| Question | Answer |
| obligate symbionts | A symbiotic relationship between two organisms in which neither by themselves can exist without the other. |
| genetic drift | Changes in the frequency of a gene in a population as a result of chance rather than of mutation, selection, or migration. Can be caused by an accident that leaves only a small population alive to reproduce. |
| symbiont | Each partner in symbiosis. |
| biological diversity | Used loosely to mean the variety of life on Earth, but scientifically typically has 3 components: 1)genetic diversity; 2)species diversity; 3)habitat or ecosystem diversity. See the text for additional information. |
| biological evolution | The change in inherited characteristics of a population from generation to generation, which can result in new species. |
| ecological niche | The general concept is that the niche is a species' "profession" - what it does to make a living. The term is also used to refer to a set of environmental conditions within which a species is able to persist. |
| habitat | Where an individual, population, or species exists or can exist. For example, the habitat of the Joshua tree is the Mojave Desert of Southern California. |
| mutation | Stated most simply, a chemical change in a DNA molecule. It means that the DNA carries a different message than it did before, and this change can affect the expressed characteristics when cells or individual organisms reproduce. |
| species | A group of organisms that can interbreed and produce fertile offspring. |
| gene | A single unit of genetic information comprised of a complex segment of the four DNA base-pair compounds. |
| natural selection | A process by which organisms whose biological characteristics better fit them to the environment are represented by more decendants in future generation than those whose characteristics are less fit for the environment. |
| competitive exclusion principle | The idea that 2 populations of different species with exactly the same requirements cannot persist indefinitely in the same habitat - one will always win out and the other will become extinct. |
| symbiosis | An interaction between individuals of 2 different species that benifits both. For example, lichens contain an alga and a fungus that require each other to persist. |
| migration | The movement of an individual, population, or species from one habitat to another or more simply from one geographic area to another. |
