1. Calculating genetic biodiversity

2. Learning objective Success criteria To understand genetic biodiversity
Learners should be able to demonstrate and apply their knowledge and understanding of:
(e) how genetic biodiversity may be assessed, including calculations
To include calculations of genetic diversity within isolated populations, for example the percentage of gene variants (alleles) in a genome.
proportion of polymorphic = number of polymorphic gene loci gene loci total number of loci
Suitable populations include zoos (captive breeding), rare breeds and pedigree animals.

3. Genetic biodiversity Alleles – different versions of a gene
The more alleles present in a population, the more genetically biodiverse the population.
Species that contain greater genetic diversity are more likely to be able to adapt to changes in their environment. Why?
More likely to carry an advantageous allele

4. Factors affecting genetic biodiversity
For genetic biodiversity to increase the number of alleles in a population must also increase. This can occur through:
Mutation – creating a new allele
Gene flow – transferring alleles form one population to another through interbreeding

5. Factors affecting genetic biodiversity
For genetic biodiversity to decrease the number of alleles in a population must also decrease. This can occur through:
Selective breeding - (artificial selection)
Captive breeding programmes
Rare breeds
Artificial cloning - (asexual reproduction)
Natural selection – alleles coding for less advantageous characteristics will be lost from the population.

6. Genetic drift – evolution by chance
Evolution also occurs due to genetic drift.
In genetic drift chance decides which alleles are passed on
Evolution by genetic drift usually has a greater effect in smaller populations where chance has a greater influence

7. Genetic drift
In extreme cases it can lead to chance elimination of an allele from the population

8. Genetic bottleneck
Evolution by genetic drift can have a bigger effect if there is a genetic bottleneck, e.g. when a large population suddenly become smaller.

9. Founder effect
Where a small number of individuals can create a new colony, geographically isolated form the original. The new gene pool is small.

10. Measuring genetic biodiversity
Measure polymorphism (polymorphic genes have more than one allele e.g. the immunoglobulin gene determining blood group).
The proportion of genes that are polymorphic can be measured using the formula:
proportion of polymorphic = number of polymorphic gene loci gene loci total number of loci
Locus (plural – loci) the position of the gene on the chromosome
The greater the proportion of polymorphic gene loci, the greater the genetic biodiversity with the population

11. Questions
Describe how genetic biodiversity in a population can increase (2 marks)
Explain why it is advantageous for a species to be genetically biodiverse (3 marks)
A scientist was studying 2 species of Drosophila (flies). DNA was extracted from each species and 25 gene loci compared.
For species A, 12 of the loci studied were polymorphic.
For species B, 15 of the loci studied were polymorphic.
Use the data collected to explain which of the species was more genetically diverse. (4 marks)
summary questions on p 276 of the Oxford textbook

12. Answers
Describe how genetic biodiversity in a population can increase (2 marks)
Number of alleles in a population must increase (1)
Mutations can create new alleles (1)
Gene flow can introduce new alleles into the population (1)
summary questions on p 276 of the Oxford textbook

13. Answers
Explain why it is advantageous for a species to be genetically biodiverse (3 marks)
More genetically biodiverse a species is the greater variation in DNA/number of alleles present (1)
Species more likely to survive a change to the environment (1)
As there is a higher probability that some members of the species will have the allele to survive the change and reproduce (1)
summary questions on p 276 of the Oxford textbook

14. Answers Species A 48% of genes were polymorphic (1)
A scientist was studying 2 species of Drosophila (flies). DNA was extracted from each species and 25 gene loci compared.
For species A, 12 of the loci studied were polymorphic.
For species B, 15 of the loci studied were polymorphic.
Use the data collected to explain which of the species was more genetically diverse.
proportion of polymorphic = number of polymorphic gene loci
gene loci total number of loci
Species A 48% of genes were polymorphic (1)
Species B 60% of genes were polymorphic (1)
Species B more genetically diverse as it has a higher percentage of polymorphic genes (1)
Therefore more alleles are present (1)
summary questions on p 276 of the Oxford textbook