Evolution

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What is a gene pool?
The sum total of all the genes in a population at any given time.
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What is allele frequency?
The relative frequency of a particular allele in a population.
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What is the purpose of the Hardy-Weinburg principle?
It models the mathematical relationship between the frequencies of alleles and genotypes in a theoretical population that is stable and not evolving.
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What factors affect the evolution of a species and how do they affect it?
Mutation: formation of new alleles. Sexual selection: increased frequency of successful alleles. Gene flow: movement of alleles by immigration/emigration. Genetic drift: random mutation. Natural selection: increased frequency of successful alleles.
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What factors can affect population size? (Give examples of each)
Density-dependent factors: competition, predation, parasitism, communicable disease. Density-independent factors: climate change, natural disasters, seasonal change, human activities.
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What are population bottlenecks?
Large reductions in population size which last for at least one generation. The gene pool, and genetic diversity are greatly reduced.
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What is the founder effect?
An extreme example of genetic drift where small populations can arise due to the establishment of new colonies by a few isolated individuals.
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How are alleles affected by the founder effect?
The new, small populations have much smaller gene pools than the original population and display less genetic variation. If carried to the new population, the frequency of rare alleles in the original population will be higher in the new population.
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On a graph, what does a bell-shaped curve denote?
A normal distribution.
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What is stabilising selection?
Where the average is selected for and the extremes are selected against.
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What is directional selection?
When one extreme is selected for, and the average and the other extreme are selected against.
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What is disruptive selection?
When the extremes are selected for and the average is selected against.
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What is speciation?
The formation of new species through the process of evolution.
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What events lead to speciation?
Members of the population become isolated and no longer interbreed: no gene flow. Alleles within the groups undergo random mutations: different environments resulting in different selection pressures. Large changes in phenotype.
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What is allopatric speciation?
The geographical isolation of members of a population. The environments are different and so selection pressures result in different physical adaptations.
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What is sympatric speciation?
The reproductive isolation of members of a population within a habitat. (More common in plants). When members of two different species interbreed and form fertile offspring- this hybrid won't be able to breed with members of either parent population.
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What are reproductive barriers?
Things formed within a population, before or after fertilisation has occured, that prevent successful interbreeding.
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How do prezygotic reproductive barriers affect successful interbreeding?
They prevent fertilisation and the formation of a zygote.
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How do postzygotic reproductive barriers affect successful interbreeding?
Reduce the viability or reproductive potential of offspring.
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What are polymorphic populations?
Populations that display more than one distinct phenotype.
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What is a wild type allele?
The allele coding for the most common/normal characteristic.
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What is artifical selection?
Where humans apply a specific selection pressure.
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Why is selective breeding used?
To produce offspring with desirable characteristics (e.g. in farming).
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What are some of the ethical considerations surrounding the use of artificial selection?
Some species (e.g. dogs) are artificially selected for their looks leading to health issues (e.g. the pug). Limited gene pool so exaggerated characteristics and unwanted traits are also selected for.
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What is inbreeding?
The breeding of closely related individuals.
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What are some problems caused by inbreeding?
Limited gene pool- decreased genetic diversity. Increase of homozygous reccessive alleles leading to genetic disorders- reduced survival and reproductive ability.
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What are seed banks and what are gene banks?
Seed banks keep samples of seeds and gene banks store other biological samples such as sperm or eggs.
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How are gene banks helpful?
The alleles they contain are used to increase genetic diversity-a process called outbreeding (breeding unrelated or distantly related varieties is also a form of outbreeding).
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How does outbreeding correct the problems caused by inbreeding?
It reduces the occurrence of homozygous recessives and increases the potential to adapt to environmental change.
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Card 2

Front

What is allele frequency?

Back

The relative frequency of a particular allele in a population.

Card 3

Front

What is the purpose of the Hardy-Weinburg principle?

Back

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Card 4

Front

What factors affect the evolution of a species and how do they affect it?

Back

Preview of the front of card 4

Card 5

Front

What factors can affect population size? (Give examples of each)

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