Speciation and Genetic Drift

Question 1

What can cause genetic variation?

Answer 1

• mutation
• random fertilisation (crossing over, independent segregation)

Question 2

What is the effect of differential reproduction?

Answer 2

change in allele frequencies

Question 3

What is disruptive selection?

Answer 3

selection where individuals with alleles for either extreme trait are more likely to survive and reproduce

Question 4

What could disruptive selection lead to?

Answer 4

speciation

Question 5

What allows speciation to occur?

Answer 5

reproductive isolation, leading to 2 populations (of the same species) that cannot breed together

Question 6

What would reproductive isolation allow to occur?

Answer 6

speciation

Question 7

What are the 2 types of speciation?

Answer 7

allopatric and sympatric

Question 8

What is allopatric speciation?

Answer 8

geographical barriers cause reproductive isolation

Question 9

Explain the process of allopatric speciation

Answer 9

• 2 populations unable to breed together due to geographical barrier
• both populations acquire beneficial mutations, which are likely to be different due to the different environments / selection pressures
• over time, they become too genetically different to interbreed
• so they are now classed as different species

Question 10

What is sympatric speciation?

Answer 10

when reproductive isolation is caused by differences in behaviour

Question 11

What might cause sympatric speciation?

Answer 11

random mutations that lead to changes in reproductive behaviour such as courtship rituals or seasons of fertility

Question 12

What would different reproductive behaviours cause?

Answer 12

no gene flow between these individuals

Question 13

How does reproductive isolation lead to speciation?

Answer 13

• reproductively isolated populations accumulate different mutations
• DNA is so different that they are too genetically different to interbreed to produce fertile offspring
• classed as 2 different species

Question 14

What is genetic drift?

Answer 14

the change in allele frequency within a population between generations

Question 15

What does substantial genetic drift result in?

Answer 15

evolution

Question 16

What increases the impact changes in allele frequency have on a population?

Answer 16

the size of the population, smaller populations leads to greater impact

Question 17

Why does speciation occur when geographical boundaries prevent populations from breeding?

Answer 17

• environmental conditions/selection pressures are different
• so difference in beneficial alleles