Revision library

Topic-by-topic revision notes for UK GCSE and A-Level Science. 55 published spec points across 5 exam-board specifications. Each page includes the verbatim spec wording, mark-scheme phrasing, worked examples and a free try-it-yourself question.

AQA A-Level Biology (7402)

3.1.4 Proteins and Enzymes — Proteins are polymers of amino acids joined by peptide bonds. Their three-dimensional shape — set by the sequence of amino acids — determines what each protein does. Enzymes are a class of protein tha

AQA GCSE Biology (8461)

4.1.1 Cell structure — Cells are the smallest unit of life. This page covers everything in AQA GCSE Biology 4.1.1: the structures inside animal and plant cells, the differences between eukaryotic and prokaryotic cells (bact
4.1.2 Cell division — Cell division is how a single fertilised egg becomes a whole organism, how cuts heal, and how cancer goes wrong. This page covers AQA GCSE Biology 4.1.2: chromosomes, the cell cycle, the stages of mit
4.1.3 Transport in cells — Cells need to get materials in (oxygen, glucose, mineral ions, water) and get waste out (CO₂, urea). This page covers AQA GCSE Biology 4.1.3: the three transport processes — diffusion, osmosis and act
4.2.1 Principles of organisation — This page covers AQA GCSE Biology 4.2.1: the four levels of organisation that build a multicellular body — cell → tissue → organ → organ system. Knowing the precise definition of each level (and being
4.2.2 Animal tissues, organs and organ systems — Module 4.2.2 is the biggest topic in AQA GCSE Biology — it covers the digestive system (enzymes, food tests), the heart + blood vessels + blood + the double circulatory system, the lungs, and the conn
4.2.3 Plant tissues, organs and systems — This page covers AQA GCSE Biology 4.2.3: plant tissues (epidermis, palisade + spongy mesophyll, xylem, phloem, meristem), the leaf as an organ, and transpiration + translocation as the two main transp
4.3.1 Communicable diseases — Communicable diseases is a huge GCSE topic — it covers the four types of pathogen, how they spread, the body's three lines of defence, vaccination, antibiotics, and drug development. This page works t
4.3.2 Monoclonal antibodies (Bio only) — Monoclonal antibodies are the bit of GCSE Biology where 'specific shape' really earns its keep. They're identical antibodies made from a single clone of cells, all binding the same antigen — so you ca
4.3.3 Plant disease (Bio only) — Plant disease (4.3.3) is the Biology-only follow-up to communicable diseases. It covers two big ideas: plants get infected by pathogens (viral, bacterial, fungal) AND suffer when they lack mineral ion
4.4.1 Photosynthesis — Photosynthesis is the reaction that lets plants and algae build their own food from carbon dioxide and water, using light energy absorbed by chlorophyll inside chloroplasts. This page covers the word
4.4.2 Respiration — Respiration is the chemical reaction that releases energy from glucose in every living cell — it is NOT breathing. This page works through the three GCSE pathways (aerobic, anaerobic in muscles, anaer
4.5.1 Homeostasis — Homeostasis is the single biggest idea in human biology — and AQA 8461 topic 4.5.1 is where the rules are stated. You need to be able to define homeostasis, explain WHY it matters (enzymes, cells, res
4.5.2 The human nervous system — Your nervous system is the fast, electrical control system of your body. Where hormones drift slowly through the blood, nerve impulses race along neurones in milliseconds — which is why you snatch you
4.5.3 Hormonal coordination in humans — Your endocrine system is the body's slow, chemical communication network. Instead of using electrical impulses like the nervous system, it sends hormones — chemical messengers — through the bloodstrea
4.5.4 Plant hormones (Bio only) — Plants cannot run, but they can still respond to the world by growing in the right direction. Topic 4.5.4 of AQA 8461 is about the chemical messengers — plant hormones — that make this happen. You nee
4.6.1 Reproduction — Reproduction is the topic where AQA tests whether you understand the difference between making a copy of yourself and making a new genetically unique individual. Sexual reproduction needs two parents,
4.6.2 Variation and evolution — Variation and evolution is the heart of GCSE Biology. AQA 4.6.2 wants you to explain where variation comes from (genes, environment, or both), what mutations are and what they do, how natural selectio
4.6.3 The development of understanding of genetics and evolution — AQA 4.6.3 is a history-of-science topic. You need to explain WHY Darwin's theory of evolution by natural selection was only accepted slowly, what Mendel actually did with his peas and why his work was
4.6.4 Classification of living organisms — Classification is the part of GCSE Biology where you learn how scientists put millions of species into a tidy nested order, why that order changed when DNA evidence arrived, and why scientists call hu
4.7.1 Adaptations, interdependence and competition — Adaptations, interdependence and competition is the AQA topic that asks one big question: why do organisms live where they live, and what happens when they have to share that space with others? Every
4.7.2 Organisation of an ecosystem — Organisation of an ecosystem ties together every food-related idea you've already met — photosynthesis, respiration, feeding relationships, decomposition — and asks you to think about how they fit tog
4.7.3 Biodiversity and the effect of human interaction on ecosystems — Biodiversity is shrinking. Every habitat AQA asks you about — rainforests, peat bogs, rivers, grasslands — is being damaged by the same handful of human pressures: deforestation, peat extraction, wate
4.7.4 Trophic levels in an ecosystem (Bio only) — Trophic levels are the 'rungs of the ladder' in a food chain — and the central GCSE story is that the ladder gets thin very quickly. This page nails down what each level is called (producers, primary,
4.7.5 Food production (Bio only) — Food production is the engine that keeps eight billion people fed — but it sits on a knife edge. A growing population, changing diets, new pests, droughts and rising input costs all threaten food secu

