What branch of biology is concerned with the functions of life?

The branch of biology that is focused on the functions of life is physiology. Physiology studies the various functions and mechanisms of living organisms, including how cells, tissues, organs, and systems operate and interact to sustain life. It encompasses a wide range of topics such as the processes of respiration, digestion, circulation, and other vital functions that are essential for an organism's survival and overall well-being.

In contrast, ecology examines the relationships between organisms and their environment, looking at ecosystems, biodiversity, and how living beings interact with their surroundings. Entomology is the study of insects specifically, focusing on their behavior, ecology, and physiology, but it does not encompass all functions of life across organisms. Genetics deals with heredity and the variation of traits in organisms, primarily focusing on genes and their roles in inheritance, rather than the overarching functions of life itself. Therefore, physiology is the most appropriate answer when discussing the functions critical to life's processes.