4. Natural selection

Question 1

Genetic diversity

Answer 1

the number of different alleles of genes in a species or population

Question 2

Natural selection

Answer 2

When an allele codes for a characteristic that increases the chances of an organism surviving and reproducing, its frequency increases within a population

Question 3

Allele frequency

Answer 3

the proportion of the individuals that have one copy of anallele

Question 4

Reproductive success

Answer 4

the ability of an organism to have fertile offspring

Question 5

Randomly produced mutations resulting in new alleles of a gene can be:
Harmful
Neutral
Beneficial

Answer 5

Harmful – the individuals inheriting alleles with harmful mutations will die, so not pass on the mutation.

Some mutations are neutral – in the present environment the mutated allele neither harms nor hinders the organism.

Beneficial mutations increase the individual’s chance of survival, meaning they are more likely to reproduce and pass on the beneficial allele, the frequency of that allele will increase within the population. We say the new allele has increased the organisms REPRODUCTIVE SUCCESS

Question 6

Natural selection leads to populations becoming better adapted: 6pts

Answer 6

1. Randomly occurring mutations can result in new alleles being formed
2. Not all individuals are as likely to reproduce as each other. There is differential reproductive success in a population.
3. Individuals that have a beneficial allele that increase their chance of survival are more likely to survive, reproduce and pass on their genes (including the beneficial allele).
4. A greater proportion of the next generation inherits the beneficial allele. Their offspring in turn are also more likely to survive and pass on their genes.
5. The frequency of the beneficial allele increases from generation to generation.
6. Over many generations this leads to evolution as the advantageous alleles become more common in the population.