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
- 4 subtopics
- 12 things to know
- Paper 2 (Biology)
What Community Level Systems covers
Community Level Systems is examined in Paper 2 (Biology). It covers cycling materials and the role of microorganisms; the carbon and water cycles; levels of organisation and abiotic and biotic factors; and interdependence and competition.
Where it is assessed
Paper 2 (Biology)
Combined Science A, Paper 2 (Biology): 1 hour 10 minutes, 60 marks, 16.7% of the qualification.
Check the OCR specification ↗The 4 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 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.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, mutualism and parasitismWhat interdependence is and why losing one species changes a whole community, predation, mutualism with the example of bees and flowers, parasitism with the example of a tapeworm, and what plants and animals compete for.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Define population, community and ecosystem in that order, from the smallest level of organisation to the largest.
Key term
Name two elements that are cycled between the living and non-living parts of an ecosystem.
Process
Which process removes carbon dioxide from the air in the carbon cycle?
Key term
What is meant by interdependence in a community?
Key term
What are the abiotic components of an ecosystem?
Process
Name two processes that return carbon dioxide to the air in the carbon cycle.
Key term
What is predation?
Key term
What are the biotic components of an ecosystem?
Key term
Describe how the carbon in a dead animal returns to the air.
Key term
List the levels of organisation in an ecosystem, from the smallest to the largest.
Key term
What is mutualism?
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.
Mutualism vs Parasitism
Mutualism: close relationship between two species in which both of them benefit. Parasitism: relationship in which one organism lives on or in a host and harms it.
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 Combined Science Biology?
- 4 subtopics: cycling materials, and the role of microorganisms, the carbon and water cycles, and decomposition, levels of organisation, and abiotic and biotic factors and interdependence, competition, mutualism and parasitism. Each one has its own page with questions and model answers.
- How is Community Level Systems organised?
- By the OCR J250 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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