Source: https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-4-the-heart [Revision notes](https://senecalearning.com/en-gb/revision-notes.md) › [A Level](https://senecalearning.com/en-gb/revision-notes/a-level.md) › [Biology](https://senecalearning.com/en-gb/revision-notes/a-level/biology.md) › [AQA](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa.md) › The Heart # The Heart Biology: AQA A Level, topic 3.4.4 ## Structure The heart is the muscular organ that pumps blood to and from the lungs and around the body. The heart consists of four chambers and each chamber is very important. ### Right atrium ![Right atrium](https://image-v2.cdn.app.senecalearning.com/2018-03/c9affe19-3c38-4275-9b74-28eb5455efc1/9.2.1%20Heart%20structure.jpg) - Deoxygenated blood flows into the right atrium from the body. - The vein that pumps deoxygenated blood into the right atrium is called the vena cava. - The right atrium is the first chamber that deoxygenated blood flows through. ### Right ventricle ![Right ventricle](https://image-v2.cdn.app.senecalearning.com/2018-03/c9affe19-3c38-4275-9b74-28eb5455efc1/9.2.1%20Heart%20structure.jpg) - When the walls of the right atrium contracts, deoxygenated blood flows into the right ventricle. - The atrioventricular valves prevent blood from flowing back into the atria from the ventricles. - Then the walls of the right ventricle contracts, blood is pumped out of the pulmonary artery to the lungs. - The semi-lunar valves prevent blood from flowing back into the right ventricle from the pulmonary artery. ### Left atrium ![Left atrium](https://image-v2.cdn.app.senecalearning.com/2018-03/c9affe19-3c38-4275-9b74-28eb5455efc1/9.2.1%20Heart%20structure.jpg) - Oxygenated blood flows into the left atrium from the lungs. - The vein that pumps oxygenated blood into the left atrium is called the pulmonary vein. ### Left ventricle ![Left ventricle](https://image-v2.cdn.app.senecalearning.com/2018-03/c9affe19-3c38-4275-9b74-28eb5455efc1/9.2.1%20Heart%20structure.jpg) - When the walls of the left atrium contracts, oxygenated blood flows into the left ventricle. - The atrioventricular valves prevent blood from flowing back into the atria from the ventricles. - The walls of the left ventricle are considerably thicker than the right ventricle. - The left ventricle has to transport blood all the way around the body but the right ventricle only has to transport blood to the lungs. ### Aorta ![Aorta](https://image-v2.cdn.app.senecalearning.com/2018-03/c9affe19-3c38-4275-9b74-28eb5455efc1/9.2.1%20Heart%20structure.jpg) - When the left ventricle contracts, blood is pumped out of the heart to the rest of the body. - Oxygenated blood leaves the heart through the aorta. - The semi-lunar valves prevent blood from flowing back into the left ventricle from the aorta. ## The Cardiac Cycle The flow of blood from the lungs to the heart and around the body is called the cardiac cycle. The cardiac cycle is the continuous relaxing and contracting of the heart. The steps involved are: ### 1) Atrial contraction ![1) Atrial contraction](https://image-v2.cdn.app.senecalearning.com/courseImages/biology/2.3.2%20-%20The%20heart%20and%20circulatory%20system/2.2.7%20The%20heart%20(s1)%20(1)-min.jpg) - Blood from the lungs flows into the left atrium and blood from the body flows into the right atrium simultaneously. - The atria contract, increasing the pressure in the atria. - The blood in the atria is forced into the ventricles. - The ventricles are relaxed and fill with blood. ### 2) Ventricular contraction ![2) Ventricular contraction](https://image-v2.cdn.app.senecalearning.com/courseImages/biology/2.3.2%20-%20The%20heart%20and%20circulatory%20system/2.2.7%20The%20heart%20(s1)%20(1)-min.jpg) - The atria relax and the ventricles start to contract. - Contraction of the ventricles causes the pressure inside the ventricles to increase. - The pressure shuts the atrioventricular valves so that blood does not flow back into the atria. - The blood in the ventricles is forced out of the ventricles and out of the heart through the pulmonary artery or the aorta. ### 3) Relaxation ![3) Relaxation](https://image-v2.cdn.app.senecalearning.com/courseImages/biology/2.3.2%20-%20The%20heart%20and%20circulatory%20system/2.2.7%20The%20heart%20(s1)%20(1)-min.jpg) - The blood in the pulmonary artery and the aorta is at high pressure. -The pressure shuts the semi-lunar valves so that blood does not flow back into the ventricles. - Both the ventricles and the atria relax and the atrioventricular valves reopen. - Blood flows into the ventricles and the atria from the pulmonary vein and vena cava. ### 4) Repeat ![4) Repeat](https://image-v2.cdn.app.senecalearning.com/courseImages/biology/2.3.2%20-%20The%20heart%20and%20circulatory%20system/2.2.7%20The%20heart%20(s1)%20(1)-min.jpg) - The cycle continues. ## Interpreting Data At each stage in the cardiac cycle, the pressure and volume of the atria and ventricles changes considerably. These changes can be presented as a change over time. ### Pressure in the atria ![Pressure in the atria](https://image-v2.cdn.app.senecalearning.com/2018-08/5413b9a9-7d12-4cf8-83c4-84eb2d40c619/pressure-862180_1920.jpg) - When the atria contract, the pressure in the atria increases. - When the atria relax and the ventricles contract, the pressure in the