1. Study of the effects of atmospheric conditions (weather) on living organisms.
2. That branch of ecology that deals with the effects on living organisms of the extra-organic aspects of the physical environment; such as, temperature, humidity, barometric pressure, rate of air flow, and air ionization.

It involves not only natural atmosphere but also artificially created atmospheres; such as, those to be found in buildings and shelters, and in closed ecological systems; for example, satellites and submarines.