[18.3-4] natural selection, effects of selection on evolution Flashcards

1
Q

describe the core of natural selection?

A
  1. genetic diversity in a population due to random mutations (gene pool)
  2. ability to reproduce and pass on alleles (genes)
  3. selective pressures in the environment leads to differential survival
  4. those that have a selective advantage will be more likely to survive and reproduce, thus passing on advantageous alleles
  5. over many generations desired alleles will increase in frequency
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2
Q

what are selection pressures?

A

environmental factors that limit the polulation of a species

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3
Q

what are some examples of selection pressures? (3)

A
  • predation
  • disease
  • competition
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4
Q

what factors does the process of evolution by natural selection depend on?

A
  • organisms produce more offspring than can be supported by the available supply of food, light, space etc.
  • genetic variety within the populations of all species
  • variety of phenotypes that selection operates against
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5
Q

what are the 3 types of natural selection?

A
  • stabilising
  • directional
  • disruptive
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6
Q

draw the graph!

describe stabilising selection

A
  • favours average phenotype (phenotype around the mean)
  • selection against extreme phenotypes
  • tends to occur where the environmental conditions are constant over long periods of time
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7
Q

draw the graph!

describe directional selection

A
  • changes phenotype of a popuation
  • favours phenotypes that vary in one direction from the mean in the population ie. extreme phenotype
  • due to change in environmental condition
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8
Q

draw the graph!

describe disruptive selection

A
  • favours individuals with extreme phenotypes rather than those with phenotypes around the mean of the population
  • occurs when an environmental factor takes two or more distinct forms
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