Population ecology is a branch of biology that investigates how different organisms of the same species interact with each other and their environment. It is concerned with understanding the factors that determine population size, density, distribution, and changes over time. Scientists analyze the interactions between individuals within a population, such as competition for resources like food, water, and shelter. They also study how populations are affected by external factors, like predation, disease, and environmental conditions. By studying population ecology, scientists can gain insights into the mechanisms that influence population growth, decline, and stability.