atria decreases. - When both the atria and the ventricles relax, there is a slight increase as the atria fill with blood again. ### Pressure in the ventricles ![Pressure in the ventricles](https://image-v2.cdn.app.senecalearning.com/2018-08/5413b9a9-7d12-4cf8-83c4-84eb2d40c619/pressure-862180_1920.jpg) - When the atria contract, the pressure in the ventricles is relatively low. There is a slight increase in pressure as the ventricles fill with blood. - When the ventricles contract, the pressure increases dramatically. The pressure increases considerably more than when the atria contract. - When both the atria and the ventricles relax, there is a slight increase as the ventricles fill with blood again. ### Volume in the atria ![Volume in the atria](https://image-v2.cdn.app.senecalearning.com/courseImages/physics/5.2.2%20Characteristics%20of%20the%203%20kinds%20of%20emission/blood-1813410_640.jpg) - When the atria contract, the volume in the atria decreases. - When the atria relax and the ventricles contract, the volume in the atria increases again. - When both the atria and the ventricles relax, there is a slight decrease when blood flows into the ventricles from the atria. ### Volume in the ventricles ![Volume in the ventricles](https://image-v2.cdn.app.senecalearning.com/courseImages/physics/5.2.2%20Characteristics%20of%20the%203%20kinds%20of%20emission/blood-1813410_640.jpg) - When the atria contract, the volume in the ventricles increases slightly as they fill with blood. - When the ventricles contract, the volume decreases dramatically. The volume decreases considerably more than when the atria contract. - When both the atria and the ventricles relax, the volume increases as the ventricles expand again. ## Test yourself on The Heart - What direction of blood flow is halted by the semi-lunar valves? - Stages in the Cardiac Cycle - Where does blood flow when the atria contract? - What causes the significant decrease in volume in the ventricles? - Which of the following statements about the cardiac cycle are true? [Practise this topic for free](https://app.senecalearning.com/classroom/course/d0ce0c30-6417-11e8-8edc-d9cd1c890408/section/bfa5fd77-cf33-4381-81fe-9f691784d81b/session) - Previous topic: [3.4.3 The Circulatory System](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-3-the-circulatory-system.md) - Next topic: [3.4.5 Blood Vessels](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-5-blood-vessels.md) ## Biology: AQA A Level contents ### 1 Biological Molecules - 1.1 Monomers & Polymers - [1.1.1 Monomers & Polymers](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-1-1-monomers-and-polymers.md) - [1.1.2 Condensation & Hydrolysis Reactions](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-1-2-condensation-and-hydrolysis-reactions.md) - 1.2 Carbohydrates - [1.2.1 Structure of Carbohydrates](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-2-1-structure-of-carbohydrates.md) - [1.2.2 Types of Polysaccharides](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-2-2-types-of-polysaccharides.md) - [1.2.3 End of Topic Test - Monomers, Polymers and Carbs](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-2-3-end-of-topic-test-monomers-polymers-and-carbs.md) - [1.2.4 Exam-Style Question - Carbohydrates](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-2-4-exam-style-question-carbohydrates.md) - [1.2.5 A-A* (AO3/4) - Carbohydrates](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-2-5-a-a-ao34-carbohydrates.md) - 1.3 Lipids - [1.3.1 Triglycerides & Phospholipids](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-3-1-triglycerides-and-phospholipids.md) - [1.3.2 Types of Fatty Acids](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-3-2-types-of-fatty-acids.md) - [1.3.3 Testing for Lipids](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-3-3-testing-for-lipids.md) - [1.3.4 Exam-Style Question - Fats](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-3-4-exam-style-question-fats.md) - [1.3.5 A-A* (AO3/4) - Lipids](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-3-5-a-a-ao34-lipids.md) - 1.4 Proteins - [1.4.1 The Peptide Chain](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-4-1-the-peptide-chain.md) - [1.4.2 Investigating Proteins](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-4-2-investigating-proteins.md) - [1.4.3 Primary & Secondary Protein Structure](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-4-3-primary-and-secondary-protein-structure.md) - [1.4.4 Tertiary & Quaternary Protein Structure](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-4-4-tertiary-and-quaternary-protein-structure.md) - [1.4.5 Enzymes](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-4-5-enzymes.md) - [1.4.6 Factors Affecting Enzyme Activity](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-4-6-factors-affecting-enzyme-activity.md) - [1.4.7 Enzyme-Controlled Reactions](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-4-7-enzyme-controlled-reactions.md) - [1.4.8 End of Topic Test - Lipids & Proteins](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-4-8-end-of-topic-test-lipids-and-proteins.md) - [1.4.9 A-A* (AO3/4) - Enzymes](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-4-9-a-a-ao34-enzymes.md) - [1.4.10 A-A* (AO3/4) - Proteins](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-4-10-a-a-ao34-proteins.md) - [1.4.11 