What is the primary focus of research involving population dynamics?

The primary focus of research involving population dynamics is the analysis of changes in population size and density. Population dynamics examines how and why populations of organisms change over time, including factors that influence their growth, decline, and fluctuations. This field encompasses various elements such as birth rates, death rates, immigration, and emigration, which all contribute to the understanding of species' population structures and how they interact with their environments.

By investigating these changes, researchers can identify trends that might indicate issues like resource scarcity, environmental changes, or the impacts of human activities on ecosystems. This understanding is crucial in fields such as conservation biology, wildlife management, and ecology, where knowing how populations behave under various conditions can guide efforts to maintain biodiversity and ecosystem balance.

In contrast, the other options, while related to ecological studies, focus on different aspects. The study of climate change effects on habitats deals with how environmental shifts affect living conditions for species. The examination of species interactions looks at relationships between different organisms, such as predation or competition, rather than on population metrics directly. The exploration of soil composition pertains to biogeochemical processes and land use, which are important but do not specifically address population dynamics.