencies, leading to evolutionary change that is not necessarily adaptive.