3.4.4 Genetic diversity and adaptation

Question 1

What is genetic diversity?

Answer 1

The total number of different alleles present within a population / species

Question 2

What are the advantages of genetic diversity on a population?

Answer 2

The higher the diversity, the higher the chance for some of the population to be able to adapt to the new change in environment - allowing for natural selection ( some characteristics - alleles are more advantageous than others) and for individuals to pass on their allele

Question 3

What factors could increase genetic diversity?

Answer 3

Meiosis (crossing over, independent segregation)

Random fertilisation and fertilisation between individuals

Mutations

Gene flow - Introducing new alleles into a population when individual from another population migrate into it and reproduce

Question 4

What is a genetic bottleneck?

Answer 4

When an event causes a big reduction in population size which could reduce the allelic frequency (number of different alleles) in the gene pool which reduces genetic diversity

Question 5

What is the founder effect?

Answer 5

When a few organisms from a population start a new colony by migrating to different areas, meaning that the initial gene pool have a lower genetic diversity.

However, as individuals produce offspring and pass on their alleles, their allelic frequency may now be different to the other separated groups

Question 6

What could the founder effect be caused by?

Answer 6

Geographical separation

Religion (Humans)

Question 7

What is the process of natural selection?

Answer 7

1. Variation exists within a population
2. Variation can be increased through new mutations which result in new alleles being produced
3. Individuals with advantageous alleles will be more likely to survive to reproductive age as they are better able to obtain the resources they need
4. These individuals are more likely to reproduce
5. Advantageous allies are passed down to next generation by those individuals
6. There’s is an increase in allelic frequency of the advantageous alleles from generation to generation

Question 8

What is natural selection?

Answer 8

Organisms differ in their reproductive success

Question 9

How is polygenic characteristics modelled as?

Answer 9

Normal distribution

Question 10

What is stabilising selection?

Answer 10

Occurs in stable environment
Favours the mean characteristic - range and standard deviation decreases - graph gets narrower
E.g. birth weight

Question 11

What is directional selection?

Answer 11

Occurs in a slowly changing environment - occurs over a long period of time
Favours one of the extreme characteristic - change allele frequency - shifts mean position - doesn’t change standard deviation
E.g. Antibiotic resistance in bacteria

Question 12

What are changes brought about through selectional pressure?

Answer 12

Anatomical change
Biochemical/physiological change
Behavioural change