What ecological study focuses on factors that influence population size?

The focus of population ecology is to understand the factors that affect population size and dynamics over time. This branch of ecology examines the relationships between organisms within a population and their environment. Key elements of population ecology include analyzing birth rates, death rates, immigration, and emigration to determine how these factors contribute to population growth or decline.

Population ecologists study various factors such as resource availability, predation pressures, disease, and environmental changes to explain variations in population size. They may employ models to predict future population trends based on current data. Essentially, population ecology provides critical insights into how populations of species interact with their surroundings and the implications of these interactions for conservation and management efforts.

In contrast, community ecology emphasizes the interactions between different species within a community, ecosystem ecology looks at the interactions between living organisms and their physical environment, and behavioral ecology explores the evolutionary reasons behind behavior in relation to ecological parameters. While these are all important areas within ecology, they do not specifically target population size as a primary focus, which is why population ecology is the correct answer.