| A | B |
|---|
| oxygen | a part of the air that is needed by most plants and animals to live |
| organism | a living thing that carries out five basic life functions on its own |
| cell | the smallest unit of living matter |
| tissue | a group of similar cells that work together to carry out a job |
| organ | a group of tissues that work together to do a certain job |
| organ system | a group of organs that work together to carry on life functions |
| kingdom | the largest group into which an organism can be classified |
| trait | a characteristic of a living thing |
| genus | a group made up of two or more very similar species |
| species | the smallest group into which an organism is classified |
| fossil | any evidence of an organism that lived in the past |
| embryo | a developing organism that results from fertilization |
| extinct | said of an organism no longer alive on Earth |
| ecosystem | the study of how living and nonliving things interact |
| community | the living part of an ecosystem |
| population | one type of organism living in an area |
| habitat | the home of an organism |
| producer | an organism, such as a plant, that makes food |
| consumer | any organism that eats the food producers make |
| decomposer | an organism that breaks down wastes and the remains of other organisms |
| food chain | the set of steps in which organisms get the food they need to survive |
| food web | the pattern that shows how food chains are related |
| drought | a long period of time with little or no precipitation |
| overpopulation | a depletion of resources that occur when too many of at least one kind of living thing inhabits an ecosystem |
| pollution | the addinfg of harmful substances to the water, air, or land |
| acid rain | harmful moisture that falls to Earth after being mixed with wastes from burned fossil fuels |
