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18.1: Key Terms

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    115112

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    adaptation
    heritable trait or behavior in an organism that aids in its survival and reproduction in its present environment
    adaptive radiation
    speciation when one species radiates to form several other species
    allopatric speciation
    speciation that occurs via geographic separation
    allopolyploid
    polyploidy formed between two related, but separate species
    aneuploidy
    condition of a cell having an extra chromosome or missing a chromosome for its species
    autopolyploid
    polyploidy formed within a single species
    behavioral isolation
    type of reproductive isolation that occurs when a specific behavior or lack of one prevents reproduction from taking place
    convergent evolution
    process by which groups of organisms independently evolve to similar forms
    dispersal
    allopatric speciation that occurs when a few members of a species move to a new geographical area
    divergent evolution
    process by which groups of organisms evolve in diverse directions from a common point
    gametic barrier
    prezygotic barrier occurring when closely related individuals of different species mate, but differences in their gamete cells (eggs and sperm) prevent fertilization from taking place
    gradual speciation model
    model that shows how species diverge gradually over time in small steps
    habitat isolation
    reproductive isolation resulting when species' populations move or are moved to a new habitat, taking up residence in a place that no longer overlaps with the same species' other populations
    homologous structures
    parallel structures in diverse organisms that have a common ancestor
    hybrid
    offspring of two closely related individuals, not of the same species
    hybrid zone
    area where two closely related species continue to interact and reproduce, forming hybrids
    natural selection
    reproduction of individuals with favorable genetic traits that survive environmental change because of those traits, leading to evolutionary change
    postzygotic barrier
    reproductive isolation mechanism that occurs after zygote formation
    prezygotic barrier
    reproductive isolation mechanism that occurs before zygote formation
    punctuated equilibrium
    model for rapid speciation that can occur when an event causes a small portion of a population to be cut off from the rest of the population
    reinforcement
    continued speciation divergence between two related species due to low fitness of hybrids between them
    reproductive isolation
    situation that occurs when a species is reproductively independent from other species; behavior, location, or reproductive barriers may cause this to happen
    speciation
    formation of a new species
    species
    group of populations that interbreed and produce fertile offspring
    sympatric speciation
    speciation that occurs in the same geographic space
    temporal isolation
    differences in breeding schedules that can act as a form of prezygotic barrier leading to reproductive isolation
    variation
    genetic differences among individuals in a population
    vestigial structure
    physical structure present in an organism but that has no apparent function and appears to be from a functional structure in a distant ancestor
    vicariance
    allopatric speciation that occurs when something in the environment separates organisms of the same species into separate groups

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