Factors Affecting The Evolution Of A Species

Question 1

What are the 5 factors that affect the evolution of a species?

Answer 1

1. Mutations.
2. Sexual selection.
3. Gene flow.
4. Genetic drift.
5. Natural selection.

Question 2

How do mutations affect the evolution of a species?

Answer 2

Causes the existence of different alleles and the formation of new alleles so causes genetic variation.

Question 3

How does sexual selection affect the evolution of a species?

Answer 3

It increases the frequency of alleles that code for characteristics that increase mating success.

Question 4

How does gene flow affect the evolution of a species?

Answer 4

This is the movement of alleles between populations and so immigration and emigration results in the changes of allele frequency in a population.

Question 5

How does genetic drift affect the evolution of a species?

Answer 5

This occurs in small populations and it is a change in the allele frequency due to the random nature of mutations. A new allele will have a greater impact in a smaller population than a bigger one where there is more alleles present in the gene pool.

Question 6

How does natural selection affect the evolution of a species?

Answer 6

This is the increase in the number of individuals that have characteristics that improves the chances of survival. Therefore, reproducing rates increase and so will the frequency of alleles coding for the characteristics.

Question 7

What is the impact of evolution in a small population? Variation?

Answer 7

The gene pool of a smaller population will have low genetic diversity due to little variety of genes/alleles. Some alleles that may have been rare in the original population may have an increased frequency in this smaller population. So decreases variation which endangers the process of natural selection and creates a bigger impact on the population in the future.

Question 8

What 2 things can the impact of a small population be seen in?

Answer 8

‘Bottleneck Effect’ and ‘Founder Effect’.

Question 9

What is the ‘Bottleneck Effect’?

Answer 9

An event that drastically decreases the size of a population due to a natural disaster/human activity. Population size shrinks before it increases again.

Question 10

What are 6 examples of the ‘Bottleneck Effect’?

Answer 10

• Earthquakes.
• Floods.
• Forest fires.
• Volcano erupting.
• Habitat destruction.
• Over-hunting.

Question 11

What is the process of the ‘Bottleneck Effect’ ?

Answer 11

1. Start with the original population and the original allele frequency.
2. A natural disaster or human activity reduces the population size.
3. The surviving population has different allele frequencies and little genetic diversity.
4. This difference in allele frequencies is reflected in today’s population.

Question 12

What is an advantage of the ‘Bottleneck Effect’?

Answer 12

A beneficial mutation will have a greater impact and leads to more development of a new species (role in our evolution).

Question 13

What is the ‘Founder Effect’?

Answer 13

The loss of genetic variation that occurs when a new population is established from a small number of individuals from a larger population. This smaller population may not contain all the different alleles that were present in the original larger population.

Question 14

What do the ‘Founder Effect’ and the ‘Bottleneck Effect’ both lead to?

Answer 14

‘Genetic Drift’.

Question 15

What is ‘Genetic Drift’?

Answer 15

A change in the allele frequency in a population due to random events (not selection pressures), so some alleles may be passed on, some may not.

Question 16

How do these 2 effects effect the gene pool size?

Answer 16

They make it smaller.

Question 17

What do these 2 effects not do?

Answer 17

They do not cause genetic mutations or the emergence of harmful alleles, but contribute to the increased frequency, but could also increase the beneficial alleles by chance.

Question 18

What is natural selection?

Answer 18

When some individuals within a population are better adapted to their environment than others due to differences in genotypes and phenotypes so increase the survival and reproduction rates and so pass on advantageous alleles which increase in a population over time.

Question 19

What are the 3 types of graphs which show the different types of natural selection?

Answer 19

1. Directional selection.
2. Stabilising selection.
3. Disruptive selection.

Question 20

What does the graph for directional selection look like?

Answer 20

The population after selection shifts left or right compared to the original population.

Question 21

What is the directional selection graph?

Answer 21

The selection or one extreme against another. When there is a change in the environment and the most common phenotype is no longer the most advantageous and organisms that are less common have more extreme phenotypes are positively selected. The allele frequency shifts towards the extreme phenotype and evolution occurs.

Question 22

What does the graph for stabilising selection look like?

Answer 22

The population after selection has become narrow in the middle compared with a spread out wide graph before selection.

Question 23

What is the stabilising selection graph?

Answer 23

The selection against the extreme phenotypes at both ends of the trait distribution. The two extreme phenotypes are on the end and the more likely phenotypes to survive are in the middle with the average at the peak of the new graph.

Question 24

What does the graph for disruptive selection look like?

Answer 24

The graph after selection has 2 peaks with a dip in the middle of them compared with a normal wide spread graph before the selection.

Question 25

What is the disruptive selection graph? (rare)?

Answer 25

The selection of extremes and against the mean. The extremes are selected for and the norms are selected against. The better phenotypes have better survival rates because the less advantageous phenotypes are attacked more (ones in the dip in the middle).

Question 26

What are on the axis of the different types of natural selection graphs?

Answer 26

• y axis: the number of individuals.
• x axis: the phenotype/trait.