| A | B |
|---|
| ecosystem | All the living and nonliving things that interact in an area. |
| habitat | The place where an organism lives and that provides the things it needs. |
| biotic factor | A living part of an ecosystem. |
| abiotic factor | A nonliving part of an ecosystem. |
| photosynthesis | The process in which organisms use water along with carbon dioxide and sunlight to make food. |
| species | A group of organisms that are similar and reproduce to produce fertile offspring. |
| population | All the members of one species in a particular area. |
| community | All the different populations that live together in an area. |
| ecology | The study of how living things interact with each other and their environment. |
| population density | The number of individuals in a specific area. |
| estimate | An approximation of a number based on reasonable assumptions. |
| birth rate | The number of births in a population in a certain amount of time. |
| death rate | The number of deaths in an area in a certain amount of time. |
| immigration | Moving into a population. |
| emigration | Leaving a population. |
| limiting factor | An environmental factor that prevents a population from increasing. |
| carrying capacity | The largest population that an area can support. |
| natural selection | Process by which individuals that are better adapted to the environment are more likely to survive and reproduce than others. |
| adaptation | The behaviors and physical characteristics of species that allow them to live successfully in their environments. |
| niche | An organism's particular role in an ecosystem, or how it makes its living. |
| competition | The struggle between organisms for the limited resources in a habitat. |
| predation | An interaction in which one organism kills and eats another. |
| predator | The organism that does the killing in predation. |
| prey | An organism that is killed in predation. |
| symbiosis | A close relationship between species that benefits at least one of the species. |
| mutualism | A relationship between two species in which both species benefit. |
| commensalism | A relationship between two species in which one species benefits and the other is neither helped nor harmed. |
| parasitism | A relationship in which one organism lives on or inside another and harms it. |
| parasite | The organism that benefits by living on or inside a host in parasitism. |
| host | The animal that a parasite lives in or on in parasitism. |
