3.4.4 Genetic diversity and adaptation

Question 1

What is genetic diversity?

Answer 1

number of different alleles for a gene in a population

Question 2

What is the benefit of genetic diversity for a species survival?

Answer 2

increased chance of survival in a changing environment - due to a wide range of phenotypes

Question 3

Genetic diversity is required for…

Answer 3

natural selection to occur

Question 4

How does natural selection occur?

Answer 4

-genetic diversity in population
-new alleles arise due to random mutation
-the population experiences a selection pressure
-the individuals with the advantageous allele survive to reproduce
-the advantageous allele is inherited by the offspring
-over many generations, the advantageous allele increases in frequency in the population

Question 5

What is allele frequency?

Answer 5

how common an allele is in a population

Question 6

What is an allele?

Answer 6

a different version of a gene

Question 7

When does directional selection occur?

Answer 7

-selection pressure favours one phenotype
-over time advantageous allele increases in frequency and becomes dominant
-allele frequency continuously shifts in one direction (of one phenotype)

Question 8

When does stabilising selection occur?

Answer 8

-one phenotype is favoured
-most of population is clustered around a mean
-extreme phenotypes are removed
-smaller gene pool, due to less variety of alleles

Question 9

What is an example of stabilising selection?

Answer 9

mass of a human baby
-if too light, unlikely to survive
-if too heavy, the mother is unlikely to survive childbirth
-average baby about 7lbs

Question 10

What are the 3 types of adaptations?

Answer 10

-anatomical
-physiological
-behavioural

Question 11

Mutations can be…

Answer 11

harmful
neutral - do not impact survival
beneficial - the phenotype increases survival and reproductive stress

Question 12

What is an example of an anatomical adaptation?

Answer 12

structural features (e.g. fur colour)

Question 13

What is an example of a physiological adaptation?

Answer 13

internal mechanisms (e.g. rate of gas exchange)

Question 14

What is a behavioural adaptation?

Answer 14

actions to help survive and reproduce (e.g. courtship displays)

Question 15

Directional selection example

Answer 15

antibiotic resistance in bacteria

Question 16

How does speciation occur?

Answer 16

1. Geographical isolation
2. Separate gene pools / no interbreeding / gene flow between populations
3. Variation due to mutation
4. Different selection pressures / different abiotic / biotic conditions / environments / habitats
5. Differential reproductive success / selected organisms survive and reproduce
6. Leads to a change / increase in allele frequency