What does Unit B2 cover in CCEA Double Award Science?

Unit B2, Body Systems, Genetics, Microorganisms and Health, covers osmosis and plant transport, the circulatory system with blood, the heart and blood vessels, chromosomes, genes and DNA, cell division by mitosis and meiosis, monohybrid inheritance and sex determination, variation, natural selection and evolution, microorganisms and the immune system, and medicines, antibiotics and drugs.

How is Unit B2 assessed in the Double Award?

B2 is one of the externally marked written units of the GCSE Science Double Award (code 1370). It is sat at either Foundation or Higher tier and uses structured short-answer questions, data and calculation questions, and longer questions. With the other five written units and the Practical Skills unit it makes up the two GCSE grades of the Double Award.

What calculations and genetics work come up in Unit B2?

The main skills are Punnett squares for monohybrid crosses (reading ratios such as 3 to 1 and probabilities such as 25 percent), percentage change in mass in osmosis practicals, and interpreting data on variation, transpiration and heart rate. A calculator is allowed in the written papers.

Which practicals are linked to Unit B2?

Prescribed practicals linked to B2 include investigating osmosis using potato or other plant tissue and measuring percentage change in mass, and investigating the factors affecting transpiration. Microbiology work uses aseptic technique. These feed into the Practical Skills unit.

How should I revise Unit B2?

Learn the definitions in genetics precisely, then practise Punnett squares until the ratios are automatic. Master osmosis as the key transport idea and link every blood vessel and chamber to its pressure. Learn natural selection as an ordered sequence, and the immune response and vaccination step by step, then practise CCEA past-paper questions and the calculations.

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CCEA GCSE Double Award Science: B2 Body Systems, Genetics, Microorganisms and Health overview

An overview of Biology Unit B2 (Body Systems, Genetics, Microorganisms and Health) of CCEA GCSE Double Award Science, mapping osmosis and plant transport, the circulatory system, DNA and genetics, cell division, inheritance, variation and evolution, and microorganisms and health.

Generated by Claude Opus 4.87 min readCCEA 1370 Unit B2Updated 2026-06-15

Reviewed by: AI editorial process; not yet individually human-reviewed

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What this unit covers
How it is examined
How to study it

Unit B2 of CCEA GCSE Double Award Science is the second Biology unit. It moves from transport in plants and animals to genetics, inheritance, evolution and health, and is examined on the B2 written paper at Foundation or Higher tier. This page maps the topics and links to a focused answer page for each one.

What this unit covers

Osmosis and plant transport: Osmosis across a partially permeable membrane, turgid and flaccid cells, xylem and phloem, root hair cells and transpiration. See Osmosis and plant transport.
The circulatory system, blood and the heart: The components of blood, the heart and double circulation, and the adaptations of arteries, veins and capillaries. See The circulatory system, blood and the heart.
Chromosomes, genes and DNA: The nucleus, chromosomes, genes and DNA, the double helix and base pairs, and how a gene codes for a protein. See Chromosomes, genes and DNA.
Mitosis and meiosis: Mitosis for growth and repair, meiosis for gametes, and why meiosis creates variation. See Mitosis and meiosis.
Monohybrid inheritance and sex determination: The genetics terms, Punnett squares, sex determination, and inheriting a recessive disorder. See Monohybrid inheritance and sex determination.
Variation, natural selection and evolution: Continuous and discontinuous variation, mutation, natural selection, antibiotic resistance and fossils. See Variation, natural selection and evolution.
Microorganisms, defence and the immune system: Types of microorganism, pathogens, defences, white blood cells and vaccination. See Microorganisms, defence and the immune system.
Medicines, antibiotics and drugs: How antibiotics work, resistance, testing medicines, and the effects of alcohol and tobacco. See Medicines, antibiotics and drugs.

How it is examined

B2 is one written unit of the Double Award, sat at the same tier as the other units. Expect structured questions on osmosis, blood vessels and the heart, DNA, Punnett squares, natural selection and the immune response, plus a longer answer such as explaining antibiotic resistance. A calculator is allowed.

How to study it

Master osmosis first as the key transport idea, then link every blood vessel and chamber to its pressure. Get the genetics definitions exact and drill Punnett squares. Learn natural selection and the immune response as ordered sequences. Then practise CCEA past papers and finish with the module quiz.

Sources & how we know this

CCEA GCSE Science Double Award specification — CCEA (2017)