aboiotic Non-living factor in an ecosystem, such as moisture, temperature, wind, sunlight, soil, and minerals. autotroph organism that obtains its energy from abiotic sources, such as sunlight or inorganic chemicals. biogeochemical cycle movement of a chemical through the biological and geological, or living and nonliving, parts of an ecosystem. biomass total dry mass of all organisms in a given area. biome Regional or global community of organisms characterized by the climate conditions and plant communites that thrive there. bioremediation A process by which humans use living things to break down pollutants. biosphere all organisms and the part of Earth where they exist. biotic living things such as, plants, animals, fungi, and bacteria. community Collection of all the different populations that live in one area. detritivore organism that eats dead organic matter. ecology Study of the interactions among living things and their surroundings. ecosystem Collection of organisms and nonliving things, such as climate, soil, water, and rocks, in an area. food chain model that links organisms by their feeding relationships. food web model that shows the complex network of feeding relationships within an ecosystem. habitat combined biotic and abiotic factors found in the area where an organism lives. heterotroph organism that obtains its energy and nutrients by consuming other organisms. nitrogen fixation process by which certain types of bacteria convert gaseous nitrogen into compounds. population all of the individuals of a species that live in the same area. population dispersion way in which individuals of a population are spread out over an area or volume. predation process by which one organism hunts and kills another organism for food. symbiosis ecological relationship between members of at least two different species that live in direct contact with one another. trophic level level of nourishment in a food chain..