Chapters 22-25

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Terms in this set (77)
Homologous Structuressimilar structures that related species have inherited from a common ancestorVestigial Structuresstructures once necessary in ancestral forms, but no longer needed today.Evolutionary Treea diagram that reflects evolutionary relationships among groups of organismsConvergent Evolutionthe independent evolution of similar features in different lineagesAnalgoussimilar; alikeBiogeographyThe geographic distribution of speciesPangeathe super continent where all the continents were once joinedEndemicnative to or confined to a certain regionMicroevolutionchanges over time in allele frequencies in a populationGenetic VariationDifferences among individuals in the composition of their genes or other DNA segmentsAverage Heterozygositythe average percent of loci that are heterozygousGeographic VariationDifferences between the gene pools of geographically separate populations or population subgroups.ClineA graded change in a character along a geographic axis.Populationa group of organisms of the same species populating a given areaGene Poolall of the alleles in all the individuals that make up a populationHardy-Weinberg Principleprinciple that allele frequencies in a population will remain constant unless one or more factors cause the frequencies to changeGenetic DriftThe gradual changes in gene frequencies in a population due to random eventsFounder Effectchange in allele frequencies as a result of the migration of a small subgroup of a populationBottleneck EffectGenetic drift resulting from the reduction of a population, typically by a natural disaster, such that the surviving population is no longer genetically representative of the original population.Relative FitnessThe contribution of one genotype to the next generation compared to that of alternative genotypes for the same locus.Directional Selectionform of natural selection in which the entire curve moves; occurs when individuals at one end of a distribution curve have higher fitness than individuals in the middle or at the other end of the curveDisruptive Selectionform of natural selection in which a single curve splits into two; occurs when individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middleStabilizing Selectionform of natural selection by which the center of the curve remains in its current position; occurs when individuals near the center of a distribution curve have higher fitness than individuals at either endSexual SelectionA form of natural selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates.Sexual DimorphismA special case of polymorphism based on the distinction between the secondary sex characteristics of males and females.Intrasexual SelectionA direct competition among individuals of one sex (usually the males in vertebrates) for mates of the opposite sex.Intersexual SelectionSelection whereby individuals of one sex (usually females) are choosy in selecting their mates from individuals of the other sex; also called mate choice.Neutral Variationgenetic variation that does not appear to provide a selective advantage or disadvantageBalancing SelectionNatural selection that maintains stable frequencies of two or more phenotypic forms in a population (balanced polymorphism)Heterozygote AdvantageGreater reproductive success of heterozygous individuals compared to homozygotes; tends to preserve variation in gene pools.Frequency-Dependent SelectionA decline in the reproductive success of a morph resulting from the morph's phenotype becoming too common in a population; a cause of balanced polymorphism in populations.SpeciationThe process by which a new species evolves from a prior species, the most basic process in macroevolution.Microevolutionevolution resulting from small specific genetic changes that can lead to a new subspeciesMacroevolutionevolution on a large scale extending over geologic era and resulting in the formation of new taxonomic groupsBiological Species Concepta species concept defining a species as a population or group thereof whose members potentially interbreed and produce fertile offspringSpeciesgroup of similar organisms that can breed and produce fertile offspringReproductive Isolationseparation of species or populations so that they cannot interbreed and produce fertile offspringHybridsthe offspring of crosses between parents with different traitsPrezygotic BarriersA reproductive barrier that impedes mating between species or hinders fertilization if interspecific mating is attemptedPostzygotic BarriersAny of several species-isolating mechanisms that prevent hybrids produced by two different species from developing into viable, fertile adults.Morphological Species Conceptcharacterizes a species by its body shape, size, and other structural featuresEcological Species Conceptdefines a species as a set of organisms that are adapted to a particular set of resourcesPhylogenetic Species Conceptdefines a species as the smallest group of individuals that share a common ancestor, forming one branch on the tree of lifeAllopatric SpeciationGene flow is interrupted when a population is divided into geographically isolated subpopulationsSympatric SpeciationThe formation of a new species as a result of a genetic change that produces a reproductive barrier between the changed population (mutants) and the parent population. No geographic barrier is present.Polyploidythe condition in which an organism has extra sets of chromosomesAutopolyploidywhen an individual has more than two chromosome sets derived from a single speciesAllopolyploidA fertile individual that has more than two chromosome sets as a result of two different species interbreeding and combining their chromosomes.Hybrid Zonea geographic region in which members of different species meet and mate, producing at least some offspring of mixed ancestryReinforcementA process in which natural selection strengthens prezygotic barriers to reproduction, thus reducing the chances of hybrid formation. Such a process is likely to occur only if hybrid offspring are less fit than members of the parent species.Punctuated EquilibriaThe theory that species evolve during short periods of rapid changeMacroevolutionthe hypothesis that processes similar to those at work in microevolution can, over eons of time, transform an organism into a completely different kind of organismProtocellsdroplets with membranes that maintained an internal chemistry different from that of their surroundingsRibozymesRNA molecules that function as enzymesRadiometric Datingthe process of measuring the absolute age of geologic material by measuring the concentrations of radioactive isotopes and their decay productsHalf-Lifethe time required for one half of the atoms of a radioisotope to emit radiation an decay productsGeologic RecordThe division of Earth's history into time periods, grouped into three eons—Archaean, Proterozoic, and Phanerozoic—and further subdivided into eras, periods, and epochs.Stromatoliteslayered rocks that form when certain prokaryotes bind thin films of sediment togetherEndosymbiont Theoryexplains that eukaryotic cells may have evolved from prokaryotic cellsSerial EndosymbiosisA hypothesis for the origin of eukaryotes consisting of a sequence of endosymbiotic events in which mitochondria, chloroplasts, and perhaps other cellular structures were derived from small prokaryotes that had been engulfed by larger cells.Cambrian ExplosionA burst of evolutionary origins when most of the major body plans of animals appeared in a relatively brief time in geologic history; recorded in the fossil record about 545 to 525 million years ago.Plate TectonicsThe continents are part of great plates on Earth's crust that essentially float on the hot, underlying portion of the mantle.Mass Extinctionevent in which many types of living things become extinct at the same timePaedomorphosisThe retention in an adult organism of the juvenile features of its evolutionary ancestors.Homeotic GenesAny of the genes that control the overall body plan of animals by controlling the developmental fate of groups of cells.Adaptive Radiationsperiods of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological roles, or niches, in their communitiesHeterochronyEvolutionary change in the timing or rate of an organism's development.