What does physiology study?

Physiology is a branch of biology that focuses on the functions and mechanisms of living organisms. It examines how the various systems within a body operate, how they interact with each other, and how they respond to changes in their environment. This includes studying processes such as respiration, circulation, digestion, and neural activity, among others. By understanding these processes, physiology reveals the complex biological functions that sustain life.

The other options represent different areas of biological study. For instance, studying cell structures falls under cell biology or cytology, while genetic variations pertain to genetics and heredity. Environmental interactions would involve ecology, which looks at how organisms interact with their environment and each other. While all these areas contribute to our understanding of life, physiology specifically targets the functional aspects of living things.