CCEA A Level Biology 2.3 Biodiversity Exam Questions

About CCEA A Level Biology 2.3 Biodiversity

Biodiversity, section 2.3 of Unit AS 2, covers how variety in living things is measured and classified. You need the three levels of biodiversity (genetic, species and ecosystem), how to calculate and interpret Simpson's index, and the principles of taxonomy: binomial nomenclature, the hierarchy of taxa and the definition of a species. CCEA also asks how phylogenetic relationships are found using morphology, cell structure and biochemistry, and the features of the five kingdoms with named examples such as Paramecium and Pleurococcus. The three domain system (Archaea, Bacteria, Eukarya) is also required. This links to human impact (2.4) and to Plantae and Animalia in A2 2.

What you need to know

• Levels of biodiversity Genetic diversity is variety of alleles within a species; species diversity combines the number of species and their relative abundance; ecosystem diversity is the range of habitats.
• Simpson's index D = 1 - sum of (n/N)^2, where n is the count or cover of each species and N is the total for all species. Values close to 1 indicate high diversity.
• Taxonomy Binomial names give genus then species, for example Homo sapiens. The hierarchy is kingdom, phylum, class, order, family, genus, species. A species is a group with common ancestry and close resemblance that can interbreed to produce fertile offspring.
• Phylogenetics Relationships are deduced from morphology and anatomy, cell structure, and biochemistry, especially DNA, RNA and amino acid sequences.
• Five kingdoms Prokaryotae (no nucleus, divide by binary fission); Protoctista (eukaryotic, unicellular or little differentiation, for example Paramecium and Pleurococcus); Fungi (chitin walls, hyphae, saprotrophic with extracellular digestion); Plantae (autotrophic, chloroplasts, cellulose walls); Animalia (heterotrophic, capable of movement).
• Three domains Archaea, Bacteria and Eukarya, based largely on biochemical differences such as rRNA sequences.

Common mistakes in 2.3 Biodiversity

• Writing binomial names incorrectly. The genus has a capital letter, the species name is lower case, and both are underlined or in italics.
• Saying species richness is the same as species diversity. Diversity also takes into account relative abundance.
• Forgetting to subtract the sum of (n/N)^2 from 1. Without that step a lower number would mean higher diversity, which reverses your conclusion.
• Putting fungi in the plant kingdom. Fungi have chitin walls, no chlorophyll and feed saprotrophically.
• Listing the hierarchy in the wrong order. Use kingdom, phylum, class, order, family, genus, species.

Try three 2.3 Biodiversity exam-style questions