What is the primary focus of population genetics?

The primary focus of population genetics is the study of genetic variation within a population. This field examines how genes and their variations (alleles) are distributed among individuals in a population, as well as how these distributions change over time due to evolutionary processes such as natural selection, mutation, gene flow, and genetic drift. Understanding genetic variation is crucial because it provides insights into the adaptability of populations, their potential for evolution, and their responses to environmental changes.

In contrast, other options delve into broader aspects of biology. The processes of evolution in individual species pertain more to species-level changes rather than the genetic composition of populations. The effects of environmental factors on population size focus on ecology rather than genetic variation. Lastly, interactions between different species in an ecosystem are related to community ecology and biodiversity, which lie outside the primary scope of population genetics. Thus, the correct answer highlights the fundamental connection between genetics and population dynamics.