Chapter 9.2 A Mechanism for Evolution: Mutation ✓

Question 1

What is mutation?

Answer 1

A permanent change in the DNA sequence of a gene

Question 2

How does mutation contribute to evolution?

Answer 2

Mutation introduces new alleles into the gene pool, changing allele frequencies and providing variation that natural selection can act upon.

Question 3

What is a selection pressure?

Answer 3

A selection pressure is a biotic or abiotic factor that affects survival and reproduction, favouring individuals with beneficial traits.

Question 4

What is abiotic?

Answer 4

Non-living components

Question 5

What is biotic?

Answer 5

Living components

Question 6

What is meant by ‘survival of the fittest’?

Answer 6

It refers to individuals with advantageous traits surviving, reproducing, and passing on those traits to offspring.

Question 7

What happens to harmful, neutral, and beneficial mutations?

Answer 7

Harmful mutations are selected against and remain rare; beneficial mutations increase through selection; neutral mutations have no effect.

Question 8

What determines whether a mutation is beneficial or harmful?

Answer 8

Whether it helps an organism survive to reproduce in its environment.

Question 9

Why is mutation considered the ultimate source of genetic variation?

Answer 9

Because it creates new alleles that drive genetic diversity and evolutionary change.

Question 10

What is the example of mutation and selection seen in peppered moths?

Answer 10

During the Industrial Revolution, dark-coloured moths became more common due to better camouflage on soot-covered trees. After pollution was reduced, white moths regained an advantage.

Question 11

What is a population in biological terms?

Answer 11

A population is a group of individuals of the same species living in the same area who interbreed to produce fertile offspring.

Question 12

What causes phenotypic variation in a population?

Answer 12

Phenotypic variation is caused by genetic variation—differences in DNA sequences and alleles.

Question 13

Why is variation important in evolution?

Answer 13

Variation provides the raw material for natural selection; some traits may offer a survival or reproductive advantage.

Question 14

What is the source of genetic variation in populations?

Answer 14

Mutation introduces new alleles, creating genetic variation.

Question 15

How does the peppered moth illustrate the role of variation in evolution?

Answer 15

A mutation created a dark-coloured form that had a survival advantage in polluted environments, increasing its frequency in the population.

Question 16

Can a variation be beneficial in one environment and harmful in another?

Answer 16

Yes, the effect of a variation depends on the environmental context.

Question 17

What is the role of genes in inheritance?

Answer 17

Genes transmit phenotypes from one generation to the next.

Question 18

What are alleles?

Answer 18

Different forms of the same gene

Question 19

How do alleles contribute to variation in a population?

Answer 19

Individuals inherit different combinations of alleles, leading to variation in traits within the population.

Question 20

What is a gene pool?

Answer 20

Total collection of alleles within a population.

Question 21

What is a mutation? Give an example

Answer 21

A mutation is a permanent change in the DNA sequence of a gene. Example: The dark-coloured form of the B. betularia moth arose from a mutation that gave better camouflage during the Industrial Revolution.

Question 22

What is variation? Give an example

Answer 22

Variation is the difference in genotypes and phenotypes among individuals in a population. Example: Some moths in a population are dark-coloured, while others are light-coloured.

Question 23

What is population? Give an example

Answer 23

A population is a group of individuals of the same species living in the same area who can interbreed. Example: All B. betularia moths in a forest region of Britain.

Question 24

Compare mutation and crossing over as sources of variation.

Answer 24

Mutation creates new alleles by changing DNA, while crossing over reshuffles existing alleles during meiosis. Both increase genetic diversity, but in different ways.

Question 25

How do mutation and sexual reproduction contribute to variation?

Answer 25

Mutation introduces new alleles. Sexual reproduction (crossing over, independent assortment, random fertilisation) mixes alleles into new combinations.

Question 26

Explain the role of the white and dark form of B. betularia moths even after clean air legislations have been passed.

Answer 26

-Even after the Clean Air Acts reduced pollution, both white and dark forms of the moth remain in the population due to residual variation. -The dark form, once favoured due to its camouflage on soot-covered trees, is now more visible to predators, so its frequency has declined. -However, because both alleles still exist in the gene pool and selective pressures may change again, both forms are maintained, demonstrating how natural selection responds to environmental changes.

Question 27

Mutations are the ultimate source of variation. Explain the different ways in which sexual reproduction and mutation contribute to variation.

Answer 27

-Mutation changes the DNA sequence, creating new alleles that may provide survival advantages or disadvantages. -Sexual reproduction contributes to variation through independent assortment, crossing over during meiosis, and random fertilisation, all of which shuffle existing alleles into unique combinations in offspring. -Together, mutation introduces genetic novelty, while sexual reproduction increases the number of ways that alleles can be combined and passed on, enhancing diversity.

Question 28

Compare and contrast the types of variation in a population that results from mutation and crossing over.

Answer 28

-Mutation introduces entirely new alleles into the gene pool by altering DNA sequences. -These changes can be beneficial, harmful, or neutral and are the ultimate source of genetic variation. -Crossing over occurs during meiosis and involves the exchange of genetic material between homologous chromosomes. This shuffles existing alleles into new combinations but does not create new alleles. Comparison: -Both increase genetic diversity in a population. -Mutation introduces new alleles, while crossing over recombines existing alleles. -Mutation can affect the gene pool directly; crossing over influences phenotypic variety in offspring.