Process
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
Topic overviewThe nervous system and coordinated responsesThe reflex arcHormonal coordination, thyroxine and adrenalineHormones in reproduction and the menstrual cycleContraception and treating infertilityHomeostasis and control systems in the bodyInsulin and glucagon in blood sugar controlType 1 and type 2 diabetes
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
The carbon and water cycles, and decomposition
- 3 things to know
- Paper 8 (Biology)
Overview
How photosynthesis removes carbon dioxide from the air and respiration, combustion and decomposers return it, how water enters the atmosphere by evaporation and transpiration, condenses and falls as precipitation, why the water cycle supplies land organisms with fresh water, and why the carbon and water cycles matter to living organisms and their habitats.
What you need to know
Answer each one before you reveal it.
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Process
Name two processes that return carbon dioxide to the air in the carbon cycle.
Key term
Describe how the carbon in a dead animal returns to the air.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Which process removes carbon dioxide from the air in the carbon cycle?
Model answer
Photosynthesis by plants and algae.
- 2
Name two processes that return carbon dioxide to the air in the carbon cycle.
Model answer
Respiration by living organisms and the combustion of fuels.
- 3
Describe how the carbon in a dead animal returns to the air.
Model answer
Decomposers feed on the remains and release carbon dioxide as they respire.
- 4
Describe the two ways water enters the atmosphere in the water cycle.
Model answer
It evaporates from oceans, lakes and soil, and it is lost from plant leaves by transpiration.
- 5
What happens to water vapour as it rises and cools in the water cycle?
Model answer
It condenses into droplets that form clouds, and the water later falls as precipitation.
- 6
Explain why the water cycle provides land organisms with fresh water.
Model answer
Evaporation leaves dissolved salts behind, so the water that condenses and falls as rain is fresh and can be used by organisms on land.
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