Evolution

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What is the gene pool?
The complete range of alleles present in a population.
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What is allele frequency?
How often an allele occurs in a population, usually given as a percentage of the total population.
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What is evolution?
The change in allele frequency in a population over a period of time,
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What is the process of evolution?
1. Variation in alleles caused by mutations. 2. Selection pressures create survival struggle. 3. Better adapted individuals more likely to survive. 4. Advantageous alleles survive, passed onto offspring. 5. Frequency of advantageous allele increases.
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What is stabilising selection?
When environment isn't changing much, individuals will alleles towards the middle of range are more likely to survive, leads to reduction of possible phenotypes.
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What is directional selection?
Due to change in environment, individuals will alleles for characteristics of an extreme type are more likely to survive and reproduce.
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What factors affect evolution?
Mutation, sexual selection, gene flow, genetic drift, natural selection.
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What is genetic drift?
The process whereby an allele becomes more common in a population due to chance.
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What are genetic bottlenecks?
An event e.g. natural disaster, that causes a big reduction in population size, leading to gene pool reduction.
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What is the founder effect?
Small populations arise due to establishment of new colonies by isolated individuals, extreme example of genetic drift, smaller gene pools, less variation, any rare alleles from original population in new one will have bigger impact during selection.
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What is the Hardy-Weinburg Principle?
Has to be large population and needs to be random mating.
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What are the Hardy-Weinburg equations?
p+q=1 and p^2+2pq+q^2=1
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What is artificial selection?
When humans select individuals in a population to breed together to get desirable traits.
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Give examples of artificial selection.
Modern dairy cattle - female with high milk yield + male whose mother had high milk yield. Select offspring with highest milk yield. Carried on for many generations. Same with bread wheat.
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What are the issues with artificial selection?
Gene pool is reduced (potentially useful alleles can be lost), health problems for organisms, genetic diseases, over-exaggeration of certain traits.
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What is speciation?
The development of a new species.
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What is a species?
A group of similar organisms that can reproduce to give fertile offspring.
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What is allopatric speciation?
When populations are reproductively isolated through a combination of geographical separation and natural selection.
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How does reproductive isolation occur?
Seasonal changes, mechanical changes, behavioural changes.
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What is sympatric speciation?
Speciation without geographic isolation.
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Other cards in this set

Card 2

Front

What is allele frequency?

Back

How often an allele occurs in a population, usually given as a percentage of the total population.

Card 3

Front

What is evolution?

Back

Preview of the front of card 3

Card 4

Front

What is the process of evolution?

Back

Preview of the front of card 4

Card 5

Front

What is stabilising selection?

Back

Preview of the front of card 5
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