Topic 7- Types of selection

Question 1

What are the 3 types of selection?

Answer 1

Stabilising selection
Disruptive selection
Directional selection

Question 2

What is stabilising selection?

Answer 2

natural selection that keeps allele frequencies relatively constant over generations

Question 3

What does stabilising selection mean?

Answer 3

things stay as they are unless there is a change in the environment

Question 4

Give an example of stabilising selection

Answer 4

Human birth weights

Question 5

What is directional selection?

Answer 5

natural selection that produces a gradual change in allele frequencies over several generations

Question 6

What is directional selection usually caused by?

Answer 6

-a change in environment / selection pressures
- a new allele has appeared in the population that is advantageous

Question 7

What is disruptive selection?

Answer 7

natural selection that maintains high frequencies of two different sets of alleles (individuals with intermediate phenotypes or alleles are selected against)

Question 8

What does disruptive selection cause?

Answer 8

polymorphism

Question 9

Define polymorphism

Answer 9

the continued existence of two or more distinct phenotypes in species

Question 10

Where does disruptive selection occur?

Answer 10

an environment that shows variation