AQA A Level Biology - Populations (HW)

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9 Terms

1
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define species

  • a group of similar organisms that can reproduce to give fertile offspring

  • exists as 1 or more populations


2
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define population

group of organisms of the same species living in the same area at the same time that can interbreed

3
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define gene pool

complete range of alleles present in a population

4
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define allele frequency

how often an allele occurs in a population

5
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what is the hardy-weinberg principle?

  • principle that predicts the frequency of alleles in a population does not change from 1 generation to the next (predicts no change and the frequencies)

  • describes hypothetical situation in which there is no change in the gene pool and no evolution


6
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what assumptions are required to use the hardy weinberg principle?

  • organisms are diploid and reproduce sexually

  • alleles are not sex linked and are equally distributed between both species

  • large population to minimize random sampling errors

  • random mating, no mating preference for certain geno/phenotypes

  • no mutation of the allele occurs

  • no migration so no exchange of genes between the population and another population must not occur

  • no natural selection and no favouring of certain characteristics

  • gene only has two alleles


7
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what is the hardy-weinberg equation for allele frequency?

  • p + q = 1

    • where p is the frequency of 1 allele, normally dominant

    • and q is the frequency of the other allele, normally recessive


8
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what is the hardy weinberg equation for genotype frequency?

  • p² + 2pq + q² = 1

  • p² → frequency of homozygous dominant genotype

  • 2pq → frequency of heterozygous genotype

  • q² → frequency of homozygous recessive genotype

  • also works if alleles are codominant or if you don’t know which is which (D or r) as p and q are arbitrary


9
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what can the hardy-weinberg equations be used for?

  • predicting allele frequency

  • predicting genotype frequency

  • predicting phenotype frequency

  • predicting percentage of the population that has a certain genotype

  • showing if any external factors are affecting allele frequency - if this principle is used 2x to show allele frequency has changed between two generations, the principle will not apply