To determine which of the given scenarios will decrease the genetic variation of a population, we need to understand what genetic variation is and how it can be affected.
Genetic variation refers to the diversity in genetic characteristics within a population. It is caused by several factors, including mutations, gene flow, genetic drift, and natural selection. It is important because it allows populations to adapt and evolve in response to environmental changes.
Now, let's examine the scenarios to determine which one would decrease the genetic variation of a population:
1. Increase in mutation rate: Mutations are the primary source of genetic variation, as they introduce new alleles into a population. Therefore, an increase in the mutation rate would actually increase genetic variation rather than decrease it. So, this scenario does not decrease genetic variation.
2. Decrease in gene flow: Gene flow refers to the transfer of genes between populations. It occurs when individuals move, mate, or exchange genetic material between populations. Gene flow facilitates the mixing of different gene pools, thereby increasing genetic variation. A decrease in gene flow, such as limited migration, would restrict the transfer of genes and reduce genetic variation. Thus, this scenario could decrease genetic variation.
3. Increase in genetic drift: Genetic drift refers to random changes in allele frequencies in a population due to chance events. It is more prevalent in smaller populations and can lead to the loss of certain alleles and a decrease in genetic variation. Therefore, an increase in genetic drift, such as population bottlenecks or founder effects, would decrease genetic variation.
4. Increase in natural selection: Natural selection is the process by which individuals with advantageous traits have higher chances of survival and reproduction. This process can lead to the elimination of less favorable alleles, reducing genetic variation. Therefore, an increase in natural selection intensity could potentially decrease genetic variation.
Based on the analysis above, scenarios 2 (decrease in gene flow), 3 (increase in genetic drift), and 4 (increase in natural selection) could all decrease the genetic variation of a population. Scenario 1 (increase in mutation rate) would actually increase genetic variation.