Which of the following is true regarding the relationship between environmental factors and population sizes?

The relationship between environmental factors and population sizes is largely driven by how changes in those environmental conditions impact resources, habitat, and the overall ecosystem. When environmental conditions change—whether through natural events, climate shifts, or human activities—it can lead to fluctuations in the availability of food, water, and suitable living conditions.

For example, a drought can decrease water availability, impacting not just one species but the entire food web, leading to declines in certain populations. Conversely, favorable conditions, such as a period of abundant rainfall or a lack of predators, can lead to population booms. These fluctuations are a natural response of populations trying to adapt to their changing environments. Thus, the statement that changes in environmental conditions can lead to fluctuations in population sizes is accurate; it highlights the dynamic interplay between ecosystems and the organisms that inhabit them.

The other options fail to capture this complexity. Some suggest that populations are completely unaffected by environmental changes, or that stability in environments leads to population fluctuations, which contradicts the observed ecological patterns. Similarly, claiming all populations respond the same to environmental factors overlooks the diversity of species and their varied adaptations.