Final answer:
Differential reproduction of genotypes, influenced by varying fitness levels, is the process of natural selection, which is a key component of evolution. Organisms with genotypes better adapted to their environment tend to reproduce more successfully, leading to evolution of the species. This process is affected by mechanisms like mutations, which introduce new genetic variations, and sexual reproduction, which mixes alleles to create diverse offspring.
Step-by-step explanation:
The differential reproduction of genotypes, resulting from their variable fitness, is a fundamental concept in evolution known as natural selection. In essence, organisms with genotypes that are more suited to their environment tend to survive and reproduce at higher rates than those with less adaptive genotypes. This concept is illustrated through various mechanisms such as mutations and sexual reproduction. Mutations can introduce new alleles that might affect an organism's phenotype positively, negatively, or neutrally in terms of fitness. Moreover, sexual reproduction contributes to genetic diversity as it leads to unique combinations of alleles in the offspring.
An excellent example of this dynamic is Moree's study on Drosophila melanogaster, where the relative fitness of a recessive allele for black eye color varied with the population density. This indicates that the environment plays a key role in determining fitness. In changing environments, those with genetic variation that confers advantageous traits are more likely to survive. If such changes are consistent, these traits become more common in the population over generations, illustrating the principle of differential survival and reproduction.