| A | B |
|---|
| ecology | the study of how organisms interact with one another and with their environment |
| species | a group of individuals that interbreed and produce fertile offspring |
| population | the members of a species that live in the same area. |
| community | all of the population in a particular area |
| ecosystem | all living things and their physical environments within a particular area. |
| biosphere | the Earth and all of its organisms and environments |
| biotic factors | any part of an ecosystem that is living or used to be living |
| abiotic factors | any part of an ecosystem that has never been living |
| habitat | the specific environment in which an organism lives |
| resource | anything an organism needs; includes nutrition, shelter, mates, and breeding sites. |
| population size | the number of individual organisms present in a population at any given time |
| population density | the number of individuals in a population per unit of area |
| population distribution | how organisms are arranged within an area; sometimes called population dispersion. |
| age structure | the relative number of organisms of each age within a population; also called age distribution. |
| age structure diagram | a chart that shows the age distribution of a population; also called age pyramid. |
| sex ration | the proportion of males to females in a population |
| survivorship curve | a graph showing the likelihood of survival within a group or population by age. |
| immigration | the movement of individuals to a given area. |
| emigration | the movement of individuals away from a given area. |
| migration | the seasonal movement of organisms into and out of an area. |
| exponential growth | the pattern of population growth in which a population increases by a fixed percentage each year. |
| limiting factor | a characteristic of the environment that restricts population growth. |
| carrying capacity | the largest population a given environment can support. |
| logistic growth | the pattern of population growth in which exponential growth is slowed and finally stopped by limiting factors. |
| density-dependent factor | a limiting factor whose influence changes with population density; includes competition, predation, and disease. |
| density-independent factor | a limiting factor whose influence is not affected by population density; includes catastrophic events. |
| biotic potential | the growth rate of a population under ideal conditions. |
