Environment, all of the external factors affecting an organism. These  factors may be other  living  organisms  (biotic factors)  or nonliving variables (abiotic factors), such as temperature, rainfall, day   length,   wind,   and   ocean   currents.   The   interactions  of organisms  with  biotic  and  abiotic  factors  form  an  ecosystem. Even  minute  changes  in  any  one   factor in an ecosystem   can influence  whether  or   not  a  particular  plant  or  animal  species will be successful in its environment.