This free quiz has all 15 multiple choice questions from Section A of the OCR A Level Biology A Biological Diversity paper (H420/02), June 2023. It marks itself, so you get your score as soon as you finish.
What the multiple choice section covers
Tissues, stem cells and the cell cycle (2.1.6)
Measuring cells and comparing microscope resolution (2.1.1)
Dihybrid crosses and selective breeding in pedigree animals (6.1.2)
Gene regulation by the lac operon and homeobox genes (6.1.1)
Bacterial population growth plotted on a log scale (6.2.1)
Structure and roles of polysaccharides (2.1.2)
The binomial naming system (4.2.2)
Enzymes and coenzymes (2.1.4)
How to use it
Section A is worth 15 of the 100 marks in 2 hours 15 minutes, so aim to spend roughly 20 minutes on it. Examiners noted that many wrong answers came from misreading a single word or phrase in an option, so read every word of each option before committing. Paper 2 tests modules 1, 2, 4 and 6, so expect Year 12 and Year 13 content side by side.
Where students lost marks on this paper (from the OCR examiners' report and mark scheme)
These points cover the whole paper, not just the multiple choice section. Each is followed by wording that gained marks.
Growth of tissues, not cells: Many answers said mitosis is for growth or repair of 'cells', or gave cloning or differentiation, and extra incorrect detail cost the mark.
✔ Gains credit: growth and repair of tissues or organisms (both needed), or replacement of cells; simple, direct answers scored best.
Conservation increases biodiversity: Many candidates wrote that reintroducing a species 'maintains biodiversity', when in this case biodiversity is being increased.
✔ Gains credit: conservation involves active human intervention that restores or changes a habitat, ecosystem or its biodiversity.
Dilution is a single step: Many candidates proposed multi-step serial dilutions, could only think of 1 in 2 or 1 in 10 dilutions, or used 'serial dilution' for a simple proportional dilution.
✔ Gains credit: a single proportional dilution of the stock with distilled water, using volumes in the ratio worked out from the stock and target concentrations.
Repeatability must be comparative: A common mistake was to write 'the results are repeatable' in absolute terms, or to define terms without using the numbers in the table.
✔ Gains credit: comparative statements tied to the data, such as lower standard deviations at lower concentrations or earlier times showing results there are more repeatable.
Mention the active site: Many answers said immobilisation changes the enzyme's shape, tertiary structure or surface area, or that enzymes cannot move, without referring to the active site.
✔ Gains credit: immobilisation may change the shape of the active site or partly hide it, and substrate has to move through the matrix to reach the enzyme.
Explain why, not just how: Many candidates only described natural selection, and some said the antibiotic causes mutations, which was not credited.
✔ Gains credit: widespread use or overprescribing of antibiotics, low doses or unfinished courses, and the antibiotic acting as a selective agent; sharing of resistance genes on plasmids between bacteria was also credited.
Low oxygen favours denitrification: Only around 1 in 10 candidates linked low soil oxygen to denitrification; many wrote about respiration, and some said oxygen is needed for photosynthesis.
✔ Gains credit: low oxygen favours denitrifying bacteria, which convert nitrate to nitrogen gas, and reduces nitrification, so less nitrate is available to plants.
Keep practising
Try the multiple choice sections of the June 2023 AS paper and June 2023 Biological Processes paper, or practise by topic with the Genetics and Evolution, Biodiversity, Communicable Diseases, Cell Structure quizzes. You can also 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.
Practising recall is so important for retention and learning. Try this quiz without books first !