| A | B |
|---|
| virus | a tiny particle that can reproduce only inside the cells of living things |
| bacteria | tiny, one-celled organisms, some of which can cause diseases |
| cell | the basic unit of a living organism |
| cell membrane | a thin layer that makes up the outside of the cell and controls what enters and leaves it |
| nucleus | the cell part that controls the cell's activities; the center of an atom, where protons and neutrons are located |
| cell wall | a stiff outer layer that helps keep plant cells firm |
| cytoplasm | jellylike material that fillls most of a cell |
| chloroplast | the green cell part in plant cells that traps and uses light energy |
| classify | to arrange in groups using a system |
| kingdom | that largest group into which an organism is classified |
| genus | a group of similar species |
| species | a group of organisms of only one kind that can interbreed in nature |
| invertebrate | an animal that has no backbone |
| vertebrate | an animal with a backbone |
| mammal | an animal that has hair or fur and feeds its young with milk produced by the mother |
| vascular plant | a plant with long tubes inside that carry food and water to all the parts of the plant |
| egg cell | a cell that can join with a sperm cell to form a new individual |
| sperm cell | a cell that can join with an egg cell to form a new indivdual |
