18.4- Effects of different forms of selection on evolution

?
  • Created by: Megan2413
  • Created on: 11-03-18 21:33
What is stabilising selection?
It preserves the average phenotype (phenotype around the mean) of a population by favouring average individuals (selection against the extreme phenotypes)
1 of 17
What is directional selection?
It changes the phenotypes of a population by favouring phenotypes that vary in one direction from the mean of the population (selection for one extreme phenotype)
2 of 17
What is disruptive selection?
It favours individuals with extreme phenotypes rather than those with phenotypes around the mean of the population
3 of 17
Does stabilising selection allow evolutionary change?
No
4 of 17
What must the environmental conditions be for stabilising selection to occur?
Environmental conditions remain the same over a long period of time
5 of 17
How does constant environmental conditions allow for stabilising selection?
If environmental conditions never change, the average phenotype is advantageous and the extremes will be selected against as they will never be advantageous if the environmental conditions don't change
6 of 17
Will the mean remain the same after stabilising selection?
Yes
7 of 17
Does the range remain the same after stabilising selection?
No- it decreases
8 of 17
How does directional selection occur?
When environmental conditions change, individuals with the new favourable phenotype will lie to the right or left of the current mean
9 of 17
What happens to the mean value after directional selection?
It moves to the side of the mean with the new favourable phenotype being selected for
10 of 17
What happens to the range after directional selection?
It generally doesn't change
11 of 17
What is a common example of directional selection?
Antibiotic resistance
12 of 17
Is disruptive selection te most or least important type of selection for bringing about evolutionary change?
Most important
13 of 17
When does disruptive selection occur?
When an environmental factor takes two or more extreme forms, which could lead to speciation
14 of 17
Which phenotypes are selected against?
The phenotypes around the mean
15 of 17
Which phenotypes are selected for?
The phenotypes at the extremes
16 of 17
What happens to the mean after disruptive selection occurs?
Two or more new means are created as there are new favourable phenotypes for each extreme environmental condition
17 of 17

Other cards in this set

Card 2

Front

What is directional selection?

Back

It changes the phenotypes of a population by favouring phenotypes that vary in one direction from the mean of the population (selection for one extreme phenotype)

Card 3

Front

What is disruptive selection?

Back

Preview of the front of card 3

Card 4

Front

Does stabilising selection allow evolutionary change?

Back

Preview of the front of card 4

Card 5

Front

What must the environmental conditions be for stabilising selection to occur?

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Populations and evolution resources »