Key term
OCR GCSE Biology A J247
Cell Level Systems
Topic overviewMicroscopy, and sub-cellular structuresDNA structure: polymer, double helix and nucleotidesProtein synthesis and the triplet codeEnzyme action, and investigating enzymesCellular respiration as an exothermic processAerobic and anaerobic respiration comparedSynthesis and breakdown of carbohydrates, proteins and lipidsPhotosynthesis: producers and the processPhotosynthesis as endothermic, and investigating itLimiting factors in photosynthesis
Community Level Systems
Genes, Inheritance and Selection
Topic overviewGenetic terms, and the genomeGenome, environment and mutationsHow genetic variants influence phenotypeAsexual and sexual reproduction comparedHaploid, diploid and meiosisSingle gene inheritance and Punnett squaresSex determination, multiple genes and Mendel's workVariation within a population, and classificationNatural selection and evolutionEvidence for evolution, and the work of Darwin and Wallace
Global Challenges
Topic overviewField investigations, and human impact on ecosystemsMaintaining biodiversity, and evidence for environmental changeFood security, agricultural and biotechnological solutionsSelective breeding and genetic engineeringHealth, disease, and types of diseaseInteractions between diseases, and how they spreadReducing the spread of disease, and named examplesPhysical and chemical plant defencesDetecting plant disease; white blood cells and plateletsNon-specific defences and the immune systemMonoclonal antibodies and their usesVaccines, medicines and aseptic techniqueDeveloping new medicines, and non-communicable diseaseTreating cardiovascular disease, and lifestyle factorsCancer, and the use of stem cells in medicineGene technology in medicine, and the human genome
Organism Level Systems
Topic overviewThe nervous system and coordinated responsesThe reflex arcThe eye and its common defectsThe structure and function of the brainInvestigating and treating the brainHormonal coordination, thyroxine and adrenalineHormones in reproduction and the menstrual cycleContraception and treating infertilityPlant hormones and their commercial usesHomeostasis, and the skin in temperature controlInsulin and glucagon in blood sugar controlType 1 and type 2 diabetesOsmotic changes in body fluids, and the kidneysThe kidney tubule and the effect of ADHResponding to temperature and osmotic challenges
Scaling Up
Topic overviewDiffusion, osmosis and active transportMitosis, the cell cycle and cell differentiationStem cells in animals and meristems in plantsSurface area to volume ratio and exchange surfacesThe circulatory system, the heart and blood vesselsRed blood cells and plasmaRoot hair cells, transpiration and translocationXylem and phloemFactors affecting water uptake, and the potometer
Community Level Systems
- 5 subtopics
- 15 things to know
- Paper 4
What Community Level Systems covers
Community Level Systems is examined in Biology A Paper 4. It covers cycling materials and the role of microorganisms; the carbon and water cycles and decomposition; levels of organisation and abiotic and biotic factors; interdependence, competition and trophic levels; and pyramids of biomass and the efficiency of transfer.
Where it is assessed
Paper 4
Biology A Paper 4: 1 hour 45 minutes, 90 marks, 50% of the GCSE.
Check the OCR specification ↗The 5 subtopics
Each one has its own page.
- Cycling materials, and the role of microorganismsWhat it means for a material to cycle, carbon, nitrogen and water as cycled materials and why they must be recycled, the abiotic and biotic components of an ecosystem, bacteria and fungi as decomposers, how extracellular digestion and respiration release nutrients and carbon dioxide, why decomposers matter for soil minerals and nitrogen, and calculating mass loss and decay rate in a leaf bag investigation.Open →
- The carbon and water cycles, and decompositionHow photosynthesis removes carbon dioxide and respiration, combustion and decomposers return it, how water evaporates, transpires, condenses and falls as fresh rain, why the carbon and water cycles matter to organisms and habitats, what aerobic and anaerobic mean, how temperature, water and oxygen affect the rate of decomposition, turning a compost heap, and calculating rates of decay.Open →
- Levels of organisation, and abiotic and biotic factorsThe levels of organisation from individual organism to population, community and ecosystem, what a habitat is, the difference between abiotic and biotic factors, how temperature, light intensity, soil pH and moisture affect where plants grow and which species live in a habitat, and how predators and food shortage act on populations.Open →
- Interdependence, competition and trophic levelsWhat interdependence is and why losing one species changes a community, predation, mutualism and parasitism with examples such as bees and tapeworms, what plants and animals compete for, trophic levels, producers and primary, secondary and tertiary consumers, placing organisms in a food chain, and apex predators.Open →
- Pyramids of biomass and the efficiency of transferWhat biomass is, what a pyramid of biomass shows, why biomass is lost through egestion, excretion and respiration, calculating the efficiency of a transfer, and why food chains stay short.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Explain how temperature, light intensity and a fall in moisture each affect which plants or species live in a habitat.
Key term
Define population, community and ecosystem in that order, from the smallest level of organisation to the largest.
Key term
Explain why a pyramid of biomass is widest at the bottom.
Key term
Name two elements that are cycled between the living and non-living parts of an ecosystem.
Key term
What is meant by interdependence in a community?
Key term
What are the abiotic components of an ecosystem?
Process
Which process removes carbon dioxide from the air in the carbon cycle?
Key term
What is predation?
Key term
What is biomass?
Key term
What are the biotic components of an ecosystem?
Process
Name two processes that return carbon dioxide to the air in the carbon cycle.
Key term
List the levels of organisation in an ecosystem, from the smallest to the largest.
Key term
What is mutualism?
Key term
What does a pyramid of biomass show?
Take Community Level Systems further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Population vs Community
Population: all the organisms of one species in a habitat at one time. Community: all the different species living together in one habitat.
Abiotic factor vs Biotic factor
Abiotic factor: non-living condition of the environment affecting organisms. Biotic factor: influence on organisms that arises from other living organisms.
Egestion vs Excretion
Egestion: passing out of undigested food as faeces. Excretion: removal of waste products made in the body, such as urea.
Questions from this topic
Each one with the model answer underneath.
- 1
What is meant by saying that a material cycles through an ecosystem?
Model answer
It moves repeatedly between the living organisms and their non-living surroundings, being used and then returned rather than used up.
- 2
Name two elements that are cycled between the living and non-living parts of an ecosystem.
Model answer
Carbon and nitrogen.
- 3
What are the abiotic components of an ecosystem?
Model answer
The non-living parts, such as the air, water, soil and rock.
- 4
What are the biotic components of an ecosystem?
Model answer
The living organisms, such as plants, animals, fungi and bacteria.
- 5
Which cycled element do organisms need in order to make proteins?
Model answer
Nitrogen.
- 6
Which cycled element forms the framework of carbohydrates, lipids and proteins in living things?
Model answer
Carbon.
What is inside Levo
Six ways to work the same material.
Community Level Systems revision questions
- What does Community Level Systems cover in OCR GCSE Biology A?
- 5 subtopics: cycling materials, and the role of microorganisms, the carbon and water cycles, and decomposition, levels of organisation, and abiotic and biotic factors, interdependence, competition and trophic levels and pyramids of biomass and the efficiency of transfer. Each one has its own page with questions and model answers.
- How is Community Level Systems organised?
- By the OCR J247 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Community Level Systems, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
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