Evolution may lead to speciation

Question 1

Genetic factors that cause phenotypic variation within a species

Answer 1

1. Mutation of alleles
2. Random fertilisation by gametes
3. Random assortment of genetic material during meiosis

Question 2

Why does natural selection occur?

Answer 2

1. Predation
2. Disease
3. Competition

All result in differential survival and reproduction

Question 3

How does natural selection cause a change in a population’s gene pool over generations?

Answer 3

Organisms with advantageous characteristics are more likely to survive & pass their favourable alleles to offspring. Frequency of unfavourable alleles decreases

Question 4

What is Stabilising selection?

Answer 4

Occurs when environmental conditions stay same. Individuals closest to mean are favoured, & any new characteristics are selected against. Results in low diversity

Question 5

What is Directional selection?

Answer 5

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

Question 6

What is disruptive selection?

Answer 6

Opposite of stabilising selection, in that both extremes of normal distribution are favoured over mean. Over time, population becomes phenotypically divided.

Question 7

Define Speciation

Answer 7

Where population is split & isolated, there are different selective pressures on two groups. If genetic makeup changes to extent two groups can no longer interbreed, they have become separate species.