Genetic diversity and adaptation

Question 1

Define Genetic diversity

Answer 1

The total number of different alleles in a population

Question 2

Define genetic variation

Answer 2

The small differences in the DNA sequences between individual organisms within a species.

Question 3

How does genetic diversity lead to natural selection?

Answer 3

The greater the genetic diversity, the increased gene pool and mutations, leading to differential reproductive success in organisms

Question 4

What is the process of natural selection?

Answer 4

• random mutations occur within a population, producing new alleles of a gene and increasing the size of the gene pool
• There is a selection pressure
• Many mutations may be harmful but in some organisms, the possessor of this new allele may have an advantage over other individuals
• the individuals with the advantageous allele are more likely to survive and reproduce whereas the individuals without this allele, die and do not survive the selection pressure
• The advantageous allele is then passed on to the next generation
• over many generations, this allele increases in frequency

Question 5

What are the three types of natural selection?

Answer 5

• Directional selection
• Stabilising selection
• Disruptive selection

Question 6

What is directional selection?

Answer 6

Selection that favours individuals that vary in one direction from the mean of a population

Question 7

Explain what occurs due to directional selection?

Answer 7

• When there is an environmental change, individuals with a phenotype best suited for the new conditions survive and reproduce
• this results in a gradual change in allele frequency over several generations

Question 8

Give an example of directional selection

Answer 8

Antibiotic resistance
- there is a selection pressure which is the presence of antibiotics
- there is a growth in the population of bacteria, resulting in random mutations
- this arises the allele for antibiotic resistance, a beneficial allele in some bacteria
- bacteria with this allele are more likely to survive and reproduce whereas the other bacteria without this allele die
- this advantageous allele is then passed to the next generation and increases in frequency

Question 9

What is the outcome of antibiotic resistance

Answer 9

• non resistant bacteria decrease in population compared to resistant bacteria, shifting the normal distribution in the direction of antibiotic resistance

Question 10

What is stabilising selection?

Answer 10

• Selection that favours the average individuals, keeping allele frequencies constant over many generations
• this occurs when environmental conditions remain stable

Question 11

Give an example of stabilising selection

Answer 11

• Human birth weight
• The mass of babies born at a hospital were meausred over a 12 year period and at the same time infant mortality rate was measured against body mass
• the graph showed that at the extremes of body mass, there was a higher death rate showing that phenotypes that are average are more beneficial

Question 12

What are the three types of adaption natural selection causes

Answer 12

• anatomical
• physiological
• behavioural

Question 13

what is anatomical adaption and give an example

Answer 13

• structural or physical features
• an example is white thick fur for artic foxes

Question 14

What is physiological adaption and give an example

Answer 14

• A biological process
• an example is kangaroos oxidising fat instead of carbohydrates as a source of water in hot climates

Question 15

What is behavioural adaption and give an example

Answer 15

• A change in how an organism behaves
• an example is autumn migration of swallows from the UK to Africa to avoid food shortages