| A | B |
|---|
| Archaea | One of two prokaryotic domains of life, the other being Bacteria. |
| Bacteria | One of two prokaryotic domains of life, the other being Archaea. |
| biology | The scientific study of life. |
| biosphere | The entire portion of Earth inhabited by life; the sum of all the planet's ecosystems. |
| cell | A basic unit of living matter separated from its environment by a plasma membrane; the fundamental structural unit of life. |
| community | An assemblage of all the organisms living together and potentially interacting in a particular area. |
| consumer | An organism that obtains its food by eating plants or by eating animals that have eaten plants. |
| controlled experiment | A component of the process of science whereby a scientist carries out two parallel tests, an experimental test and a control test. The experimental test differs from the control by one factor, the variable. |
| domain | A taxonomic category above the kingdom level. The three domains of life are Archaea, Bacteria, and Eukarya. |
| ecosystem | All the organisms in a given area, along with the nonliving (abiotic) factors with which they interact; a biological community and its physical environment. |
| emergent properties | New properties that emerge with each step upward in the hierarchy of life, owing to the arrangement and interactions of parts as complexity increases. |
| Eukarya | The domain that includes all eukaryotic organisms. |
| eukaryotic cell | A type of cell that has a membrane-enclosed nucleus and other membrane-enclosed organelles. All organisms except bacteria and archaea are composed of eukaryotic cells. |
| evolution | Descent with modification; the idea that living species are descendants of ancestral species that were different from present-day ones; also the genetic changes in a population over generations. |
| gene | A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses). Most of the genes of a eukaryote are located in its chromosomal DNA; a few are carried by the DNA of mitochondria and chloroplasts. |
| hypothesis | A tentative explanation a scientist proposes for a specific phenomenon that has been observed. |
| molecule | A group of two or more atoms held together by covalent bonds. |
| natural selection | A process in which organisms with certain inherited characteristics are more likely to survive and reproduce than are organisms with other characteristics. |
| organ | A structure consisting of several tissues adapted as a group to perform specific functions. |
| organ system | A group of organs that work together in performing vital body functions. |
| organelle | A membrane-enclosed structure with a specialized function within a cell. |
| organism | An individual living thing, such as a bacterium, fungus, protist, plant, or animal. |
| population | A group of individuals belonging to one species and living in the same geographic area. |
| producer | An organism that makes organic food molecules from CO2, H2O, and other inorganic raw materials: a plant, alga, or autotrophic bacterium. |
| prokaryotic cell | A type of cell lacking a membrane-enclosed nucleus and other membrane-enclosed organelles; found only in the domains Bacteria and Archaea. |
| species | A group whose members possess similar anatomical characteristics and have the ability to interbreed and produce viable, fertile offspring. See biological species concept. |
| systems biology | An approach to studying biology that aims to model the dynamic behavior of whole biological systems. |
| technology | The practical application of scientific knowledge. |
| theory | A widely accepted explanatory idea that is broad in scope and supported by a large body of evidence. |
| tissue | An integrated group of cells with a common function, structure, or both. |
