| A | B |
|---|
| organism | a living thing |
| cell | basic unit of structure and function in an organism |
| unicellular | made of a single cell |
| multicellualr | consisting of many cells |
| stimulus | change in an organism’s surroundings that causes the organism to react |
| response | action or change in behavior that occurs as a result of a stimulus |
| development | process of change that occurs during an organism’s life to produce a more complex organism |
| spontaneous generation | mistaken idea that living things arise from nonliving sources |
| autotroph | organism that makes its own food |
| heterotroph | organism that cannot make its own food |
| homeostasis | maintenance of stable internal conditions |
| classification | process of grouping things based on their similarities |
| taxonomy | scientific study of how living things are classified |
| binomal nomenclature | system for naming organisms in which each organism is given a unique, two-part scientific name indicating its genus and species |
| genus | classification grouping that consists of a number of similar, closely related species |
| species | group of similar organisms that can mate with each other and produce offspring that can also mate and reproduce |
| prokaryote | organism whose cells do not contain a nucleus |
| nucleus | dense area in a eukaryotic cell that contains nucleic acids, the chemical instructions that direct the cell’s activities |
| eukaryote | organism whose cells contain a nucleus |
| microscope | instrument that makes small objects look larger |
| cell theory | widely accepted explanation of the relationship between cells and living things |
| organelles | tiny cell structure that carries out a specific function within the cell |
| cell wall | rigid layer of nonliving material that surrounds the cells of plants and some other organisms |
| cell membrane | cell structure that controls which substances can enter or leave the cell |
| cytoplasm | region between the cell membrane and the nucleus; in organisms without a nucleus, the region located inside the cell membrane |
| endoplasmic reticulum | cell structure that forms a maze of passageways in which proteins and other materials are carried from one part of the cell to another |
| ribosome | small grain—like structure in the cytoplasm of a cell where proteins are made |
| vacuole | sac inside a cell that acts as a storage area |
| chloroplast | structure in the cells of plants and some other organisms that captures energy from sunlight and uses it to produce food |
| Golgi body | structure in a cell that receives proteins and other newly formed materials from the endoplasmic reticulum, packages them, and distributes them to other parts of the cell |
| lysosome | small, round cell structure containing chemicals that break down large food particles into smaller ones |
| mitochondria | rod-shaped cell structures that convert energy in food molecules to energy the cell can use to carry out its functions |
