| Term | Definition |
| adaptation | inherited characteristic that increases an organism's chance of survival |
| endangered species | a species whose numbers are so small that the species is at risk of extinction |
| extinction | no longer in existence |
| habitat | Place where an Organism lives |
| niche | (ecology) the status of an organism within its environment and community (affecting its survival as a species) |
| pollution | Release of harmful materials into the environment |
| predator | animal that hunts and eats other animals |
| prey | animal hunted or caught for food |
| symbiosis | the relation between two different species of organisms that are interdependent |
| threatened species | a species that could become endangered in the near future |
| abiotic | any nonliving component of an environment |
| biotic | the living organisms in an ecosystem |
| biosphere | part of Earth in which life exists including land, water, and air or atmosphere |
| ecology | the branch of biology concerned with the relations between organisms and their environment |
| carnivore | Meat eater |
| herbivore | any animal that feeds chiefly on grass and other plants |
| omnivore | organism that obtains energy by eating both plants and animals |
| parasitism | the relation between two different kinds of organisms in which one receives benefits from the other by causing damage to it (usually not fatal damage) |
| commensalism | the relation between two different kinds of organisms when one receives benefits from the other without damaging it |
| population | a group of organisms of the same species populating a given area |
| fossil | the remains (or an impression) of a plant or animal that existed in a past geological age and that has been excavated from the soil |
| ice age | any period of time during which glaciers covered a large part of the earth's surface |
| producer | an organism that makes its own food |
| mutualism | the relation between two different species of organisms that are interdependent |
| consumer | an organism that obtains energy by feeding on other organisms |