| A | B |
|---|
| niche | how an organism survives, including its habitat, how it obtains food and shelter, and how it avoids danger |
| habitat | the place in which an organism lives |
| population | all the organisms in an ecosystem that belong to the same species |
| community | all the populations in an ecosystem |
| ecosystem | all the organisms living in an area and the nonliving features of their environment |
| biosphere | the part of Earth that supports life, including the top portion of Earth's crust, all the waters that cover Earth's surface, and the surrounding atmosphere |
| limiting factor | anything that restricts the number of individuals in a population |
| carrying capacity | the largest number of individuals of one species that an ecosystem can support over time |
| ecology | the study of interactions that occur among organisms and their environment |
| producers | organisms that use an outside energy source, such as the Sun, to make energy-rich molecules |
| consumers | organisms that cannot make their own energy-rich molecules |
| symbiosis | any close relationship between species |
| mutualism | a symbiotic relationship in which both species benefit |
| commensalism | a symbiotic relationship in which one organism benefits and the other is not affected |
| parasitism | a symbiotic relationship in which one organism benefits but the other is harmed |
