3.4.4 Genetic diversity and adaptations

Question 1

Define “genetic diversity”

Answer 1

The number of different alleles of each gene within a population

Question 2

Apart from genetic factors what other type of factors cause 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 offspirng 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 speicies in the same place that can interbreed

Question 7

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 he 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 individuals and the survival of those that are better adapted (those with favourable alleles)

Question 10

What are the two types of variation and give examples

Answer 10

Continuous variation - a characteristic than can have a wide range of values e.g. height, weight

Discontinuous variation - a characteristic with few possible values e.g. blood group

Question 11

Monogenic characteristics often show which type of varation

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 selction?

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. Interbreeding
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 diveristy?

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

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

This changes the characteristics of the population

Question 22

What is stabilising selection and what does it result in?

Answer 22

Where selection favours individuals average individuals e.g. when environmental conditions are stable

This preserves the characteristics of the populaion

Question 23

When you plot continuous variation on a graph, it will produce which type of cure?

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 furs in arctic foxes

Question 26

Give an example of a physiological adaptation

Answer 26

Physiological = functional changes

e.g. oxidising fats instead of carbohydrates in kangaroo rates to provide additional water in a hot environment

Question 27

Give an example of a behavioural adaptation

Answer 27

Autumn migration of swallows from UK 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