3.4.4 Genetic diversity and adaptation

Question 1

Define ‘genetic diversity’

Answer 1

The number of different alleles of each gene (within in a population )

Question 2

Apart from genetic factors what other type of factors causes variation within a species

Answer 2

Environmental (biotic and abiotic) factors

Question 3

What is a species?

Answer 3

A group of organisms with similar features that can interbreed to produce fertile offspring

Question 4

Explain how crossing over can contribute to genetic diversity

Answer 4

Sections of chromatids are exchanged.

Different sections have different alleles so new combinations of linked alleles are made.

Question 5

What can different species not do?

Answer 5

They cannot breed to produce fertile offspring as they have different genes and may have a different number of chromosomes

Question 6

What is a population

Answer 6

A population is a group of the same species in the same place that can interbreed

Question 7

Go through the stages of natural selection

Answer 7

1. A change in the environment causes a selection pressure
2. Random mutations produce genetic diversity
3. Some alleles provide an advantage
4. Those individuals with the advantageous alleles survive and reproduce
5. So the advantageous alleles are passed on
6. This means the frequency of advantageous alleles in the population increases

Question 8

Who decides what is the advantageous alleles?

Answer 8

The environmental conditions (nature)

Humans if selective breeding

Question 9

What is a selection pressure?

Answer 9

An environmental change that affects a population resulting in the death of some individual and the survival of those that are better adapted (those with favorable alleles)

Question 10

What are the 2 types of variation and give examples

Answer 10

• Continuous variation - a characteristic that an have a wide range of values shows continuous variation e.g. height, weight
• Discontinuous variation - a characteristic with few possible values shows discontinuous variation e.g. blood group

Question 11

Monogenic characteristics often show which type of variation

Answer 11

Discontinuous

Question 12

Polygenic characteristics often show which type of variation

Answer 12

Continuous

Question 13

Describe and explain how selection can affect the genetic diversity of a species

Answer 13

The genetic diversity is reduced as alleles have been chosen and rejected

Question 14

What is selection?

Answer 14

Selection is the process by which organisms that are better adapted to their environment survive, reproduce and pass on their genes

Question 15

Other than hunting give 2 reasons why populations might show low levels of genetic diversity.

Answer 15

1. population is small
2. inbreeding
3. population started with one pregnant female

Question 16

Index of diversity is higher in a hedge than a barley field - why?

Answer 16

1. more plant species
2. more food sources/variety of food
3. more habitats
4. More niches

Question 17

In a diploid organism phenotype (expressed characteristics) is determined by what?

Answer 17

Genotype (the combination of alleles present)

Question 18

What is meant by a low genetic diversity?

Answer 18

A small variety of different alleles.

Question 19

If there was no genetic diversity could natural selection occur?

Answer 19

No - because there would be no advantageous alleles.

Question 20

Define the term ‘gene pool’.

Answer 20

The total number of alleles in a population at any given time.

Question 21

What is directional selection and what does it result in?

Answer 21

1. Where selection favours individuals that vary in one direction from the mean of the population e.g. antibiotic resistant bacteria when using antibiotics.
2. This changes the characteristics of the population.

Question 22

What is stabilising selection and what does it result in?

Answer 22

1. Where selection favours individuals average individuals e.g. when environmental conditions are stable.
2. This preserves the characteristics of the population.

Question 23

When you plat continuous variation on a graph it will produce which type of curve?

Answer 23

A ‘normal distribution curve’.

Question 24

The 3 types of adaptations are…

Answer 24

1. Anatomical
2. Physiological
3. Behavioural

Question 25

Give an example of an anatomical adaptation.

Answer 25

Short ears and thick fur in arctic foxes.

Question 26

Give an example of a physiological adaptation.

Answer 26

Physiological = functional changes e.g. oxidising fats instead of carbohydrate in kangeroo rats to provide additional water in a hot environment.

Question 27

Give an example of a behavioural adaptation.

Answer 27

Autumn migration of swallows from U.K. to Africa to avoid winter food shortages.

Question 28

state 3 comparisons of genetic diversity

Answer 28

base sequence DNA
base sequence RNA
amino acid sequence of proteins

Question 29

other than hunting, suggest 2 reasons why populations might show very low levels of genetic diversity?

Answer 29

• inbreeding

- pop small to start off with