Ecosystems | Edexcel A-Level Biology B (9BI0)
Ecosystems
- 217 questions
- 12 subtopics
- Topics 8 to 10, examined on Paper 2 and Paper 3
- Paper 2 and Paper 3
How ecosystems are described and sampled, the statistics used to test ecological data, how energy passes between trophic levels and how nutrients are recycled, how communities change over time, and the human effects that make management necessary..
It covers ecosystems, habitats and niches, pyramids of numbers, biomass and energy, ecological techniques for measuring distribution, choosing the right ecological technique, presenting data in tables and graphs, statistical tests in ecology, productivity and energy transfer efficiency, decomposers and nutrient cycling, succession, biotic and abiotic factors in population change, human influences on ecosystems and sustainability, resource management and peer review.
Sample questions from Ecosystems
Answer each one closed book first, then open the answer.
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Ecosystems, habitats and niches
Give an example of a very large ecosystem.
Show the answer
An ocean or a tropical rainforest. -
Pyramids of numbers, biomass and energy
Why are pyramids of energy always upright?
Show the answer
Energy is lost at each transfer, so each successive trophic level always has less energy than the one below, providing the most accurate representation of energy flow. -
Choosing the right ecological technique
Why might different sampling methods give different estimates of population size?
Show the answer
Spatial distribution patterns of organisms can cause variation in estimates depending on the sampling method used. -
Presenting data in tables and graphs
When should data be plotted as a line graph?
Show the answer
When both variables are continuous and the independent variable has been deliberately changed, such as rate of transpiration against wind speed, with the independent variable on the x-axis. -
Productivity and energy transfer efficiency
Explain how respiration causes energy loss between trophic levels.
Show the answer
Organisms release energy as heat during metabolic processes; this heat energy cannot be transferred to the next trophic level. -
Decomposers and nutrient cycling
What nitrogen-containing compound is released during ammonification?
Show the answer
Ammonia (NH₃). -
Biotic and abiotic factors in population change
How does water availability affect population size?
Show the answer
Water availability limits survival and reproduction; populations decline when water is scarce and increase when water is abundant. -
Human influences on ecosystems
Explain how increased atmospheric carbon dioxide affects marine organisms through ocean acidification.
Show the answer
More carbon dioxide dissolves in seawater, forming carbonic acid that lowers the pH and reduces carbonate ions, so corals, molluscs and some plankton struggle to build calcium carbonate shells and skeletons, with effects along food chains.
The 12 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Ecosystems, habitats and niches | Recall questions on the biotic and abiotic components of an ecosystem, examples of small and large ecosystems, how the components interact, and trophic levels from producers to tertiary consumers. | 11 |
| Pyramids of numbers, biomass and energy | Recall questions on pyramids of numbers, biomass and energy, what each shows, their advantages and disadvantages, and why pyramids of numbers and biomass can be inverted while pyramids of energy cannot. | 13 |
| Ecological techniques for measuring distribution | Recall questions on random placement of point, frame and gridded quadrats, line and belt transects, the ACFOR scale and its limits, and when percentage cover or individual counts suit a species. | 16 |
| Choosing the right ecological technique | Recall questions on transects and interrupted belt transects, random and systematic sampling, choosing quadrat size, comparing the reliability of methods, estimating population size, and the safe and ethical use of organisms and risk assessment in fieldwork. | 15 |
| Presenting data in tables and graphs | Recall questions on laying out a results table with consistent decimal places, frequency tables and modal classes, and when to choose a bar chart, histogram, line graph or scattergram, with how to draw and label the axes. | 9 |
| Statistical tests in ecology | Recall questions on when and how to use the t-test and Spearman's rank correlation coefficient, degrees of freedom and critical values, and calculating the mean, median, mode, range and standard deviation of ecological data. | 39 |
| Productivity and energy transfer efficiency | Recall questions on gross and net primary productivity, calculating the efficiency of transfer, and why energy is lost at each level. | 39 |
| Decomposers and nutrient cycling | Recall questions on the role of microorganisms in decay, and on the recycling of nitrogen and carbon within an ecosystem. | 9 |
| Succession | Recall questions on colonisation, primary and secondary succession, pioneer species and how they change abiotic conditions, and the climax community, climatic climax and plagioclimax. | 13 |
| Biotic and abiotic factors in population change | Recall questions on biotic factors such as predation, competition, disease and food supply, abiotic factors such as temperature, light, water, pH and mineral ions, and investigating how an abiotic factor affects distribution or morphology along a transect. | 20 |
| Human influences on ecosystems | Recall questions on overfishing and its effects on breeding populations and food webs, CITES, balancing use against conservation, the effects of climate change on species ranges, timing, coral, ocean pH and pests, and interpreting carbon dioxide, ice core and flowering data. | 22 |
| Sustainability, resource management and peer review | Recall questions on sustainable resource use, catch quotas, closed seasons, mesh sizes and marine protected areas, approaches to reducing climate change, and how peer review, journals and conferences validate evidence. | 11 |
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
Edexcel A-Level Biology B Active Recall Guide
Every topic, not just this one. 2,073 questions with their answers.