Study of living things and their vital processes. An extremely broad subject, biology is divided into branches. The current approach is based on the levels of biological organization involved (e.g., molecules, cells, individuals, populations) and on the specific topic under investigation (e.g., structure and function, growth and development). According to this scheme, biology's main subdivisions include morphology, physiology, taxonomy, embryology, genetics, and ecology, each of which can be further subdivided. Alternatively, biology can be divided into fields especially concerned with one type of living thing; for example, botany (plants), zoology (animals), ornithology (birds), entomology (insects), mycology (fungi), microbiology (microorganisms), and bacteriology (bacteria). See also biochemistry; molecular biology.