Evolution in Populations and Speciation
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Created by:
musicme101 on April 11, 2012
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48 terms
Terms | Definitions |
|---|---|
 evolution | change in heritable traits in a population over time |
| population | groups of individuals of the same species living in the same space (smallest unit that can evolve over time) |
| species | group of populations whose members are capable of interbreeding and producing fertile offspring |
| gene pool | total collection of genes in a population at any time |
| microevolution | change in the gene pool over generations |
| population genetics | study of how populations change genetically over time |
| genetic drift | change in the gene pool of a population due to change |
| the two types of genetic drift | bottleneck and the founder effect |
| bottleneck | a type of genetic drift that leads to a loss of genetic diversity when a population is greatly reduced (survivors are luckier not better!) |
| founder effect | when a few individuals colonize a new habitat |
| gene flow | the movement of fertile individuals or gametes (like pollen or spores) between populations |
| mutation | a change in the nucleotide sequence of DNA; the ultimate source of genetic variation/new alleles |
| stablilizing selection | favors intermediate phenotypes and acts against extreme phenotypes (type of natural selection) |
| directional selection | acts against individuals at ONE of the phentype extremes (type of natural selection) |
| disruptive/diversifying selection | favors individuals at BOTH extremes of the phenotypic range and may occur in patchy habitats |
| sexual selection | a form of natural selection in which individuals with certain characteristics are more likely than others to obtain mates |
| sexual dimorphism | distinction in appearance, different secondary sexual characteristics (size, manes, horns) between males and females of a species |
| intrasexual selection | occurs between members of the same sex, usually males, where secondary sexual characteristics are used to compete for access to mates |
| intersexual selection (mate choice) | occurs between sexes where individuals of one sex (usually females) are choosy in selecting their mates, often selecting flashy or colorful mates |
| reproductive barriers serve to... | isolate a species' gene pool and prevent interbreeding |
| habitat isolation | (pre-zygotic barrier) 2 species live in the same general area but not in the same kinds of places |
| temporal isolation | (pre-zygotic barrier) 2 species breed at different times (different seasons, time of day etc) |
| behavioral isolation | (pre-zygotic barrier) there is little or no attraction for sexual attraction between species due to specific behaviors/traits |
| mechanical isolation | (pre-zygotic barrier) female and male sex organs not compatible |
| gametic isolation | (pre-zygotic barrier) female and male gametes not compatible |
| hybrid inviability | (post-zygotic barrier) when offspring fail to survive to maturity |
| hybrid infertility/sterility | (post-zygotic barrier) when hybrid offspring are sterile or have reduced fertility |
| hybrid breakdown | (post-zygotic barrier) when 1st generation of hybrids are viable and fertile, but the offspring of the hybrids are feeble or sterile |
| allopatric speciation | when populations of the same species are geographically separating gene pools |
| speciation only occurs when... | gene pool undergoes changes that establish reproductive barriers |
| smypatric speciation | when a new species arises without geographic isolation due to reduced gene flow from habitat differentiation or sexual selection |
| habitat differentiation | if the food sources are located in 2 different habitats, mating would become rare |
| adaptive radiation | when many diverse species evolve from a common ancestor |
| punctuated equilibrium | when fossil species appear suddenly, persist unchanged through several layers, then abruptly go through a speciation event |
| gradualism | when populations gradually evolve as they become more adapted to local environments; new species evolve slowly from an ancestral population |
| phylogeny | the evolutionary history of a species or group of species |
| convergent evolution | process where species from different evolutionary branches may come to resemble one another if they live in similar environments where natural selection favors similar adaptations |
| analogy | similarity due to convergent evolution, not because of common ancestry |
| biodiversity | variety of organisms considered at all levels of populations to ecosystems |
| systematics | classifies organisms and determines their evolutionary relationship |
| binomial nomenclature | two-part species name (genus and species identifier) |
| phylogenetic tree | hypothesis of evolutionary relationships within a group |
| cladistics | most widely used method in systematics where evolutionary descent is used to group organisms into clades |
| clade | group of species that includes an ancestral species and all it descendants |
| ingroup | the group of taxa being analyzed |
| outgroup | taxon before the lineage leading to the members of the ingroup |
| derived characters | evolutionary innovations that define branch points in the phylogeny of an ingroup |
| 3 domains | bacteria, archaea, eukarya |
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