| A | B |
|---|
| compare | To point out how things are alike and how they are different. |
| contrast | To show differences. |
| virus | A tiny particle that can reproduce only inside the cells of living things. |
| cell | The basic unit of a living organism. |
| nucleus | The cell part that controls the cell's activities. |
| cell membrane | A thin layer that makes up the ouside of the cell and controls what enters and leaves it. |
| cytoplasm | A jellylike material that fills most of a cell |
| cell wall | A stiff outer layer that helps keep the plant cell firm. |
| chloroplast | The green cell part in the plant cells that traps and uses light energy. |
| classify | To arrange in groups using a system. |
| kingdom | The 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 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 individual. |
