AQA GCSE Biology Revision
GCSE Biology · Specification 8461 · England
Revising for AQA GCSE Biology? Below is every topic in the course, in specification order, with a short summary. Sign up free to get the full notes, quizzes, flashcards and exam questions for each one — filtered to the AQA course so you only revise what's on your exam.
AQA GCSE Biology topics
4.1 Cell biology →
Animal and plant cells are eukaryotic: their genetic material is enclosed in a nucleus. Bacterial cells are prokaryotic: they are much smaller, have no nucleus, and their DNA is a single loop, sometimes with extra small rings called plasmids.
4.2 Organisation →
Multicellular organisms are organised into a hierarchical structure. Cells are the basic building blocks. Similar cells group together to form tissues, which are groups of specialised cells working together to perform a specific function (e.g., muscle tissue). Different tissues then combine to form organs, which have a distinct structure and perform a specific role (e.g., the stomach). Finally, several organs working together form an organ system, such as the digestive system, which carries out a major bodily function.
4.3 Infection and response →
Pathogens are microorganisms that cause infectious diseases. The four main types are bacteria, viruses, fungi, and protists. Bacteria are single-celled organisms that can reproduce rapidly inside the body, producing toxins that damage cells and tissues. Viruses are much smaller, reproduce inside host cells, and cause cell damage. Fungi can be single-celled or multicellular. Protists are single-celled eukaryotes, often transferred by a vector like a mosquito.
4.4 Bioenergetics →
Photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy, stored in glucose. This vital process uses carbon dioxide from the atmosphere and water absorbed by roots. It occurs primarily in the chloroplasts of plant cells, which contain chlorophyll – a green pigment that absorbs light energy. Oxygen is produced as a waste product and released into the atmosphere, essential for most life forms on Earth. Understanding the inputs and outputs is crucial.
4.5 Homeostasis and response →
Homeostasis is the maintenance of a constant internal environment in the body, despite changes in the external surroundings. This process is crucial for optimal cell function and survival. Key factors regulated include body temperature, blood glucose levels, and water balance. Maintaining stable conditions ensures enzymes work efficiently and metabolic processes can occur effectively. Control systems involve receptors, coordination centres, and effectors working together to detect changes and bring about responses, often through negative feedback loops.
4.6 Inheritance, variation and evolution →
Inheritance is the passing of genetic information from one generation to the next. Chromosomes, found in the nucleus of eukaryotic cells, carry genetic material. Each chromosome is a long molecule of DNA, coiled up. Genes are small sections of DNA on a chromosome that code for a specific sequence of amino acids, which in turn form a specific protein. These proteins determine an organism's characteristics. Humans have 23 pairs of chromosomes, 22 autosomal pairs and one pair of sex chromosomes (XX for female, XY for male).
4.7 Ecology →
An ecosystem is the interaction of a community of living organisms (biotic factors) with the non-living parts of their environment (abiotic factors). Examples of biotic factors include plants, animals, and microorganisms. Abiotic factors include light intensity, temperature, moisture levels, and soil pH. All organisms in an ecosystem are interdependent; a change in one population can affect others. For instance, a decrease in predator numbers might lead to an increase in prey, which could then overgraze plants, impacting the entire food web.
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Topic summaries are ScienceForge originals, not official AQA material. Check the official AQA specification for the definitive content list.