OxfordAQA International A Level Biology 3.1.11 Biodiversity Within a Community Exam Questions

About OxfordAQA International A Level Biology 3.1.11 Biodiversity Within a Community

Biodiversity within a community closes Unit 1. You need to explain how genetic diversity can be measured by comparing DNA or mRNA base sequences, amino acid sequences and allele frequencies, and use these data to infer relationships. You also need to distinguish species richness from the index of diversity, recall and use the formula d = N(N - 1) / sum of n(n - 1), and discuss how human activities such as farming affect biodiversity. It links to species and taxonomy, variation and allele frequencies in Unit 3. Examiners usually set an index of diversity calculation and ask you to interpret it or evaluate a conservation trade-off.

What you need to know

• Genetic diversity Genetic diversity is the number of different alleles of genes in a population. It can be measured by comparing frequencies of measurable characteristics, base sequences of DNA or mRNA, the amino acid sequences of proteins, or allele frequencies.
• Species richness Species richness is the number of different species in a community. It does not take account of how many individuals of each species there are.
• Index of diversity d = N(N - 1) / sum of n(n - 1), where N is the total number of organisms of all species and n is the number of each species. A higher value means greater diversity. You must recall this formula.
• Human activity Farming often reduces biodiversity, for example by removing hedgerows, growing monocultures and using pesticides. Conservation measures must balance biodiversity with the need to produce food.
• Interpreting data Fewer differences in base or amino acid sequences suggest a closer relationship. Questions may give sequence alignments or tables of allele frequencies to compare.

Common mistakes in 3.1.11 Biodiversity Within a Community

• Confusing species richness with the index of diversity. Richness counts species only; the index of diversity also takes account of the number of individuals of each species.
• Forgetting the minus one in the index of diversity. Each term is n(n - 1), and the top is N(N - 1).
• Saying a monoculture has high genetic diversity. Crop monocultures are often genetically very similar, so genetic diversity is low.
• Treating DNA and amino acid comparisons as identical. Because the code is degenerate, some base differences do not change the amino acid sequence, so DNA comparisons can show more differences.

Try three 3.1.11 Biodiversity Within a Community exam-style questions