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AP Biology

Unit 7 Evolution and Natural Selection

QuestionAnswer
Adaptation The close fit between an organism and its environment.
Biodiversity Biological diversity; the total number of species, or, more broadly, the diversity of genetic sequences, cell types, metabolism, life history, phylogenetic groups, communities, and ecosystems.
Phylogenetic Tree A tree-like diagram representing a hypothesis about the evolutionary relationships among populations or species.
Node In phylogenetic trees, the point where a branch splits, representing the common ancestor from which the descendant species diverged.
Root The base of a phylogenetic tree, representing the common ancestor or group from which all the organisms on the tree evolved.
Selective Pressure The full set of environmental conditions, both abiotic and biotic, that influence the evolution of a population by natural selection.
Convergent evolution The independent evolution of similar traits in different species as a result of similar environments or selective pressures.
Artificial selection A form of directional selection similar to natural selection, but with selection done intentionally by humans, usually with a specific goal in mind, such as increased milk yield in cattle.
Sexual selection A form of selection that promotes traits that increase an individual’s ability to find and attract mates.
Genetic Drift A random change in the frequency of an allele due to chance.
Bottleneck An extreme, usually temporary, reduction in population size that may result in marked loss of genetic diversity and, in the process, genetic drift.
Founder Effect A type of genetic drift that occurs when only a few individuals establish a new population.
Migration The movement of individuals from one population to another or to areas with no prior population.
Gene Flow The movement of alleles from one population to another through interbreeding between members of each population.
Nonrandom mating Mate selection that is not random, but instead is based on genotype or relatedness.
Hardy-Weinberg Equilibrium A state in which allele and genotype frequencies do not change over time, implying the absence of evolutionary forces. It also specifies a mathematical relationship between allele frequencies and genotype frequencies.
Morphological Homology An anatomical structure that is similar in two groups of organisms because it was present in the common ancestor of the two groups and retained over evolutionary time.
Molecular Clock The observation that the extent of genetic divergence between two groups is a reflection of the time since the groups shared a common ancestor.
Vestigial Structure A structure that has lost its original function over time and is now much reduced in size.
Fossil The remains of a once-living organism.
Carbon-14 A radioactive isotope of carbon frequently used in radiometric dating.
Radiometric Dating Dating ancient materials using the decay of radioisotopes as a yardstick, including the decay of radioactive to nitrogen for time intervals up to a few tens of thousands of years, and the decay of radioactive uranium to lead for most of Earth history.
Half-life The time it takes for an amount of a substance to reach half its original value. Radioactive half-life is the time it takes for half of the atoms in a given sample of a substance to decay.
Invasive Species Non-native species that become established in new ecosystems.
Phylogeny The history of descent with modification and the accumulation of change over time.
Cladogram A type of phylogenetic tree that shows clades, or monophyletic groups.
Character An anatomical, physiological, or molecular feature of an organism that varies among taxa.
Shared Character A character or trait that is present in two or more groups of organisms.
Derived Character A character or trait that is newly evolved; an evolutionary innovation.
Outgroup A group of organisms that has an older common ancestor than the common ancestor of the group of interest, and therefore serves as a reference for evolutionary relationships within the group of interest.
Biological Species Concept (BSC) The concept that “species are groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups.” The BSC is the most widely used and accepted definition of a species, but cannot be applied to asexual.
Niche A complete description of the role a species plays in its environment, and of its requirements, both abiotic and biotic.
Prezygotic Describes factors that prevent the fertilization of an egg.
Postzygotic Describes factors that cause the failure of a fertilized egg to develop into a fertile individual.
Speciation The process whereby new species are produced.
Divergent Evolution The process by which two groups of organisms become genetically and physically different from each other over time.
Allopatric Describes populations that are geographically separated from each other.
Sympatric Describes populations that are in the same geographic location.
Adaptive Radiation A period of unusually rapid evolutionary diversification in which natural selection accelerates the rate of speciation within a group, with new species adapted for specific niches.
Gradualism The idea that species change slowly over time.
Punctuated Equilibrium The idea that species go through periods of relatively little change, which are interrupted by short periods of rapid change and diversification.
Extinction The loss of a group of organisms, typically a species.
RNA world hypothesis The idea that the earliest cells relied on RNA for both information storage and catalysis.
Created by: DrStokes
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