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endemic (ecology)

Endemism is the ecological state of a species being unique to a defined geographic location, such as an island, nation, country or other defined zone, or habitat type; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. The extreme opposite of endemism is cosmopolitan distribution.



change (in a population) over time


what changes first, the phenotype or the genotype



list Darwin's three main postulates

• Genetic variation exists in a population.
• Survival is not random. Those individuals whose characteristics fit them best to their environment are likely to leave more offspring. Overproduction of offspring leads to a struggle for existence where only some of the offspring survive.
• The unequal ability of individuals to survive and reproduce will lead to changes in a population, with favorable characteristics accumulating overtime.



change within a species over time



the development of new species



a group of the same species living in the same place at the same time



a group of individuals that can interbreed and produce fertile offspring (individuals whose genes are capable of being pooled together... see what I did there?)


population genetics

field of study that investigates how populations change genetically over time


what two fields of study does population genetics join?

Darwin's evolutionary principles with Mendel's genetics


list the criteria required for a population to be in Harvey-Weinberg equilibrium

• Large population
• Isolated population (no immigration)
• No mutations
• Random mating (no sexual selection)
• No natural selective pressures - all individuals are equal in survival and reproductive success.


what is said of a population that meets all criteria of the Harvey-Weinberg principle?

it is at genetic equilibrium


what are the methods of sexual recombination?

crossing over, independent assortment and random fusion of gametes (fertilisation)


what does sexual recombination do to allele frequency within a population?

nothing, sexual recombination does not change allele frequency. on the other hand, sexual selection does affect allele frequency, as it is a selective pressure.


what is the purpose of sexual recombination?

while sexual recombination does not change overall allele frequency within a gene pool, it does produce great levels of variation at the individual level for selective pressures to operate upon.


list the processes that change allele frequencies

• random mutation
• natural selection (including sexual selection)
• genetic drift
• gene flow


mutations in which cells are most significant to evolutionary processes?

mutations in gametes, as these will be passed down to the next generation


explain why mutations that have large impacts on the phenotype are rare

because of DNA repair mechanisms, the redundant nature of the genetic code (silent mutations), the likelihood of a mutation showing up in protein coding regions of DNA, etc.


what are the classes of mutations?

• lethal: mutations that lead to the loss of alleles from a population, so they are never part of the gene pool
• neutral: mutations that do not benefit or harm the individual and do not aid in either survival or reproductive success of members of a population
• beneficial: mutations that lead to the survival and enhanced reproductive success of an individual (and thus the mutated allele)


what happens to mutations as environments change?

they may turn from neutral to beneficial, or beneficial to lethal, etc.


natural selection

the only mechanism that drives adaptive evolution - a process by which selection of certain phenotypes in a population allows some alleles in the gene pool to persist better than others, called adaptations. natural pressures are placed on the population causing some alleles to be lost and others to be favoured.


directional selection

one extreme is favored while the other is eliminated


adaptive evolution

a process by which selection of certain phenotypes in a population allows some alleles in the gene pool to persist better than others, called adaptations. natural pressures are placed on the population causing some alleles to be lost and others to be favoured.


stabilising selection

pressures are placed on both extremes of a population and the average is favoured


disruptive selection

where the pressures are placed on the average and the extremes are favoured


sexual selection

a subcategory of natural selection specific to reproductive success as it involves obtaining mates for sexual reproduction


intrasexual selection

sexual selective pressures exhibited within a sex (ex. males fighting amongst themselves for mating access)


intersexual selection

sexual selective pressures exhibited between sexes (ex. females choosing a male to mate with, which will pass that males genotype on instead of the less favoured male)


sexual dimorphism

Sexual dimorphism is a phenotypic difference between males and females of the same species. The prototypical example is for differences in characteristics of reproductive organs. Other possible examples are for secondary sex characteristics, body size, physical strength and morphology, ornamentation, behavior and other bodily traits. Traits such as ornamentation and breeding behavior found in one sex only imply sexual selection.


genetic drift

Genetic drift or allelic drift is the change in the frequency of a gene variant (allele) in a population due to random sampling. The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces. A population's allele frequency is the fraction of the copies of one gene that share a particular form. Genetic drift may cause gene variants to disappear completely and thereby reduce genetic variation.