Fitness in evolutionary terms refers to an organism's ability to survive and reproduce successfully in its environment, passing on its genes to the next generation.

The theory of evolution by natural selection posits that random mutations, competition for resources, and environmental changes collectively drive the adaptation and diversification of species.

Natural selection is the process by which organisms with advantageous traits are more likely to survive and reproduce, passing on those traits to their offspring.

Genetic drift is the gradual change in the genetic composition of a population over time, due to random fluctuations in gene frequencies.

Adaptation is the process by which organisms develop new traits or characteristics in response to changes in their environment, increasing their chances of survival and reproduction.

Gene flow is the process by which genetic material is randomly transferred from one organism to another, typically through mating or migration.

Sexual selection is the process by which the genetic makeup of a population changes due to non-random mating patterns, typically driven by mate choice preferences.

Hybridization is the process by which the genetic makeup of a population changes due to the introduction of new genetic material through interbreeding between different species or populations.

Assortative mating is the process by which organisms with similar traits tend to mate with each other, leading to the accumulation of certain traits within a population.

Disassortative mating is the process by which organisms with different traits tend to mate with each other, leading to the mixing of genetic material and increased genetic diversity.

The bottleneck effect is the process by which the genetic makeup of a population changes due to the loss of genetic diversity, typically caused by a drastic reduction in population size.

The founder effect is the process by which the genetic makeup of a population changes due to the expansion of a small group of individuals, typically leading to a reduction in genetic diversity.

Adaptive radiation is the process by which organisms evolve to occupy different niches in the same environment, often leading to the diversification of species.

Convergent evolution is the process by which organisms from different lineages evolve to have similar traits in response to similar environmental pressures, leading to analogous structures.

Divergent evolution is the process by which organisms from different lineages evolve to have different traits in response to different environmental pressures, leading to the diversification of species.