Genetic Diversity And Variation

Question 1

What is genetic diversity

Answer 1

Number of different alleles of a gene in a population

Question 2

What is a population

Answer 2

Group of interbreeding individuals of the same species

Question 3

What are the principles of natural selection

Answer 3

1. Variation of alleles exists in population due to random DNA mutations
   e. g. some bacteria contain gene for antibiotic resistance due to a mutation
2. Selection pressure / change in environment e.g. antibiotic introduced
3. Those with advantageous allele have increased chance of survival and reproduction – differential survival/reproductive success
   e. g. bacteria with gene for resistance survive and reproduce whilst those without it die
4. Those surviving / reproducing pass advantageous allele to offspring
5. Frequency of advantageous allele and (named) characteristic increases in the population
6. Over many generations / long period of time
   (evolution: change in allele frequency over time) and

Question 4

What is directional selection

Answer 4

Change to the environment
- Selection pressure acts one side
of the mean
- One extreme phenotype more
likely to survive and produce
- Bacteria with gene for
antibiotic resistance - Mean phenotype changes

Question 5

What is stabilising selection

Answer 5

• Stable environment
• Selection pressure acts either side of the mean
• Both extremes of phenotype less likely to
  survive and reproduce
• Very small or very large babies
• Mean phenotype remains the same

Question 6

How does large size lead to better adaption

Answer 6

Small surface area to volume ratio / more fat

Lose less heat (to the environment) / for insulation

Question 7

What is a very important adaption to consider when it comes to snow

Answer 7

Camouflage

Question 8

What is variation

Answer 8

Differences in characteristics between individuals within a species or between different species

Question 9

What is continuous variation

Answer 9

Small surface area to volume ratio / more fat

✓ Lose less heat (to the environment) / for insulation

Question 10

What is an example of discontinuous variation

Answer 10

Distinct, discrete categories

• Data tends to be qualitative
• Controlled by a single gene or a few genes
• Unaffected / not strongly influenced by the environment
• eg blood groups

Question 11

What can you compare to see the genetic diversity

Answer 11

Frequency of measurable and observable characteristics
The base sequence of DNA and mRNA
The amino acid sequence of the proteins encoded by DNA and mRNA

Question 12

What are the limitations of looking at frequency of measurable characteristics

Answer 12

Many observable characteristics coded for by more than one gene vary continuously
Difficult to distinguish

Characteristics could be modified by the environment so differences may be as a
result of different environmental conditions rather than different alleles.

Question 13

What do you need to do to get a representative sample

Answer 13

Random sample 
Large Sample size 
Statistical test used 
Standard deviation 
Mean

Question 14

What is an example of random sampling

Answer 14

Divide the area into a grid of numbered lines
- Using random numbers from a table, obtain a series of coordinates
- Take samples at the intersection of each pair of coordinates i.e. using
quadrats

Question 15

How is standard deviation interpreted

Answer 15

• The higher the value standard deviation, the higher the variation
• If standard deviations overlap, causing values of each set of data to be shared,
  any difference between the two may be due to chance