Community Level Systems | OCR GCSE Combined Science Biology, Higher tier (J250)
Community Level Systems
- 51 questions
- 4 subtopics
- Paper 8 (Biology)
- Paper 8 (Biology)
Community Level Systems is examined in Paper 8 (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.
Sample questions from Community Level Systems
Answer each one closed book first, then open the answer.
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Cycling materials, and the role of microorganisms
Explain why materials such as carbon and nitrogen must be recycled in an ecosystem.
Show the answer
The supply of them is limited, so they have to be returned to the non-living surroundings for other organisms to take up and use again. -
Cycling materials, and the role of microorganisms
How do decomposers return carbon to the air?
Show the answer
They respire as they break down dead material, releasing carbon dioxide. -
The carbon and water cycles, and decomposition
Describe how the carbon in a dead animal returns to the air.
Show the answer
Decomposers feed on the remains and release carbon dioxide as they respire. -
The carbon and water cycles, and decomposition
Explain why the water cycle provides land organisms with fresh water.
Show the 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. -
Levels of organisation, and abiotic and biotic factors
All the oak trees growing in one wood are an example of which level of organisation?
Show the answer
A population. -
Levels of organisation, and abiotic and biotic factors
Explain how light intensity affects the plants growing on a woodland floor.
Show the answer
Plants in deep shade photosynthesise less, so they grow more slowly and fewer of them survive than in a bright gap. -
Interdependence, competition, mutualism and parasitism
What is predation?
Show the answer
One organism, the predator, hunts and eats another organism, the prey. -
Interdependence, competition, mutualism and parasitism
What is parasitism?
Show the answer
A relationship in which a parasite lives on or in a host, gaining from it while harming the host.
The 4 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Cycling materials, and the role of microorganisms | 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. | 19 |
| The carbon and water cycles, and decomposition | 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. | 8 |
| Levels of organisation, and abiotic and biotic factors | The 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. | 16 |
| Interdependence, competition, mutualism and parasitism | What 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. | 8 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
OCR GCSE Combined Science Biology, Higher tier Active Recall Guide
Every topic, not just this one. 861 questions with their answers.