Key term
OCR GCSE Combined Science Biology J250
Cell Level Systems
Topic overviewMicroscopy, and sub-cellular structuresDNA structure: polymer, double helix and nucleotidesEnzyme 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 mutationsHaploid, diploid and meiosisSingle gene inheritance and Punnett squaresSex determination and characteristics controlled by many genesVariation within a population, and classificationNatural selection and evolutionEvidence for evolution from fossils and antibiotic resistance
Global Challenges
Topic overviewField investigations, and human impact on ecosystemsMaintaining biodiversity, monitoring conservation and ecotourismSelective breeding and genetic engineeringHealth, disease, and types of diseaseInteractions between diseases, and how they spreadReducing the spread of disease, and named examplesWhite blood cells, antibodies and plateletsNon-specific defences and the immune systemVaccines, 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
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
Cycling materials, and the role of microorganisms
- 3 things to know
- Paper 2 (Biology)
Overview
What 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.
What you need to know
Answer each one before you reveal it.
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Key term
What are the abiotic components of an ecosystem?
Key term
What are the biotic components of an ecosystem?
Questions from this subtopic
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.
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