Diagnostic Misconceptions - Enzyme Inhibitors](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-4-11-diagnostic-misconceptions-enzyme-inhibitors.md) - 1.5 Nucleic Acids - [1.5.1 DNA & RNA](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-5-1-dna-and-rna.md) - [1.5.2 Nucleotides](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-5-2-nucleotides.md) - [1.5.3 Polynucleotides](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-5-3-polynucleotides.md) - [1.5.4 DNA Replication](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-5-4-dna-replication.md) - [1.5.5 Exam-Style Question - Nucleic Acids](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-5-5-exam-style-question-nucleic-acids.md) - [1.5.6 A-A* (AO3/4) - Nucleic Acids](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-5-6-a-a-ao34-nucleic-acids.md) - 1.6 ATP - [1.6.1 Structure of ATP](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-6-1-structure-of-atp.md) - [1.6.2 Hydrolysis of ATP](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-6-2-hydrolysis-of-atp.md) - [1.6.3 Resynthesis of ATP](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-6-3-resynthesis-of-atp.md) - [1.6.4 End of Topic Test - Nucleic Acids & ATP](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-6-4-end-of-topic-test-nucleic-acids-and-atp.md) - 1.7 Water - [1.7.1 Importance of Water](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-7-1-importance-of-water.md) - [1.7.2 Structure of Water](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-7-2-structure-of-water.md) - [1.7.3 Properties of Water](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-7-3-properties-of-water.md) - [1.7.4 A-A* (AO3/4) - Water](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-7-4-a-a-ao34-water.md) - 1.8 Inorganic Ions - [1.8.1 Inorganic Ions](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-8-1-inorganic-ions.md) - [1.8.2 End of Topic Test - Water & Inorganic Ions](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-8-2-end-of-topic-test-water-and-inorganic-ions.md) ### 2 Cells - 2.1 Cell Structure - [2.1.1 Introduction to Cells](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-1-1-introduction-to-cells.md) - [2.1.2 Eukaryotic Cells & Organelles](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-1-2-eukaryotic-cells-and-organelles.md) - [2.1.3 Eukaryotic Cells & Organelles 2](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-1-3-eukaryotic-cells-and-organelles-2.md) - [2.1.4 Prokaryotes](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-1-4-prokaryotes.md) - [2.1.5 A-A* (AO3/4) - Organelles](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-1-5-a-a-ao34-organelles.md) - [2.1.6 Methods of Studying Cells](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-1-6-methods-of-studying-cells.md) - [2.1.7 Microscopes](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-1-7-microscopes.md) - [2.1.8 End of Topic Test - Cell Structure](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-1-8-end-of-topic-test-cell-structure.md) - [2.1.9 Exam-Style Question - Cells](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-1-9-exam-style-question-cells.md) - [2.1.10 A-A* (AO3/4) - Cells](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-1-10-a-a-ao34-cells.md) - 2.2 Mitosis & Cancer - [2.2.1 Mitosis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-2-1-mitosis.md) - [2.2.2 Stages of Mitosis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-2-2-stages-of-mitosis.md) - [2.2.3 Investigating Mitosis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-2-3-investigating-mitosis.md) - [2.2.4 Cancer](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-2-4-cancer.md) - [2.2.5 A-A* (AO3/4) - The Cell Cycle](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-2-5-a-a-ao34-the-cell-cycle.md) - 2.3 Transport Across Cell Membrane - [2.3.1 Cell Membrane Structure](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-3-1-cell-membrane-structure.md) - [2.3.2 A-A* (AO3/4) - Membrane Structure](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-3-2-a-a-ao34-membrane-structure.md) - [2.3.3 Diffusion](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-3-3-diffusion.md) - [2.3.4 Osmosis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-3-4-osmosis.md) - [2.3.5 Active Transport](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-3-5-active-transport.md) - [2.3.6 End of Topic Test - Mitosis, Cancer & Transport](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-3-6-end-of-topic-test-mitosis-cancer-and-transport.md) - [2.3.7 Exam-Style Question - Membranes](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-3-7-exam-style-question-membranes.md) - [2.3.8 A-A* (AO3/4) - Membranes & Transport](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-3-8-a-a-ao34-membranes-and-transport.md) - [2.3.9 A-A*- Mitosis, Cancer & Transport](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-3-9-a-a-mitosis-cancer-and-transport.md) - 2.4 Cell Recognition & the Immune System - [2.4.1 Immune System](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-1-immune-system.md) - [2.4.2 Phagocytosis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-2-phagocytosis.md) - [2.4.3 T Lymphocytes](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-3-t-lymphocytes.md) - [2.4.4 