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23 Cards in this Set
- Front
- Back
evolution
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change in allelic frequencies within a population over time
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Evolution acts on _______s, not ________s
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populations; individuals
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descent with modification
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changes over time produced modern species from ancestral species
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vestigial trait
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a reduced or incompletely
developed structure in an organism that has no function or reduced function, but is clearly similar to functioning organs or structures in closely related species |
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structural homology
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similarities in adult morphologies
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When does speciation occur?
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occurs when populations of the same species become genetically isolated by lack of gene flow and then diverge from each other due to natural selection, genetic drift, or mutation
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What constitutes a distinct species?
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populations that are reproductively isolated from each other, have
distinct morphological characteristics, or form independent branches on a phylogenetic tree |
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biological species concept
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populations are evolutionarily independent if they do not interbreed
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prezygotic factor
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a mechanism that prevents mating or fertilization
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postzygotic factor
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a mechanism that prevents development or viable or fertile adults (i.e. ligers)
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Types of prezygotic factors
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1) Habitat Isolation
2)Temporal Isolation (different breeding times) 3) Behavioral 4) Morphological 5) Gametic (sperm-egg incompatibility) |
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Types of postzygotic factors
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1) Hybrid zygote inviability
2) Hybrid sterility 3) Hybrid “breakdown” •Genetic incompatibility with self or parents •Behavior inappropiate to be recognized by either parent •Is ecologically intermediate between parent species |
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allopatric speciation
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speciation occurs in geographic isolation
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sympatric speciation
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speciation within a panmictic
population |
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founder effect
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a special kind of allopatric
speciation in a small isolated population on the edge of a species range |
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parapatric
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speciation in adjacent populations with gene flow
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polyploid
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an organism with multiple sets of chromosomes
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autopolyploid
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produced because of a mutation that causes a doubling of chromosome number
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allopolyploid
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individuals created when
parents that belong to different species produce an offspring in which chromosome number doubles |
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Aneuploidy
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Duplication or loss of an individual chromosome
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Paralogues
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two genes within an organism that have arisen from the duplication of a single gene in an ancestor
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Orthologues
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reflects conservation of a single gene from a common ancestor
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Horizontal gene transfer (HGT)
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Genes hitchhike from other species
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