Ecosystems | OCR A-Level Biology A (H420)
Ecosystems
- 52 questions
- 4 subtopics
- Module 6: Genetics, evolution and ecosystems
- Component 02 and Component 03
Ecosystems is the fifth section of Module 6.
It covers the biotic and abiotic factors that shape an ecosystem, why so little biomass passes between trophic levels, the nitrogen and carbon cycles, succession from pioneer species to climax community, and how distribution and abundance are estimated.
Sample questions from Ecosystems
Answer each one closed book first, then open the answer.
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Ecosystems, biotic and abiotic factors
Give an example of a large ecosystem.
Show the answer
A playing field. -
Ecosystems, biotic and abiotic factors
Name four examples of biotic factors.
Show the answer
Competition, predation, disease, and availability of food. -
Biomass transfer between trophic levels
State the formula for calculating the efficiency of biomass transfer.
Show the answer
Efficiency = (biomass transferred ÷ biomass intake) × 100. -
Biomass transfer between trophic levels
State one way humans can manipulate biomass transfer by altering food web structure.
Show the answer
Simplifying food webs (e.g. removing competitor species so more energy flows to the target organism). -
The nitrogen and carbon cycles
What is nitrogen fixation?
Show the answer
The conversion of atmospheric nitrogen gas (N₂) into ammonia. -
The nitrogen and carbon cycles
Between which reservoirs does carbon move in the carbon cycle?
Show the answer
The atmosphere, living organisms, and fossil fuels (as well as oceans and rocks). -
Succession, distribution and abundance
What is deflected succession?
Show the answer
Succession that is prevented from reaching the climax community by human activity or natural events, maintaining the ecosystem at an earlier seral stage. -
Succession, distribution and abundance
What is a transect?
Show the answer
A line along which samples are taken at regular intervals to study changes in distribution across an environmental gradient.
The 4 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Ecosystems, biotic and abiotic factors | What an ecosystem is at every scale and what makes one dynamic, with examples of the biotic and abiotic factors acting within it. | 9 |
| Biomass transfer between trophic levels | How biomass is measured, why roughly a tenth passes to the next level, the efficiency calculation, and how farming manipulates the transfer. | 13 |
| The nitrogen and carbon cycles | Decomposers, nitrogen fixation, nitrification, assimilation, ammonification and denitrification with the bacteria involved, and the movement of carbon between reservoirs. | 16 |
| Succession, distribution and abundance | Pioneer species, climax communities and deflected succession, and estimating abundance with quadrats, transects, percentage cover and mark-release-recapture. | 14 |
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 sections
OCR A-Level Biology A Active Recall Guide
Every section, not just this one. 1,833 questions with their answers.