[OLD] Populations - Evolution Flashcards

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1
Q

Describe allopathic speciation. (9 points)

A

Geographical isolation.
Creates separate gene pools with no interbreeding.
Variation due to mutation.
Different selection pressures
Selection for different advantageous alleles.
Differential reproductive success.
Leads to change in allele frequency.
Occurs over a long period of time.
Populations no longer able to interbreed.

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2
Q

What are the 4 factors that cause speciation?

A

Isolation
Mutation
Selection
Time

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3
Q

What happens to the allele frequency in stabilising selection?

A

It doesn’t change.

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4
Q

What type of selection is likely to lead to the development of new species?

A

Disruptive

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5
Q

What type of selection leads to a change in the mean?

A

Directional

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6
Q

What type of phenotypes are favoured in disruptive selection?

A

Extreme phenotypes.

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7
Q

What is the equation for allele frequency?

A

p + q = 1

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8
Q

What happens to allele frequencies in disruptive selection?

A

They increase.

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9
Q

Which phenotypes are favoured in stabilising selection?

A

Intermediate phenotypes.

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10
Q

What is a selective pressure?

A

A factor that drives selection

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11
Q

Why is hybridisation rarely successful?

A

Because of differences in the gene pools. If offspring are produced, they are rarely fertile.

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12
Q

Give the 2 main causes of geographical isolation.

A

Migration caused by overcrowding

Geographical hazards e.g volcanic eruptions, earthquakes, rivers, islands, roads

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13
Q

Describe sympatric speciation. (7 points)

A

Occurs in the same population.
Mutations cause variation.
Reproductive separation with no gene flow.
Different alleles selected.
Change in allele frequency.
Disruption selection.
Eventually different species which cannot interbreed.

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14
Q

What type of isolation occurs in sympatric speciation?

A

Reproductive isolation.

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15
Q

How does reproductive isolation cause speciation?

A

Individuals in the 2 populations may not be able to court each other, or mate with each other or produce fertile offspring. Now breeding can only occur with each gene pool, not between them.

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16
Q

Why is sympatric speciation more common in plants than animals?

A

Plants exhibit polyploidy and self fertilisation.

17
Q

What kind of animals has sympatric speciation been seen in?

A

Insects e.g hawthorn fly and apple fly

18
Q

What is genetic drift?

A

Genetic drift is the change in allele frequencies that doesn’t depend on selective pressures - the change is due to a random occurrence.

19
Q

What causes genetic variation?

A

mutations
meiosis - formation of chiasmata, paring up of homologous chromosomes
random fertilisation of gametes

20
Q

What should an evolution answer always start with?

A

There is genetic variation within all living organisms.

21
Q

What factors affect the survival of an organism?

A

Availability of food, water, shelter, mates

Disease

22
Q

What are the three types of selection?

A

Stabilising, disruptive, directional.

23
Q

What is the T test used for?

A

To compare the mean values of 2 sets of data.

24
Q

What is balanced polymorphism?

A

When 2 distinct forms are present in a population.

25
Q

What is balanced polymorphism caused by?

A

Disruptive selection.

26
Q

Give 2 main types of isolation that occur during speciation.

A

Geographical isolation

Reproductive isolation

27
Q

Give 2 examples of reproductive isolation.

A

Temporal - different breeding seasons or mating activity at different times.
Behavioural - different mating rituals.

28
Q

Give examples of a selection preside that could cause directional selection.

A

Habitat change
Predation
New disease

29
Q

What type of environment is likely to cause disruptive selection?

A

Fluctuating

30
Q

What type of environment is likely to cause stabilising selection?

A

Stable

31
Q

What type of environment is likely to cause directional selection?

A

Slowly changing in one direction.

32
Q

Why are post-zygotic isolation mechanisms inefficient for the organisms involved?

A

They have invested time, energy and resources into passing on their alleles but it is wasted as the offspring either doesn’t develop or can’t pass on its own alleles.

33
Q

Why are post-zygotic isolation mechanisms more of a problem for rare organisms?

A

It is likely to lead to their extinction, as they cannot afford to waste resources on unsuccessful mating.