OCR A Level Biology Paper 2, Biological Diversity (H420/02), from June 2025 covers Modules 1, 2, 4 and 6: 100 marks in 2 hours 15 minutes, with 15 multiple-choice questions first. The question paper, mark scheme and examiners’ report are on the OCR past papers page, with a self-marking quiz of the multiple-choice section.
What the paper tested
Classification and evolution carried 22 marks (Question 21 and a 6-mark extended answer in 19(c)), biodiversity 18 (Question 18 on Simpson’s index in a meadow and Question 19 on puffins), patterns of inheritance 12 (Question 20, including epistasis), cloning and biotechnology 10, and cellular control 7 with a 6-mark question at 16(c). Question 16 opened with microscopy and stem cells, and Module 1 skills, sampling (PAG 3), microscopy calculations and significant figures, were worth around 20 marks.
Start with the classification and evolution written quiz, the biodiversity written quiz and the patterns of inheritance written quiz.
Where students lost marks
19(b)(ii) The effect of a puffin decline on other species (4 marks)
Most students got two marks for saying gull numbers would fall and fish numbers rise. Full marks went to those who followed the chain further: more fish means more competition among the species that eat fish, or less competition for the puffins’ competitors. General statements about ‘competition and predator-prey relationships’ scored nothing.
19(b)(iii) Why a predator helps long-term survival (2 marks)
Only a few students scored both marks. Most wrote about carrying capacity and food running out, which was the wrong idea. The answer was natural selection: the predator is a selection pressure, weaker individuals die, and the better adapted survive to pass on advantageous alleles. Students who wrote ‘genes are passed on’ rather than ‘alleles’ lost the mark, since all members of a species share the same genes.
20(a)(ii) Why epistasis changes offspring ratios (2 marks)
Most students scored zero. The successful few used the terms epistatic and hypostatic, explained that one gene masks the expression of another, and linked that to fewer distinct phenotypes. Gene and allele were frequently confused.
18(c)(ii) Interpreting a Simpson’s index value (2 marks)
Very few scored both marks because they described how to interpret the index in general instead of explaining what their own value from part (i) meant for this meadow. When a question says ‘explain the significance of the value you calculated’, use the number.
16(a) Microscopy (6 marks across three parts)
Students were asked for evidence that an image came from a light microscope; many cited the magnification, which does not rule out an electron microscope (the marks were for low resolution and a two-dimensional image). In the calculation, many forgot to divide by the magnification or slipped on the millimetre to micrometre conversion; the examiners suggest measuring in millimetres. On staining, few used the word ‘contrast’, and some pointed to a nucleus in a cell that was dividing. The {a('/exam-questions/ocr-a-level-biology-pag-1-microscopy-questions','PAG 1 microscopy questions')} cover all three skills.
Two multiple-choice questions
Q2, on the properties of water, produced an even spread of wrong answers. Q7 showed a Euglena cell; few recognised it as a protoctist, with many choosing Plantae despite the flagellum and the lack of unicellular plants.
How to use this paper
Sit it timed, 2 hours 15 minutes, and mark it strictly. Retry the multiple-choice section on the quiz page a week later.
Read the examiners’ comments on the parts you lost marks on. On this paper the pattern was answering in general terms when the question asked for a specific explanation: the chain of effects in a food web, the meaning of your own calculated value, the mechanism behind epistasis.
Work the big topics with the OCR exam questions by topic and the written quizzes.
Convert your mark with the OCR grade boundaries.
Questions and examiners’ comments are summarised from OCR’s published question paper, mark scheme and report for H420/02 June 2025, © OCR.