B Lymphocytes](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-4-b-lymphocytes.md) - [2.4.5 Antibodies](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-5-antibodies.md) - [2.4.6 Primary & Secondary Response](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-6-primary-and-secondary-response.md) - [2.4.7 Vaccines](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-7-vaccines.md) - [2.4.8 HIV](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-8-hiv.md) - [2.4.9 Ethical Issues](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-9-ethical-issues.md) - [2.4.10 End of Topic Test - Immune System](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-10-end-of-topic-test-immune-system.md) - [2.4.11 Exam-Style Question - Immune System](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-11-exam-style-question-immune-system.md) - [2.4.12 A-A* (AO3/4) - Immune System](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-12-a-a-ao34-immune-system.md) - [2.4.13 Diagnostic Misconceptions - Humoral vs Cellular](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-13-diagnostic-misconceptions-humoral-vs-cellular.md) ### 3 Substance Exchange - 3.1 Surface Area to Volume Ratio - [3.1.1 Size & Surface Area](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-1-1-size-and-surface-area.md) - [3.1.2 A-A* (AO3/4) - Cell Size](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-1-2-a-a-ao34-cell-size.md) - 3.2 Gas Exchange - [3.2.1 Single-Celled Organisms](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-2-1-single-celled-organisms.md) - [3.2.2 Multicellular Organisms](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-2-2-multicellular-organisms.md) - [3.2.3 Control of Water Loss](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-2-3-control-of-water-loss.md) - [3.2.4 Human Gas Exchange](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-2-4-human-gas-exchange.md) - [3.2.5 Ventilation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-2-5-ventilation.md) - [3.2.6 Dissection](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-2-6-dissection.md) - [3.2.7 Measuring Gas Exchange](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-2-7-measuring-gas-exchange.md) - [3.2.8 Lung Disease](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-2-8-lung-disease.md) - [3.2.9 Lung Disease Data](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-2-9-lung-disease-data.md) - [3.2.10 End of Topic Test - Gas Exchange](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-2-10-end-of-topic-test-gas-exchange.md) - [3.2.11 A-A* (AO3/4) - Gas Exchange](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-2-11-a-a-ao34-gas-exchange.md) - 3.3 Digestion & Absorption - [3.3.1 Overview of Digestion](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-3-1-overview-of-digestion.md) - [3.3.2 Digestion in Mammals](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-3-2-digestion-in-mammals.md) - [3.3.3 Absorption](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-3-3-absorption.md) - [3.3.4 End of Topic Test - Substance Exchange & Digestion](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-3-4-end-of-topic-test-substance-exchange-and-digestion.md) - [3.3.5 A-A* (AO3/4) - Substance Ex & Digestion](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-3-5-a-a-ao34-substance-ex-and-digestion.md) - 3.4 Mass Transport - [3.4.1 Haemoglobin](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-1-haemoglobin.md) - [3.4.2 Oxygen Transport](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-2-oxygen-transport.md) - [3.4.3 The Circulatory System](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-3-the-circulatory-system.md) - [3.4.4 The Heart](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-4-the-heart.md) - [3.4.5 Blood Vessels](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-5-blood-vessels.md) - [3.4.6 Cardiovascular Disease](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-6-cardiovascular-disease.md) - [3.4.7 Heart Dissection](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-7-heart-dissection.md) - [3.4.8 Xylem](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-8-xylem.md) - [3.4.9 Phloem](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-9-phloem.md) - [3.4.10 Investigating Plant Transport](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-10-investigating-plant-transport.md) - [3.4.11 End of Topic Test - Mass Transport](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-11-end-of-topic-test-mass-transport.md) - [3.4.12 A-A* (AO3/4) - Mass Transport](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-12-a-a-ao34-mass-transport.md) - [3.4.13 Diagnostic Misconceptions - Concentration Gradient](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-13-diagnostic-misconceptions-concentration-gradient.md) - [3.4.14 Diagnostic Misconceptions - Cardiac Cycle](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-14-diagnostic-misconceptions-cardiac-cycle.md) - [3.4.15 Diagnostic Misconceptions - Carrying Capacity](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-15-diagnostic-misconceptions-carrying-capacity.md) - [3.4.16 Diagnostic Misconceptions - Translocation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-16-diagnostic-misconceptions-translocation.md) ### 