Natural Selection

Question 1

Natural selection

Answer 1

When an allele (that encodes for a characteristic which increases the chance of an organism surviving) increases in frequency in the population

Question 2

How are advantageous alleles created?

Answer 2

By mutations

Question 3

What is good about the advantageous allele?

Answer 3

It causes a certain phenotype which means the individual is more likely to survive in a given environment

Question 4

What happens in the environment to catalyse natural selection?

Answer 4

Selection pressures

Question 5

Selection pressures

Answer 5

Changes in environment (climate, habitats, food) that cause organism with advantageous allele to be more likely to survive in this new environment

Question 6

What happens if organisms with advantageous allele are more likely to survive?

Answer 6

They are more likely to reproduce and produce offspring which passes on advantageous allele

Question 7

The offsprings having the advantageous allele passed on means…

Answer 7

They can survive and reproduce to pass on allele which means this allele increases to next generation and next generation until it becomes the most common
Changes phenotype of this species as a result

Question 8

So what is required for evolution?

Answer 8

Adaptation (thanks to advantageous allele)
Selection (change in environment which allows this allele to be able to survive)

Question 9

Types of selection

Answer 9

Directional selection
Stabilising selection

Question 10

Directional shift

Answer 10

When individuals with alleles for EXTREME characteristics (on a continuum) is more likely to survive due to the selection pressure

Question 11

The effect of a directional shift

Answer 11

So this extreme allele is spread to next population thus the mean for this characteristic shifts in a direction to favour extreme
No change in the range

Question 12

Stabilising selection

Answer 12

When the allele encoding for a characteristic in the middle of a spectrum is advantageous
Given the selection pressure so organisms with these alleles are more likely to survive and reproduce

Question 13

Effect of stabilising selection

Answer 13

Frequency of this middle allele more likely to produce offspring with this
The mean does not shift because the mean is what was favoured
So the range of possible characterises will decrease