Edexcel GCSE Biology (1BI0)

1.1 Cell biology — Cells are the basic unit of life. This page covers everything in Edexcel GCSE Biology (1BI0) Topic 1.1 Cell biology: the sub-cellular structures of eukaryotic and prokaryotic cells, the additional org
1.2 Levels of organisation — This page covers Edexcel GCSE Biology (1BI0) topic 1.2 — Levels of organisation. Edexcel asks you to climb the hierarchy in order: cells are the smallest unit of life, similar cells grouped together f
1.5 Transport in cells — Edexcel GCSE Biology 1BI0 topic 1.5 covers the three ways substances move into and out of cells — diffusion, osmosis and active transport — and the surface area to volume ratio that decides whether di
2.1 Mitosis and the cell cycle — Edexcel GCSE Biology 2.1 is all about mitosis and the cell cycle — how one parent cell becomes two genetically identical daughter cells, and what happens when the controls on that process break down.
2.2 Cell differentiation, growth and stem cells — Edexcel GCSE Biology 2.2 separates out the topic that AQA bolts onto cell division: differentiation and stem cells. The cell cycle and mitosis are already covered in 2.1 — here you focus on what cells
2.3 The nervous system — Edexcel 1BI0 topic 2.3 is the fast, electrical control system of the body. Where hormones drift slowly through the blood, nerve impulses race along neurones in milliseconds — which is why you snatch y
4.1 Evolution by natural selection — Edexcel 1BI0 4.1 strips evolution down to a single, examinable mechanism: natural selection. You don't need selective breeding here (that's covered in 4.3) and you don't need the full history of varia
5.2 Pathogens and immunity — Edexcel 1BI0 topic 5.2 is the immunity topic — and Edexcel marks it differently from other boards. The emphasis is sharp: **B-lymphocytes**, **antigen-antibody specificity** (complementary shapes), an
6.1 Photosynthesis — This page covers Edexcel GCSE Biology (1BI0) topic 6.1 Photosynthesis. You will revise the word and symbol equations, where photosynthesis happens (chloroplasts containing chlorophyll), and why the re
6.2 Transport in plants — This page covers Edexcel GCSE Biology (1BI0) topic 6.2: transport in plants. Edexcel narrows the lens onto the two transport tissues (xylem and phloem), water uptake at root hair cells, the transpirat
6.3 Plant hormones — Plants cannot move, but they grow in directions that help them survive. Topic 6.3 of Edexcel 1BI0 is about the plant hormones that control this growth — auxins, gibberellins and ethene — and how growe
7.1 Hormonal coordination — Edexcel 1BI0 topic 7.1 frames hormonal coordination as the body's slow, chemical communication system. Hormones — chemical messengers secreted by endocrine glands — travel in the bloodstream to target
7.2 Homeostasis — Homeostasis is one of the central ideas in Edexcel GCSE Biology (1BI0) — topic 7.2 sits inside the 'Animal coordination, control and homeostasis' section of Paper 2. You need to define homeostasis as
9.1 Ecosystems — Edexcel 9.1 Ecosystems brings together everything you've already learned about photosynthesis, respiration and feeding relationships and asks how organisms interact with each other and with their envi

