OCR A 4.2.1 · 21 written questions · 43 marks · about 50 minutes · marked as you go
This free quiz has 21 written exam questions on biodiversity, all taken from OCR A Level Biology A papers (AS and A level, 2018 to 2025). Short answers mark themselves. For longer answers you write your answer, then tick off the OCR mark-scheme points you made, so you see exactly where the marks are. This quiz covers the whole of OCR A 4.2.1: how biodiversity is measured at habitat, species and genetic level, how to sample a habitat, how to calculate and interpret Simpson's Index of Diversity, and why and how we conserve biodiversity.
What the quiz covers (OCR A spec 4.2.1)
Levels of biodiversity (4.2.1(a)): naming and defining habitat, species and genetic biodiversity.
Sampling (4.2.1(b)(i)(ii)): random, systematic and stratified sampling, choosing sampling sites and improving a field method.
Species richness and evenness (4.2.1(c)): defining both terms and reading them from quadrats and population graphs.
Simpson's Index of Diversity (4.2.1(d)): a full calculation, what a value of D tells you, and how recording errors change it.
Genetic biodiversity (4.2.1(e)): how genetic diversity is measured, the proportion of polymorphic gene loci, and why small populations lose diversity.
Threats and reasons to conserve (4.2.1(f)(g)): how agriculture reduces biodiversity, and ecological, economic and aesthetic reasons for conservation.
Conservation methods and agreements (4.2.1(h)(i)): in situ and ex situ conservation, CITES and the Convention on Biological Diversity.
How to use it
Write every answer in full, as you would in the exam: the mark for each question is shown, so you know how much to write. When you self-mark, only tick a point if your answer clearly makes it, then read the examiner's tip under each question. Your progress is saved on your device, so you can do it in two sittings, and at the end you can retry just the questions where you dropped marks.
Prefer multiple choice? Try the 27-question Biodiversity multiple choice quiz first.
Open the Biodiversity quiz in a new tab (easier on a phone)
Where students lose marks (from OCR examiners' reports and mark schemes)
Each point below is followed by wording that gained marks.
Count species, not individuals: Students often treat species richness as the number of individual organisms, so they count every plant or animal instead of the different kinds.
✔ Gains credit: Species richness is the number of different species present, e.g. 'there are six different species in the quadrat'.
Quadrat, not quadrant: When asked for sampling equipment, some students write 'quadrant', which OCR does not accept. A random number generator alone is not a piece of sampling equipment either.
✔ Gains credit: 'A (frame or point) quadrat', placed at random coordinates.
Name the level, then define it: Asked to name and define levels of biodiversity, students define the words 'species' or 'habitat', or give 'species richness' and 'species evenness' as the levels.
✔ Gains credit: 'Habitat biodiversity: the range of different habitats in an area' and 'species biodiversity: the richness and evenness of species in a community'.
No marks for just picking A or B: In comparison questions, students state which quadrat or area has higher evenness but give no reason. OCR never gives marks for a binary choice on its own.
✔ Gains credit: 'Evenness is higher in B because the number of individuals of each species varies less.'
Stick to the years asked: When a graph question names two years, many students describe every year in between and end up comparing the wrong data.
✔ Gains credit: A direct comparison of the two named years, e.g. 'there were more species in the later year, and the numbers of each species were closer together'.
Small population, small gene pool: Asked why few gene loci are polymorphic, students explain why the population declined instead of explaining what that did to the alleles. Some think a polymorphic locus is an allele that gives an advantage.
✔ Gains credit: 'The population became very small, so the gene pool is small and alleles are lost; inbreeding keeps the same alleles and only mutation can add new ones.'
Stratified sampling needs proportions: Students mention sampling each habitat but don't name stratified sampling, or leave out the calculation the question asks for.
✔ Gains credit: 'Use stratified sampling, with the number of samples in each habitat proportional to its area', supported by a calculation of the share for each habitat.
Lumping species together lowers D: Students say that recording several species as one changes 'the biodiversity' without saying how the calculated value of D, or the stage of the calculation, is affected.
✔ Gains credit: 'Σ(n/N)² is higher, so a bigger number is subtracted from 1 and D is lower.'
Keep practising
Try the Biodiversity multiple choice quiz, the Ecosystems and Populations multiple choice quiz, the The Immune System, Vaccines and Antibiotics written quiz or the Classification and Evolution written quiz, or browse all our OCR A Level Biology quizzes. Our OCR A masterclasses (Year 12 on Wednesdays at 5.15pm, Year 13 on Tuesdays at 6.30pm) work through real exam questions on one topic each week.
Questions, mark schemes and examiners' report extracts © OCR.