4 Genetic Information & Variation - 4.1 DNA, Genes & Chromosomes - [4.1.1 DNA](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-1-1-dna.md) - [4.1.2 Genes](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-1-2-genes.md) - [4.1.3 Non-Coding Genes](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-1-3-non-coding-genes.md) - [4.1.4 The Genetic Code](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-1-4-the-genetic-code.md) - [4.1.5 A-A* (AO3/4) - DNA](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-1-5-a-a-ao34-dna.md) - 4.2 DNA & Protein Synthesis - [4.2.1 Protein Synthesis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-2-1-protein-synthesis.md) - [4.2.2 Transcription & Translation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-2-2-transcription-and-translation.md) - [4.2.3 End of Topic Test - DNA, Genes & Protein Synthesis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-2-3-end-of-topic-test-dna-genes-and-protein-synthesis.md) - [4.2.4 Exam-Style Question - Protein Synthesis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-2-4-exam-style-question-protein-synthesis.md) - [4.2.5 A-A* (AO3/4) - Coronavirus Translation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-2-5-a-a-ao34-coronavirus-translation.md) - [4.2.6 A-A* (AO3/4) - Transcription](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-2-6-a-a-ao34-transcription.md) - [4.2.7 A-A* (AO3/4) - Translation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-2-7-a-a-ao34-translation.md) - 4.3 Mutations & Meiosis - [4.3.1 Mutations](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-3-1-mutations.md) - [4.3.2 Meiosis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-3-2-meiosis.md) - [4.3.3 A-A* (AO3/4) - Meiosis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-3-3-a-a-ao34-meiosis.md) - [4.3.4 Meiosis vs Mitosis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-3-4-meiosis-vs-mitosis.md) - [4.3.5 End of Topic Test - Mutations, Meiosis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-3-5-end-of-topic-test-mutations-meiosis.md) - [4.3.6 A-A* (AO3/4) - DNA,Genes, CellDiv & ProtSynth](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-3-6-a-a-ao34-dnagenes-celldiv-and-protsynth.md) - [4.3.7 Diagnostic Misconceptions - Meiosis vs Mitosis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-3-7-diagnostic-misconceptions-meiosis-vs-mitosis.md) - 4.4 Genetic Diversity & Adaptation - [4.4.1 Genetic Diversity](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-4-1-genetic-diversity.md) - [4.4.2 Natural Selection](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-4-2-natural-selection.md) - [4.4.3 A-A* (AO3/4) - Natural Selection](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-4-3-a-a-ao34-natural-selection.md) - [4.4.4 Adaptations](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-4-4-adaptations.md) - [4.4.5 Investigating Natural Selection](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-4-5-investigating-natural-selection.md) - [4.4.6 End of Topic Test - Genetic Diversity & Adaptation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-4-6-end-of-topic-test-genetic-diversity-and-adaptation.md) - [4.4.7 A-A* (AO3/4) - Genetic Diversity & Adaptation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-4-7-a-a-ao34-genetic-diversity-and-adaptation.md) - 4.5 Species & Taxonomy - [4.5.1 Courtship Behaviour](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-5-1-courtship-behaviour.md) - [4.5.2 Phylogeny](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-5-2-phylogeny.md) - [4.5.3 Classification](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-5-3-classification.md) - [4.5.4 DNA Technology](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-5-4-dna-technology.md) - [4.5.5 A-A* (AO3/4) - Species & Taxonomy](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-5-5-a-a-ao34-species-and-taxonomy.md) - 4.6 Biodiversity Within a Community - [4.6.1 Biodiversity](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-6-1-biodiversity.md) - [4.6.2 Index of diversity](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-6-2-index-of-diversity.md) - [4.6.3 Agriculture](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-6-3-agriculture.md) - [4.6.4 End of Topic Test - Species,Taxonomy& Biodiversity](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-6-4-end-of-topic-test-speciestaxonomyand-biodiversity.md) - [4.6.5 A-A* (AO3/4) - Species,Taxon&Biodiversity](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-6-5-a-a-ao34-speciestaxonandbiodiversity.md) - 4.7 Investigating Diversity - [4.7.1 Genetic Diversity](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-7-1-genetic-diversity.md) - [4.7.2 Quantitative Investigation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-7-2-quantitative-investigation.md) ### 5 Energy Transfers (A2 only) - 5.1 Photosynthesis - [5.1.1 Overview of Photosynthesis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-1-1-overview-of-photosynthesis.md) - [5.1.2 Photoionisation of Chlorophyll](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-1-2-photoionisation-of-chlorophyll.md) - [5.1.3 Production of ATP & Reduced NADP](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-1-3-production-of-atp-and-reduced-nadp.md) - [5.1.4 Cyclic