Final answer:
Reduction in the genetic diversity of populations of organisms can be caused by genetic drift, genetic bottleneck, and natural selection.
Step-by-step explanation:
Reduction in the genetic diversity of populations of organisms can be caused by several processes.
1. Genetic drift: This is the random change in allele frequencies in a population due to chance events. It is more likely to occur in small populations, where chance events can have a larger impact. For example, if a small population of organisms is affected by a natural disaster, the survivors may have a limited genetic diversity.
2. Genetic bottleneck: This occurs when a population undergoes a drastic reduction in size, resulting in a loss of genetic diversity. This can happen due to factors like habitat loss, disease outbreaks, or human activities. For example, if a large forest is cleared for development, the population of organisms living in that forest may experience a genetic bottleneck.
3. Natural selection: This is the process by which certain traits or alleles become more common in a population over time, based on their fitness in a given environment. If certain alleles are advantageous, they will be selected for and become more prevalent in the population, reducing genetic diversity. For example, if a population of organisms is exposed to a new predator, individuals with certain traits that make them less visible to the predator may have a higher chance of survival and reproduction.