18.3- Natural selection

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  • Created by: Megan2413
  • Created on: 08-03-18 10:02
What are selection pressures?
The environmental factors that limit the population of a species
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Give three examples of selection pressures
- Predation - Disease - Competition
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What is the gene pool?
The total number of all alleles of the genes of all the individuals within a particular population at a given time
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What three factors affect the process of evolution by natural selection?
- organisms produce more offspring that can be supported by the available resources - genetic variety within the populations of all species - variety of phenotypes that can be selected against
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Why do organisms produce more offspring in terms of natural selection?
Where there are too many offspring for the available resources there is intraspecific competition for the limites resources available. The greater the numbers the greater the competition and the more individuals that will be selected against
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Why is genetic variety essential to natural selection?
Genetic variation allows there to always be a combination of favourable alleles even if environmental conditions change, so these individuals can reproduce and pass on their favourable alleles. This also prevents the species becoming extinct.
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How does genetic variety aid evolution?
Everytime individuals with a favourable combination of alleles in varying conditions are selected for and those less adapted are selected against, the species is evolving as the allele frequnecies change
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Give five steps on how natural selection allows allele frequency to change in a population depending upon the reproductive successess of individuals
1. There is competition within the population for environment resources that are limited 2. There is natural, genetic, variation within the population 3. Some individuals have an advantage of a favourable allele and this allows them to be better -->
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competitors for resources 4. These individuals are more likely to survive and reproduce and so will have more offspring -->
5. The favourable allele will be passed on to some of its offspring- as a result the frequency of this allele will increase in the population
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Other cards in this set

Card 2

Front

Give three examples of selection pressures

Back

- Predation - Disease - Competition

Card 3

Front

What is the gene pool?

Back

Preview of the front of card 3

Card 4

Front

What three factors affect the process of evolution by natural selection?

Back

Preview of the front of card 4

Card 5

Front

Why do organisms produce more offspring in terms of natural selection?

Back

Preview of the front of card 5
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