Photophosphorylation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-1-4-cyclic-photophosphorylation.md) - [5.1.5 Light-Independent Reaction](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-1-5-light-independent-reaction.md) - [5.1.6 A-A* (AO3/4) - Photosynthesis Reactions](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-1-6-a-a-ao34-photosynthesis-reactions.md) - [5.1.7 Limiting Factors](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-1-7-limiting-factors.md) - [5.1.8 Photosynthesis Experiments](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-1-8-photosynthesis-experiments.md) - [5.1.9 End of Topic Test - Photosynthesis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-1-9-end-of-topic-test-photosynthesis.md) - [5.1.10 A-A* (AO3/4) - Photosynthesis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-1-10-a-a-ao34-photosynthesis.md) - 5.2 Respiration - [5.2.1 Overview of Respiration](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-2-1-overview-of-respiration.md) - [5.2.2 Anaerobic Respiration](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-2-2-anaerobic-respiration.md) - [5.2.3 A-A* (AO3/4) - Anaerobic Respiration](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-2-3-a-a-ao34-anaerobic-respiration.md) - [5.2.4 The Link Reaction](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-2-4-the-link-reaction.md) - [5.2.5 The Krebs Cycle](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-2-5-the-krebs-cycle.md) - [5.2.6 Oxidative Phosphorylation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-2-6-oxidative-phosphorylation.md) - [5.2.7 Respiration Experiments](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-2-7-respiration-experiments.md) - [5.2.8 End of Topic Test - Respiration](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-2-8-end-of-topic-test-respiration.md) - [5.2.9 A-A* (AO3/4) - Respiration](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-2-9-a-a-ao34-respiration.md) - [5.2.10 Diagnostic Misconceptions - Aerobic vs Anaerobic](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-2-10-diagnostic-misconceptions-aerobic-vs-anaerobic.md) - 5.3 Energy & Ecosystems - [5.3.1 Biomass](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-3-1-biomass.md) - [5.3.2 Production & Productivity](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-3-2-production-and-productivity.md) - [5.3.3 Agricultural Practices](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-3-3-agricultural-practices.md) - 5.4 Nutrient Cycles - [5.4.1 Nitrogen Cycle](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-4-1-nitrogen-cycle.md) - [5.4.2 Phosphorous Cycle](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-4-2-phosphorous-cycle.md) - [5.4.3 Fertilisers & Eutrophication](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-4-3-fertilisers-and-eutrophication.md) - [5.4.4 End of Topic Test - Nutrient Cycles](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-4-4-end-of-topic-test-nutrient-cycles.md) - [5.4.5 A-A* (AO3/4) - Energy,Ecosystems&NutrientCycles](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-4-5-a-a-ao34-energyecosystemsandnutrientcycles.md) ### 6 Responding to Change (A2 only) - 6.1 Nervous Communication - [6.1.1 Survival](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-1-1-survival.md) - [6.1.2 Plant Responses](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-1-2-plant-responses.md) - [6.1.3 Animal Responses](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-1-3-animal-responses.md) - [6.1.4 Reflexes](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-1-4-reflexes.md) - [6.1.5 End of Topic Test - Reflexes, Responses & Survival](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-1-5-end-of-topic-test-reflexes-responses-and-survival.md) - [6.1.6 Receptors](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-1-6-receptors.md) - [6.1.7 The Human Retina](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-1-7-the-human-retina.md) - [6.1.8 Control of Heart Rate](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-1-8-control-of-heart-rate.md) - [6.1.9 End of Topic Test - Receptors, Retina & Heart Rate](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-1-9-end-of-topic-test-receptors-retina-and-heart-rate.md) - 6.2 Nervous Coordination - [6.2.1 Neurones](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-2-1-neurones.md) - [6.2.2 Action Potentials](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-2-2-action-potentials.md) - [6.2.3 Speed of Transmission](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-2-3-speed-of-transmission.md) - [6.2.4 End of Topic Test - Neurones & Action Potentials](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-2-4-end-of-topic-test-neurones-and-action-potentials.md) - [6.2.5 Synapses](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-2-5-synapses.md) - [6.2.6 Types of Synapse](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-2-6-types-of-synapse.md) - [6.2.7 Medical Application](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-2-7-medical-application.md) - [6.2.8 End of Topic Test - Synapses](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-2-8-end-of-topic-test-synapses.md) - [6.2.9 A-A* (AO3/4) - Nervous Comm&Coord](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-2-9-a-a-ao34-nervous-commandcoord.md) - 