OCR A Level Biology A Paper 3 2025 Mark Scheme

Get the official OCR A-Level Biology A H420/03 Unified Biology mark scheme from the June 2025 examination series. This examiner-approved PDF contains the exact mark allocations, indicative scientific points, level-of-response criteria, calculation guidance, and assessment-objective breakdowns used by OCR examiners to assess candidate responses in the 2025 paper.

This mark scheme provides detailed examiner guidance for questions covering plant transport systems, cardiovascular physiology, muscle contraction, immunity, electrophoresis, genetic engineering, osmosis, β-thalassemia gene editing, climate change and vector-borne disease, and neutrophil responses. It includes accepted alternative answers, calculation tolerances, evaluation points, practical-skills expectations, and level-based essay descriptors for extended-response questions. Pair it with the matching OCR H420/03 June 2025 question paper on markscheme.net for complete examiner-style revision and exam preparation. Updated for the 2025/2026 academic year, mobile-friendly, and instantly downloadable from markscheme.net.

This document is designed for OCR A-Level Biology A students preparing for the 2026 examination series, Year 13 learners studying Unified Biology, retake students targeting A/A* grades, and home-schooled candidates seeking examiner-level insight into OCR marking expectations.

It is also essential for teachers, private tutors, revision-course providers, and parents supporting Biology revision at home. The mark scheme can be used for timed essay marking, practical-skills assessment, mock-exam grading, synoptic revision, and identifying weaknesses in OCR Biology A exam technique.