OCR Gateway GCSE Combined Science A Biology: organisms and ecosystems (B3 to B6) overview
An overview of the organism level systems, community level systems, genes and inheritance, and global challenges content (topics B3 to B6) in OCR Gateway GCSE Combined Science A (J250), mapping the nervous and hormonal systems, ecosystems and cycles, genetics, evolution and disease, and how they are examined.
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The later biology topics of OCR Gateway GCSE Combined Science A (specification J250) move from how an organism coordinates itself, out to whole ecosystems, inheritance and global health. B3 Organism level systems, B4 Community level systems, B5 Genes inheritance and selection and B6 Global challenges are examined across Biology Paper 1 (B3) and Biology Paper 2 (B4 to B6). This page maps the topics and links to a focused answer page for each.
The organisms and ecosystems topics
- Nervous system and homeostasis (B3)
- The central nervous system, the reflex arc and synapses, receptors and effectors, and homeostasis by negative feedback controlling temperature, glucose and water. See Nervous system and homeostasis.
- Hormonal coordination (B3)
- The endocrine system, control of blood glucose by insulin and glucagon, diabetes, the reproductive hormones and the menstrual cycle, and a comparison of nervous and hormonal control. See Hormonal coordination.
- Ecosystems and cycles (B4)
- Levels of organisation, biotic and abiotic factors, interdependence and competition, the carbon and nitrogen cycles, decomposition and biodiversity. See Ecosystems and cycles.
- Genetics and inheritance (B5)
- DNA, genes and chromosomes, sexual and asexual reproduction, meiosis, alleles, genotype and phenotype, Punnett squares and inherited disorders. See Genetics and inheritance.
- Variation and evolution (B5)
- Genetic and environmental variation, mutation, evolution by natural selection, evidence, selective breeding and genetic engineering. See Variation and evolution.
- Health and disease (B6)
- Communicable and non-communicable disease, pathogens, the immune system, vaccination, antibiotics and drug development. See Health and disease.
How these topics are examined
Topic B3 is assessed on Biology Paper 1, and topics B4 to B6 on Biology Paper 2; each paper is 1 hour 10 minutes, worth 60 marks and one sixth of the overall grade. Paper 2 assumes knowledge of B1 to B3. Questions include multiple choice, structured answers, genetic crosses and six-mark extended responses. Every paper also tests CS7 practical skills, so practicals such as investigating the effect of factors on a community can be examined.
How to study the organisms and ecosystems topics
- Work from the specification statements. Each point is a checklist; questions are written from them.
- Learn the sequences exactly. The reflex arc, the negative feedback examples, and the carbon and nitrogen cycles are marked on precise wording.
- Drill the genetics maths. Punnett squares and phenotype and genotype ratios appear in most Paper 2 sittings.
- Rehearse the big explanations. Natural selection, vaccination and drug testing are common six-mark questions.
- Practise past papers. Match your answers to the OCR command words such as Explain, Describe and Compare.
For the official specification
OCR publishes the full specification, past papers and mark schemes at ocr.org.uk. Always revise from the current specification and OCR's own past papers, because question style is board-specific.