[OLD] Populations - Evolution

Question 1

Describe allopathic speciation. (9 points)

Answer 1

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.

Question 2

What are the 4 factors that cause speciation?

Answer 2

Isolation
Mutation
Selection
Time

Question 3

What happens to the allele frequency in stabilising selection?

Answer 3

It doesn’t change.

Question 4

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

Answer 4

Disruptive

Question 5

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

Answer 5

Directional

Question 6

What type of phenotypes are favoured in disruptive selection?

Answer 6

Extreme phenotypes.

Question 7

What is the equation for allele frequency?

Answer 7

p + q = 1

Question 8

What happens to allele frequencies in disruptive selection?

Answer 8

They increase.

Question 9

Which phenotypes are favoured in stabilising selection?

Answer 9

Intermediate phenotypes.

Question 10

What is a selective pressure?

Answer 10

A factor that drives selection

Question 11

Why is hybridisation rarely successful?

Answer 11

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

Question 12

Give the 2 main causes of geographical isolation.

Answer 12

Migration caused by overcrowding

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

Question 13

Describe sympatric speciation. (7 points)

Answer 13

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.

Question 14

What type of isolation occurs in sympatric speciation?

Answer 14

Reproductive isolation.

Question 15

How does reproductive isolation cause speciation?

Answer 15

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.

Question 16

Why is sympatric speciation more common in plants than animals?

Answer 16

Plants exhibit polyploidy and self fertilisation.

Question 17

What kind of animals has sympatric speciation been seen in?

Answer 17

Insects e.g hawthorn fly and apple fly

Question 18

What is genetic drift?

Answer 18

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

Question 19

What causes genetic variation?

Answer 19

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

Question 20

What should an evolution answer always start with?

Answer 20

There is genetic variation within all living organisms.

Question 21

What factors affect the survival of an organism?

Answer 21

Availability of food, water, shelter, mates

Disease

Question 22

What are the three types of selection?

Answer 22

Stabilising, disruptive, directional.

Question 23

What is the T test used for?

Answer 23

To compare the mean values of 2 sets of data.

Question 24

What is balanced polymorphism?

Answer 24

When 2 distinct forms are present in a population.

Question 25

What is balanced polymorphism caused by?

Answer 25

Disruptive selection.

Question 26

Give 2 main types of isolation that occur during speciation.

Answer 26

Geographical isolation

Reproductive isolation

Question 27

Give 2 examples of reproductive isolation.

Answer 27

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

Question 28

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

Answer 28

Habitat change
Predation
New disease

Question 29

What type of environment is likely to cause disruptive selection?

Answer 29

Fluctuating

Question 30

What type of environment is likely to cause stabilising selection?

Answer 30

Stable

Question 31

What type of environment is likely to cause directional selection?

Answer 31

Slowly changing in one direction.

Question 32

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

Answer 32

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.

Question 33

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

Answer 33

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