Ecology investigates the relationships living organisms have with each other and with their physical environment. Evolution is a unifying theme of biology that is inextricably linked to ecology. It investigates how mutation, selection, and other factors shape organisms and their interactions with the environment. Microbiologists and plant biologists within the department study ecology and evolution at molecular, ecosystem, and planetary levels, investigating events that occur over a short period of time or over millions of years. Faculty expertise covers a broad range of fields that include ecosystem dynamics, climate change, conservation, taxonomy, systematics, physiology, and ethnobotany.