Natural Selection

Question 1

Define population

Answer 1

All the organisms of a particular species that live in the same place

Question 2

What is an allele

Answer 2

Different forms of a particular gene, found at the same locus on a chromosome. A single gene could have many alleles

Question 3

Define genetic diversity

Answer 3

The total number of different alleles in a population

Question 4

What advantage does a high genetic diversity provide

Answer 4

Ability to adapt to a change in environment, allows natural selection to occur

Question 5

Explain how natural selection results in development of new characteristics

Answer 5

• Random mutations result in new alleles
• Some alleles provide an advantage, making individuals more likely to survive and reproduce
• Their offspring receive the new allele, and frequency continues to increase over many generations

Question 6

What is directional selection

Answer 6

Occurs when environmental conditions change. Individuals with phenotypes suited to the new conditions will survive and pass on their genes. Over time the mean of the population will move towards these characteristics

Question 7

Give an example of directional selection

Answer 7

Antibiotic resistance in bacteria. The resistant bacteria survive, reproduce and increase the frequency of this allele and the population will shift to have greater antibiotic resistance

Question 8

What is stabilising selection

Answer 8

Occurs when environmental conditions stay the same. Individuals closest to the mean are favoured, and any new characteristics are selected against. This leads to a lack of diversity

Question 9

Give an example of stabilising selection

Answer 9

Birth weight. Babies that weigh around 3kg are more likely to survive compared to babies that weigh more or less than that