Diversity

Question 1

Explain the importance of genetic variation in the process of evolution.

Answer 1

Causes variation in phenotype some organisms are better have more favourable characteristics for environment
Natural selection of better adapted organisms survive and reproduce passing on genes
selection is due to different phenotypes being better suited to different environments;
eventually leads to species change/change in gene pool/change in gene frequencies

Question 2

Explain how natural selection produces changes within a species.

Answer 2

variation between members of population/species;
predation/disease/competition results in differential survival;
some have adaptations that favour survival;
survive to reproduce/have more offspring/ pass on their alleles/genes;
produces changes in frequency of allele /gene pool/genotypes/phenotypes;

Question 3

Explain how resistance to an antibiotic could become widespread in a bacterial population following a gene mutation conferring resistance in just one bacterium.

Answer 3

1. Frequent use of antibiotic creates selection pressure/ antibiotic kills bacteria;
2. Bacteria with mutation/ resistance have (selective) advantage over others / described;
3. (Survive to) reproduce more than other types;
4. Pass on advantageous allele/ mutated allele in greater numbers;
5. Frequency of (advantageous) allele increases in subsequent generations;

Question 4

Explain how selection can result in an insect population which is resistant to a particular insecticide.

Answer 4

Insecticide resistance already in population;
(resulting) from mutation;
resistant insects are not killed (by insecticide)/survive;
(And are able to) reproduce/breed;
passing on the relevant allele/gene to the next generation/offspring;
resulting in increasing frequency of resistance allele in population

Question 5

Describe how stabilising selection will affect the mean and standard deviation. Give the reason for your answer.

Answer 5

Mean – no change;
Standard deviation – decreases;
Reason – selects against/removes (both) extremes/extremes die/better survival of middle nos.;

Question 6

Explain what is meant by stabilising selection and describe the circumstances under which it takes place.

Answer 6

1. Occurs in an unchanging environment; 1
2. (Initial range of values in which) mean is best adapted;
3. Selection against extremes / selection for the mean;
4. Mean/median/mode unaltered
5. Range/S.D is reduced;
6. Repeated over many generations;
7. Increasing proportion of populations becomes well adapted to environment;