Roles of genes and environment in evolution

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  • Created by: Steff06
  • Created on: 18-06-16 16:59
What environmental factors can limit the growth of a population?
Space, availability of food, light, minerals or water, predation and infection by pathogens.
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What do these factors offer?
Offer environmental resistance.
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What are the 2 types of factors?
Abiotic (non-living) and biotic (living).
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What will happen if environmental resistance is great enough?
The population size will shrink.
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What will happen if the population size shrinks?
Competition will be reduced and the population will grow which will cause more competition and the population will fall again.
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Describe selection pressure
An environmental factor that confers greater chances of survival to reproductive age on some members of the population.
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What is stabilising selection?
Where natural selection keeps things the way they are by selecting the individuals that will survive and reproduce. Unlikely a new phenotype will arise and confer an advantage.
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What happens when the environment changes?
The selection pressure changes.
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What is directional selection?
Where the selection pressure changes as the environment changes an the allele frequency changes. Leads to evolutionary change.
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Describe the ways a large population of organisms can be split into sub-groups.
Geographic barriers e.g. rivers or a mountain range. Seasonal barriers e.g. climate change. Reproductive mechanisms e.g. no longer able to mate.
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What will happen eventually to the 2 sub-populations?
They will not be able to interbreed and will be different species.
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How can genetic drift lead to large changes in small populations?
Alleles can be eliminated from the population in a single generation.
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Describe genetic drift
Fluctuations or changes in the allele frequency. For example as the size of the population decreases, the degree of fluctuation will increase.
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What are the negatives regarding genetic drift?
Reduces genetic variation, can reduce ability of a population to survive in a new environment. Contribute to extinction or lead to the production of a new species.
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How do small populations occur in nature?
A natural disaster such as a volcanic eruption or a disease pandemic may cause a population bottleneck.
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Card 2

Front

What do these factors offer?

Back

Offer environmental resistance.

Card 3

Front

What are the 2 types of factors?

Back

Preview of the front of card 3

Card 4

Front

What will happen if environmental resistance is great enough?

Back

Preview of the front of card 4

Card 5

Front

What will happen if the population size shrinks?

Back

Preview of the front of card 5
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