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What is a gene pool?
The complete set of unique alleles of genes in a population
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What is the gene frequency?
The frequency of occurence of an allele in relation to that of other alleles of he same gene in a population
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In large populations with random mating the gene frequency remains fairly stable. This is called...?
genetic equilibrium
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Through what ways can the gene frequency be changed?
- Mutations - new alleles are added to the gene pool
- Natural selection - a change in the environment can all of a sudden favour other alleles (eg the Peppered Moth)
- Gene migration - new alleles are introduced by immigrants from a different gene pool
- Non-random mating - inbreeding (which leads to an increased number of homozygous individuals with recessive traits)
- Genetic drift - a few individuals from a popluation become isolated. They do not have the complete range of alleles and after several generations, the gene frequency of the isolated group becomes distinctive from the original population
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What is a species?
A group of organisms that share common anatomical and physiological characteristics. They are able to interbreed and produce fertile offspring
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What is speciation?
The formation of a new species
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Describe speciation
- Large population of freeely interbreeding organisms
- A barrier cuts the popluation in half. No breeding (gene exchange) takes place between the two.
- Over time the two sub-populations change through natural selection and mutations
- After a while their gene pools totally change and evern if the barrier is removed, the two populations cannot interbreed and have become two different species
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What are the three types of barriers?
- Geographical - eg mountains, desert, seas
- Ecological - changes in temperature, pH, moisture
- Reproductive - mating at different times of the year, become sexually non-compatible
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