6.3 Muscle Contraction - [6.3.1 Skeletal Muscle](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-3-1-skeletal-muscle.md) - [6.3.2 Sliding Filament Theory](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-3-2-sliding-filament-theory.md) - [6.3.3 Contraction](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-3-3-contraction.md) - [6.3.4 Slow & Fast Twitch Fibres](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-3-4-slow-and-fast-twitch-fibres.md) - [6.3.5 End of Topic Test - Muscles](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-3-5-end-of-topic-test-muscles.md) - [6.3.6 A-A* (AO3/4) - Muscle Contraction](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-3-6-a-a-ao34-muscle-contraction.md) - 6.4 Homeostasis - [6.4.1 Overview of Homeostasis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-1-overview-of-homeostasis.md) - [6.4.2 Blood Glucose Concentration](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-2-blood-glucose-concentration.md) - [6.4.3 Controlling Blood Glucose Concentration](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-3-controlling-blood-glucose-concentration.md) - [6.4.4 End of Topic Test - Blood Glucose](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-4-end-of-topic-test-blood-glucose.md) - [6.4.5 Primary & Secondary Messengers](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-5-primary-and-secondary-messengers.md) - [6.4.6 Diabetes Mellitus](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-6-diabetes-mellitus.md) - [6.4.7 Measuring Glucose Concentration](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-7-measuring-glucose-concentration.md) - [6.4.8 Osmoregulation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-8-osmoregulation.md) - [6.4.9 Controlling Blood Water Potential](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-9-controlling-blood-water-potential.md) - [6.4.10 ADH](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-10-adh.md) - [6.4.11 End of Topic Test - Diabetes & Osmoregulation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-11-end-of-topic-test-diabetes-and-osmoregulation.md) - [6.4.12 A-A* (AO3/4) - Homeostasis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-12-a-a-ao34-homeostasis.md) - [6.4.13 Diagnostic Misconceptions - Effect of ADH](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-13-diagnostic-misconceptions-effect-of-adh.md) ### 7 Genetics & Ecosystems (A2 only) - 7.1 Genetics - [7.1.1 Key Terms in Genetics](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-1-1-key-terms-in-genetics.md) - [7.1.2 Inheritance](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-1-2-inheritance.md) - [7.1.3 Linkage](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-1-3-linkage.md) - [7.1.4 Multiple Alleles & Epistasis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-1-4-multiple-alleles-and-epistasis.md) - [7.1.5 Chi-Squared Test](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-1-5-chi-squared-test.md) - [7.1.6 End of Topic Test - Genetics](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-1-6-end-of-topic-test-genetics.md) - [7.1.7 A-A* (AO3/4) - Genetics](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-1-7-a-a-ao34-genetics.md) - [7.1.8 Diagnostic Misconceptions - Dihybrid Inheritance](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-1-8-diagnostic-misconceptions-dihybrid-inheritance.md) - [7.1.9 Diagnostic Misconceptions - Sex Linkage](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-1-9-diagnostic-misconceptions-sex-linkage.md) - 7.2 Populations - [7.2.1 Populations](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-2-1-populations.md) - [7.2.2 Hardy-Weinberg Principle](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-2-2-hardy-weinberg-principle.md) - 7.3 Evolution - [7.3.1 Variation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-3-1-variation.md) - [7.3.2 Natural Selection & Evolution](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-3-2-natural-selection-and-evolution.md) - [7.3.3 End of Topic Test - Populations & Evolution](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-3-3-end-of-topic-test-populations-and-evolution.md) - [7.3.4 Types of Selection](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-3-4-types-of-selection.md) - [7.3.5 Types of Selection Summary](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-3-5-types-of-selection-summary.md) - [7.3.6 Overview of Speciation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-3-6-overview-of-speciation.md) - [7.3.7 Causes of Speciation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-3-7-causes-of-speciation.md) - [7.3.8 Diversity](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-3-8-diversity.md) - [7.3.9 End of Topic Test - Selection & Speciation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-3-9-end-of-topic-test-selection-and-speciation.md) - [7.3.10 A-A* (AO3/4) - Populations & Evolution](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-3-10-a-a-ao34-populations-and-evolution.md) - [7.3.11 Diagnostic Misconceptions - Types of Speciation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-3-11-diagnostic-misconceptions-types-of-speciation.md) - 7.4 Populations in Ecosystems - [7.4.1 Overview of Ecosystems](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-4-1-overview-of-ecosystems.md) - [7.4.2 