Factors Affecting Evolution

Question 1

Mutation

Answer 1

Introduces new alleles and genetic variation.

Question 2

Gene flow

Answer 2

Involves the transfer of alleles between populations.

Question 3

Genetic drift

Answer 3

Causes random changes in allele frequencies, impacting small populations more significantly.

Question 4

Natural selection

Answer 4

Enhances the frequency of alleles that improve survival and reproductive success.

Question 5

Sexual selection

Answer 5

Increases the frequency of alleles that enhance reproductive success specifically.

Question 6

How do those factors influence evolution?

Answer 6

By altering allele frequencies

Question 7

Genetic drift:

Answer 7

• the random changes in allele frequencies within a population’s gene pool, due to chance events.
• Genetic drift does not occur as a result of natural selection.
• Particularly influential in small, isolated populations, where it can accelerate the development of new species.

Question 8

Large population means that:

Answer 8

• Large gene pools mean genetic diversity is high
• They can adapt effectively to changing selection pressures through natural selection

Question 9

Small population means:

Answer 9

• Small gene pool means genetic diversity is low
• They ae at risk of extinction when there are changes in selection pressures

Question 10

Categories for factors that limit population size:

Answer 10

• Density-dependent factors
• Density-independent factors

Question 11

Density-dependent factors:

Answer 11

These depend on the size of the population
- competition
- predation
- disease.

Question 12

Density independent factors:

Answer 12

These impact populations regardless of size, such as natural disasters and climate change.

Question 13

Bottleneck effect:

Answer 13

The bottleneck effect occurs when a population’s size reduces suddenly and drastically and this reduction lasts for at least one generation.

Question 14

Impacts of bottlenecks:

Answer 14

• It leads to a reduced gene pool and decreased genetic diversity compared to the original population.
• The decreased genetic diversity can cause issues related to inbreeding and reduced fertility.
• However, it may also allow a beneficial mutation to become more prevalent.

Question 15

Founder effect:

Answer 15

The founder effect occurs when a small group splits from a larger population, and a small new population is established by this small number of individuals.

Question 16

Potential impacts of the founder effect:

Answer 16

• It leads to a reduced gene pool and decreased genetic diversity compared to the original population.
• Rare alleles from the original population may become more common in the new population, whether they are beneficial, harmful, or neutral (an extreme example of genetic drift).

Question 17

Calculating allele frequency:

Answer 17

• Dominant allele frequency represented by p
• Recessive allele frequency represented by q

Allele frequency of p + q will always = 1

Question 18

Normal distribution:

Answer 18

Distribution of traits or characteristics of all living organisms show variation within populations. When plotted on graph, the different variants form a bell-shaped curve.

Question 19

Stabilising selection:

Answer 19

• The average is selected for positive selection
• Extremes are selected against in negative selection.
• Reduction in the frequency of alleles at extremes and an increase in average alleles

Question 20

Directional selection:

Answer 20

• Change in the environment and the normal (most common) phenotype is no longer the most advantageous.
• Organisms are less common and have extreme phenotypes are positively selected.
• The allele frequency then shifts towards the extreme phenotypes and evolution occurs.