Evolution may lead to speciation (18) Flashcards

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1
Q

What are 3 genetic factors that can cause phenotypic variation?

A

1) mutation of alleles
2) random fertilisation
3) random assortment of genetic material during meiosis

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2
Q

What factor, other than genetic factors, can also cause phenotypic variation?

A

environmental influences

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3
Q

What are 3 reasons for natural selection?

A

1) predation
2) disease
3) competition

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4
Q

How does natural selection cause a gene pool to change overtime?

A

organisms with advantageous characteristics are more likely to survive and pass favourable alleles to offspring so frequency of unfavourable alleles decreases

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5
Q

What is meant by speciation?

A

where a population is split and isolated and different selective pressures are placed on the groups so that the genetic make up changes to the extent that the 2 groups can no longer interbreed, causing them to become 2 separate species

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6
Q

What are the 2 types of speciation?

A

allopatric speciation
sympatric speciation

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7
Q

What is meant by allopatric speciation?

A

caused by a physical barrier (e.g. river, mountain range) so the environments occupied by the 2 groups are different and therefore different alleles are favoured

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8
Q

What is meant by sympatric speciation?

A

caused by a non-physical barrier (e.g. mutation no longer allowing 2 organisms to produce fertile offspring) so any changes in anatomy or behaviour may also prevent breeding

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9
Q

Why does genetic drift affect small populations more than large populations?

A

gene pool is smaller so there are less alleles available so any changes in frequency become pronounced very quickly

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10
Q

What is meant by genetic drift?

A

change in populations allele frequency that occurs due to chance rather than selective pressures (basically caused by a ‘sampling error’ during reproduction)

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11
Q

What are the 3 types of selection?

A

stabilising
directional
disruptive

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12
Q

What is stabilising selection?

A

when individuals closest to the mean are favoured so any new characteristics are selected against

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13
Q

What does stabilising selection cause?

A

low diversity

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14
Q

When does stabilising selection occur?

A

when environmental conditions stay the same

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15
Q

When does directional selection occur?

A

when environmental conditions change

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16
Q

What does directional selection cause?

A

overtime the mean of the population will move towards the more favourable characteristics for the new environment

16
Q

What is directional selection?

A

individuals with phenotypes suited to the new conditions will survive and pass on their genes

17
Q

What is disruptive selection?

A

opposite of stabilising as both extremes of the normal distribution are favoured over the mean

18
Q

What does disruptive selection cause?

A

overtime population becomes phenotypically divided

19
Q

What 3 factors cause genetic variation?

A

1) random fertilisation
2) crossing over
3) independent segregation