Ecology

2. the process, performed by certain bacteria found in the nodules of leguminous plants, that make the atmospheric nitrogen available for use in organisms.
8. The flow of chemical elements and compounds between living organisms and the physical environment.
9. the amount of living matter in a given habitat, expressed either as the weight of organisms per unit area or as the volume of organisms per unit volume of habitat.
10. the substance or substances of which any physical object consists or is composed.
11. an environmental factor that tends to limit population size.
12. a system, or a group of interconnected elements, formed by the interaction of a community of organisms with their environment.
13. substance that living organisms obtain from the environment to carry out life processes and sustain life.
15. the branch of biology dealing with the relations and interactions between organisms and their environment, including other organisms.
16. a complex biotic community characterized by distinctive plant and animal species and maintained under the climatic conditions of the region, especially such a community that has developed to climax.
17. the ecosystem comprising the entire earth and the living organisms that inhabit it.
18. the process of removing nitrogen compounds from the soil back into nitrogen gas.
19. the living together of two dissimilar organisms, as in mutualism, commensalism, amensalism, or parasitism.

1. the natural environment of an organism; place that is natural for the life and growth of an organism.
3. the progressive replacement of one community by another until a climax community is established.
4. the position or function of an organism in a community of plants and animals.
5. an organism’s ability to survive biotic and abiotic factors.
6. an assemblage of interacting populations occupying a given area.
7. factor a nonliving condition or thing, as climate or habitat, that influences or affects an ecosystem and the organisms in it.
14. all the individuals of one species in a given area.
16. factor a living thing, as an animal or plant, that influences or affects an ecosystem.