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Unit 7
AP Biology Unit 7 Vocabulary
| Term | Definition |
|---|---|
| Evolution | Descent with modification; the idea that living species are descendants of ancestral species that were different from the present-day ones. |
| Evolution Fitness | quantitative representation of natural and sexual selection within evolutionary biology. It can be defined either with respect to a genotype or to a phenotype in a given environment. |
| Natural Selection | When nature (environment) selects which traits will become more frequent in a population by conferring a survival advantage to individuals with certain traits. |
| Selective Pressure | Selective pressures are environmental factors that cause some individuals to have greater fitness than others. |
| Adaptive Radiation | Period of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological roles in their communities. |
| Biological Species Concept | Definition of a species as a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring, but do not produce viable, fertile offspring with members of other such groups. |
| Divergent Evolution | The accumulation of differences between closely related populations within a species, leading to speciation. |
| Gradualism | A theory that assumes large morphological changes in organisms occur via a number of smaller step over a number of years. The evolution of new species by gradual accumulation of small genetic changes over long periods of time. |
| Punctuated Equilibrium | In the fossil record, long periods of apparent stasis, in which a species undergoes little or no morphological change, interrupted by relatively brief periods of sudden change. |
| Reproductive Isolation | The existence of biological factors (barriers) that impede members of two species from producing viable, fertile offspring. |
| Speciation | An evolutionary process in which one species splits into two or more species. |
| Ecosystems | All the organisms in a given area as well as the abiotic factors with which they interact; one or more communities and the physical environment around them. |
| Extinction | A downward population spiral in which inbreeding and genetic drift combine to cause a small population to shrink and, unless the spiral is reversed, become extinct. |
| Niche | The role an organism plays in a community. A species' niche encompasses both the physical and environmental conditions it requires (like temperature or terrain) and the interactions it has with other species (like predation or competition). |
| Species Diversity | The number and relative abundance of species in a biological community. |
| RNA World Hypothesis | Life on Earth began with a simple RNA molecule that could copy itself without help from other molecules. DNA, RNA, and proteins are central to life on Earth. |
| Convergent Evolution | The evolution of similar features in independent evolutionary lineages. |
| Bottleneck Effect | When a population has a big reduction in its genetic variation, it is called the bottleneck effect. |
| Founder Effect | The founder effect is when a small number of individuals, the founders, leave a population and start a new one. |
| Genetic Drift | Genetic drift happens when there are random changes in the allele frequency of a population. |
| Mutation | Random changes in DNA that create new alleles. |
| Population | A group of individuals of the same species that live in the same area and interbreed, producing fertile offspring. |
| Hardy-Weinberg Equilibrium | The principle that frequencies of alleles and genotypes in a population remain constant from generations to generation, provided that only Mendelian segregation and recombination of alleles are at work. |
| Migration | A regular, long-distance change in location. |
| Null Hypothesis | An assumption or proposition where an observed difference between two samples of a statistical population is purely accidental and not due to systematic causes. |
| Fossil | A preserved remnant or impression of an organism that lived in the past. |
| Isotope | One of several atomic forms of an element, each with the same number of protons but a different number of neutrons, thus differing in atomic mass. |
| Morphology | The study of the size, shape, and structure of animals, plants, and microorganisms and of the relationships of their constituent parts. |
| Vestigial Structure | A feature of an organism that is a historical remnant of a structure that served a function in the organism's ancestors. |
| Cladogram | A branching diagram showing the cladistic relationship between a number of species. |
| Lineage | Sequences of biological entities connected by ancestry-descent relationships. |
| Molecular Clock | A method of estimating the the time required for a given amount of evolutionary change, based on the observation that some regions of genomes evolve at constant rates. |
| Out-Group | A species or group of species from an evolutionary lineage that is known to have diverged before the lineage that contains the group of species being studied. |
| Phylogenetic Tree | A branching diagram that represents a hypothesis about the evolutionary history of a group of organisms. |
| Phylogeny | The evolutionary history of a species or group of related species. |
Created by:
Kendra R.
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