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
Interdependence, competition and trophic levels
- 3 things to know
- Paper 4
Overview
What 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.
What you need to know
Answer each one before you reveal it.
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Key term
What is predation?
Key term
What is mutualism?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is meant by interdependence in a community?
Model answer
The species in the community rely on one another for things such as food, shelter, pollination and seed dispersal.
- 2
Explain why the loss of one species can change a whole community.
Model answer
Other species depend on it, so those that ate it or relied on it for shelter or pollination are affected, and their numbers change in turn.
- 3
What is predation?
Model answer
One organism, the predator, hunts and eats another organism, the prey.
- 4
What is mutualism?
Model answer
A close relationship between two species in which both of them benefit.
- 5
Give an example of mutualism and say how each partner benefits.
Model answer
A bee takes nectar from a flower as food and carries pollen between plants, so the bee is fed and the plant is pollinated.
- 6
What is parasitism?
Model answer
A relationship in which a parasite lives on or in a host, gaining from it while harming the host.
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