AQA GCSE Biology Paper 2 2025 Mark Scheme

Get the official AQA GCSE Biology Paper 2 Higher Tier (8461/2H) **June 2025 mark scheme (Version 1.0 Final)** — the examiner-approved document used to award marks across all **100 marks** of the exam. It includes full answers, level descriptors, calculations, and detailed examiner guidance for every question.

The mark scheme begins with examiner guidance on how answers are assessed. *Pages 2–6* explain marking principles such as “best fit” marking for extended responses, use of errors carried forward (ecf), handling alternative answers, and level-of-response descriptors for 6-mark questions.
For *Question 1 (pages 7–8)*, accepted answers include fossil formation through burial in sediment and mineral replacement, the correct classification terms **phylum** and **family**, and causes of extinction such as climate change, asteroid collisions, and habitat loss. The calculation confirms the ichthyosaur’s real length as **2.04 metres**.

Ecology and practical skills are covered in *Question 2 (pages 9–10)*. The mark scheme shows the correct calculation for soil water percentage (**28% at 20 m**) and explains that increasing distance from the tree increases soil water content. It also outlines valid improvements to investigations, such as repeating measurements and testing more locations.
Plant biology answers appear in *Question 3 (pages 11–13)*. The mark scheme defines geotropism as a growth response to gravity, identifies **auxin** as the controlling hormone, and explains how phototropism increases photosynthesis by allowing leaves to absorb more light and produce more glucose.

Human hormones and genetic engineering are assessed in *Question 4 (pages 14–15)*. Accepted responses include digestion of hGH by protease enzymes if swallowed, and detailed steps showing how the hGH gene is inserted into bacterial plasmids using enzymes during genetic engineering.

Environmental biology appears in *Question 5 (pages 16–17)*. The mark scheme defines biodiversity as the variety of species on Earth or within a habitat, and explains how peat bog destruction reduces biodiversity locally while contributing globally to climate change through release of carbon dioxide and methane.

Inheritance and reproduction are explained in *Question 6 (pages 18–20)*. The mark scheme identifies **cell division 1 as mitosis**, confirms that sperm cell J contains **23 chromosomes**, and explains why asexual reproduction produces genetically identical offspring while sexual reproduction increases genetic variation.
For the nervous system investigation in *Question 7 (pages 21–23)*, the calculation shows a mean reaction time of **181 milliseconds**. The mark scheme also explains the nervous pathway from receptor to sensory neurone, relay neurone, motor neurone, and muscle contraction when catching the ruler.

Genetics and protein synthesis are assessed in *Question 8 (pages 24–26)*. The Punnett square question confirms a **1 in 4 probability** of white offspring, while mutation questions explain how a DNA base change alters the enzyme active site so tyrosine can no longer bind.
The final section, *Question 9 (pages 27–28)*, evaluates Type 2 diabetes investigations. The mark scheme confirms the correct Hb-G value of **7.65%** for drug B after 12 weeks and outlines evaluation points comparing sample sizes, placebo controls, dosage differences, and effectiveness of both drugs.

Use this mark scheme to accurately mark your answers, understand examiner expectations, and improve extended-response techniques. Pair it with the AQA 8461/2H June 2025 question paper for complete exam preparation.

This document is designed for GCSE Biology students preparing for the 2026 exam series, particularly Year 11 students studying the AQA 8461 Higher Tier specification, as well as resit candidates and independent learners.

It is also ideal for teachers, tutors, and revision providers who need accurate mark schemes for marking mock exams, standardising grading, and teaching exam technique. It supports detailed feedback across ecology, genetics, inheritance, evolution, and response-control topics.