Niche](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-4-2-niche.md) - [7.4.3 Population Size](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-4-3-population-size.md) - [7.4.4 Investigating Population Size](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-4-4-investigating-population-size.md) - [7.4.5 End of Topic Test - Ecosystems & Population Size](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-4-5-end-of-topic-test-ecosystems-and-population-size.md) - [7.4.6 Succession](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-4-6-succession.md) - [7.4.7 Conservation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-4-7-conservation.md) - [7.4.8 End of Topic Test - Succession & Conservation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-4-8-end-of-topic-test-succession-and-conservation.md) - [7.4.9 A-A* (AO3/4) - Ecosystems](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-4-9-a-a-ao34-ecosystems.md) ### 8 The Control of Gene Expression (A2 only) - 8.1 Mutation - [8.1.1 Mutations](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-1-1-mutations.md) - [8.1.2 Effects of Mutations](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-1-2-effects-of-mutations.md) - [8.1.3 Causes of Mutations](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-1-3-causes-of-mutations.md) - [8.1.4 Diagnostic Misconceptions - Gene Expression](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-1-4-diagnostic-misconceptions-gene-expression.md) - 8.2 Gene Expression - [8.2.1 Stem Cells](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-1-stem-cells.md) - [8.2.2 Stem Cells in Disease](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-2-stem-cells-in-disease.md) - [8.2.3 End of Topic Test - Mutation & Gene Epression](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-3-end-of-topic-test-mutation-and-gene-epression.md) - [8.2.4 A-A* (AO3/4) - Mutation & Stem Cells](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-4-a-a-ao34-mutation-and-stem-cells.md) - [8.2.5 Regulating Transcription](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-5-regulating-transcription.md) - [8.2.6 Epigenetics](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-6-epigenetics.md) - [8.2.7 Epigenetics & Disease](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-7-epigenetics-and-disease.md) - [8.2.8 Regulating Translation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-8-regulating-translation.md) - [8.2.9 Experimental Data](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-9-experimental-data.md) - [8.2.10 End of Topic Test - Transcription & Translation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-10-end-of-topic-test-transcription-and-translation.md) - [8.2.11 Tumours](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-11-tumours.md) - [8.2.12 Correlations & Causes](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-12-correlations-and-causes.md) - [8.2.13 Prevention & Treatment](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-13-prevention-and-treatment.md) - [8.2.14 End of Topic Test - Cancer](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-14-end-of-topic-test-cancer.md) - [8.2.15 A-A* (AO3/4) - Gene Expression & Cancer](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-15-a-a-ao34-gene-expression-and-cancer.md) - 8.3 Genome Projects - [8.3.1 Using Genome Projects](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-3-1-using-genome-projects.md) - 8.4 Gene Technology - [8.4.1 Recombinant DNA](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-4-1-recombinant-dna.md) - [8.4.2 Producing Fragments](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-4-2-producing-fragments.md) - [8.4.3 Amplification](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-4-3-amplification.md) - [8.4.4 End of Topic Test - Genome Project & Amplification](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-4-4-end-of-topic-test-genome-project-and-amplification.md) - [8.4.5 Using Recombinant DNA](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-4-5-using-recombinant-dna.md) - [8.4.6 Medical Diagnosis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-4-6-medical-diagnosis.md) - [8.4.7 Genetic Fingerprinting](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-4-7-genetic-fingerprinting.md) - [8.4.8 End of Topic Test - Gene Technologies](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-4-8-end-of-topic-test-gene-technologies.md) - [8.4.9 A-A* (AO3/4) - Gene Technology](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-4-9-a-a-ao34-gene-technology.md) ### 9 Mathematical Skills - 9.1 Mathematical Skills - [9.1.1 Diagnostic Misconceptions - Converting Units](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/9-1-1-diagnostic-misconceptions-converting-units.md) - [9.1.2 Diagnostic Misconceptions - Correct Hypothesis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/9-1-2-diagnostic-misconceptions-correct-hypothesis.md) - [9.1.3 Diagnostic Misconceptions - Interpret Hypothesis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/9-1-3-diagnostic-misconceptions-interpret-hypothesis.md) - [9.1.4 Diagnostic Misconceptions - Calculate Uncertainty](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/9-1-4-diagnostic-misconceptions-calculate-uncertainty.md)