Evolution

Question 1

Define evolution.

Answer 1

1. cumulative change in heritable characteristics of a population
2. due to natural selection (descent with modification)

Question 2

Explain how sexual reproduction promotes variation in a species.

Answer 2

1. sexual reproduction involves interbreeding, so genetic material is from two parents;
2. new combinations of paternal and maternal chromosomes due to random fertilization;
3. which leads to new genetic combinations and therefore greater variation.
4. The variety of gametes is caused by crossing-over and by random orientation of alleles during meiosis.

Question 3

Explain the evolution of antibiotic resistance in bacteria.

Answer 3

1. resistance arises by random gene mutation;
2. so within populations, bacteria vary in their (genetic) resistance to antibiotics/fitness;
3. when antibiotics are used antibiotic-sensitive bacteria are killed;
4. and natural selection favours those with resistance;
5. meaning that resistant bacteria survive, reproduce and pass on the resistance allele.
6. Genes can also be transferred to other bacteria by plasmids.