Explain how fitness can change the allele frequency of a population. PLZ no link
The Correct Answer and Explanation is:
Fitness, in an evolutionary context, refers to the ability of an organism to survive, reproduce, and pass on its genes to the next generation. This concept is central to understanding how natural selection drives changes in allele frequencies within a population over time.
Allele frequency is the proportion of a specific allele (variant of a gene) in a population. When individuals with higher fitness — meaning they are better adapted to their environment — are more likely to survive and reproduce, their alleles become more common in the population. Over successive generations, these advantageous alleles increase in frequency, while less beneficial or harmful alleles decrease.
There are several key mechanisms through which fitness impacts allele frequency:
- Natural Selection: Natural selection favors individuals with traits that enhance survival and reproduction in their specific environment. For example, if a certain allele provides resistance to a disease, individuals with that allele are more likely to survive and reproduce. Over time, the allele frequency of the disease-resistant gene will increase, because those without the allele are less likely to pass on their genes.
- Directional Selection: This occurs when environmental pressures favor one extreme phenotype, driving an increase in the frequency of alleles that produce that phenotype. For instance, in a population of moths, darker-colored moths might have a fitness advantage in polluted environments because they are less visible to predators. As a result, the allele for dark coloration increases in frequency.
- Stabilizing Selection: This type of selection favors average individuals in a population and reduces genetic diversity. Alleles that produce extreme traits may decrease in frequency, while those that produce intermediate traits become more common.
In summary, fitness influences allele frequency by determining which individuals are more likely to reproduce and pass their alleles to future generations. Over time, this leads to an increase in favorable alleles and a decrease in those that reduce fitness.