Biology, the study of life, historically was divided into zoology, the scientific study of animals, and botany, the scientific study of plants, which in the past included the bacteria, algae, lichens, fungi. Botany today is more often called plant biology or sometimes plant science.
Botanists may specialize in a subject matter field like ecology or genetics or else study all aspects of one group of plants, (and are then called bryologists if they study mosses, for example, or pteridologists if they study ferns). The plant scientists in applied fields like forestry or horticulture rarely call themselves botanists, but they often study the same processes and structures as do botanists. Microbiologists investigate microorganisms such as bacteria and may specialize in such aspects as microbial ecology. Molecular biologists are interested in the structure and function of biological macromolecules and study such processes as the biochemical aspects of genetics while plant physiologists analyze metabolic processes such as photosynthesis.