OCR A-Level Biology A (H420)

2.1 Cell structure — Cell biology is where you meet the actual building blocks of every organism on the planet — and the OCR examiners reward students who use precise, technical language about them. This chapter covers th

OCR GCSE Biology A: Gateway Science (J247)

B1.1 Cell structures — Cells are the smallest unit of life. This page covers everything in OCR Gateway Science GCSE Biology A (J247) topic B1.1 Cell structures: the structures inside animal and plant cells, the differences
B1.2 What happens in cells (and what do cells need) — OCR B1.2 is the synthesis topic that links everything happening inside a cell: where its food comes from (photosynthesis), how it releases energy from that food (aerobic and anaerobic respiration), an
B1.3 Respiration — Respiration is the chemical reaction that releases energy from glucose in every living cell — it is NOT breathing. This OCR Gateway Science Biology A (J247) page covers section B1.3 in full: the three
B1.4 Photosynthesis — Photosynthesis is the reaction that lets green plants and algae build their own food from carbon dioxide and water, using light energy absorbed by chlorophyll inside chloroplasts. This page is mapped
B2.1 Supplying the cell — OCR Gateway B2.1 'Supplying the cell' ties together how substances enter and leave cells with the specialised cells that carry them. You need diffusion, osmosis and active transport (the three transpo
B2.2 The challenges of size — OCR Gateway B2.2 'The challenges of size' is the WHY behind every transport topic in GCSE Biology. A bacterium can survive on diffusion alone, but a whale or an oak tree cannot — the maths of surface
B3.1 Coordination and control — the nervous system — Your nervous system is the fast, electrical control system of your body. Where hormones drift slowly through the blood, nerve impulses race along neurones in milliseconds — which is why you snatch you
B3.2 Coordination and control — the endocrine system — Your endocrine system is the body's slow, chemical communication network. Instead of using electrical impulses like the nervous system, it sends hormones — chemical messengers — through the bloodstrea
B3.3 Maintaining internal environments — Homeostasis is the single biggest idea in human biology — and OCR Gateway Science Biology A (J247) topic B3.3 is where the rules are stated. You need to be able to define homeostasis, explain WHY it m
B4.1 Ecosystems — OCR J247 B4.1 Ecosystems brings together everything you have already met about photosynthesis, respiration, feeding relationships and microorganisms, and asks you to think about how the living and non
B5.1 Inheritance — OCR J247 B5.1 is the topic that tests whether you can move fluently between five linked ideas — gene, allele, genotype, phenotype, and Punnett square — and use them to predict the outcomes of a monohy
B5.2 Natural selection and evolution — OCR Gateway Science Biology A (J247) topic B5.2 ties natural selection to a small set of classic examples — pebble crabs picked off by gulls, peppered moths on sooty bark, antibiotic-resistant bacteri
B6.1 Monitoring and maintaining the environment — OCR Gateway B6.1 asks two big questions: how do we measure what's out there, and how do we keep it alive? You need to handle the maths of capture-recapture for mobile animals (the N = MC/R formula), e
B6.2 Feeding the human race — OCR Gateway B6.2 'Feeding the human race' asks how we feed a growing global population without wrecking the soils, waterways, pollinators and fish stocks we depend on. The spec lines up a toolkit: fer
B6.3 Monitoring and maintaining health — OCR Gateway B6.3 'Monitoring and maintaining health' is the OCR J247 equivalent of communicable diseases. It pulls together pathogens (bacteria, viruses, fungi, protists), the body's physical and immu