Cambridge OCR GCSE (9-1) · Gateway Science - Biology A - J247
5 multiple-choice questions marked as you go, and 5 written questions with worked solutions. All on Ecosystems.
A food chain in a woodland consists of:
Oak tree → Caterpillars → Blue tits → Sparrowhawk
The total biomass at the oak tree level is \(15000\text{ kg}\). The efficiency of biomass transfer from the oak tree to the caterpillars is \(12\%\). Calculate the biomass of the caterpillars in kilograms.
Nitrogen-fixing bacteria live in the root nodules of leguminous plants like clover. This relationship is an example of:
A student investigates the rate of decay of biological material. At the start of the experiment, the mass of the organic waste is \(5.0\text{ kg}\). After \(20\) days, the mass has decreased to \(3.2\text{ kg}\).
Calculate the average rate of decay in \(\text{g/day}\).
Microorganisms such as fungi and bacteria play a vital role in ecosystems as decomposers. How do these organisms contribute to the continuous cycling of chemicals?
Which abiotic factor is most likely to cause a decrease in the rate of decomposition in a waterlogged soil environment?
A woodland community consists of bluebells, oak trees, and various insects. Explain the difference between this community and the woodland ecosystem.
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A student investigates the rate of decay of compost at different temperatures. Explain, in terms of microbial activity, why the rate of decay increases as temperature rises from \(10^{\circ}C\) to \(40^{\circ}C\).
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Explain why the efficiency of biomass transfer between a producer and a primary consumer is typically only around \(10\%\).
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A student investigates the rate of decomposition of organic material. They place 500g of fresh compost in a bin and measure the mass remaining over several weeks.
At the start, the mass is 500g. After 4 weeks, the mass is 420g. After 8 weeks, the mass is 360g.
(a) Calculate the percentage of mass lost between week 0 and week 8.
(b) Calculate the average rate of decay in grams per week (\(g/week\)) over the 8-week period.
(c) Explain how temperature and oxygen availability affect the rate of decomposition by microorganisms.
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Biotic and abiotic factors affect the distribution of organisms.
(a) List two abiotic factors and two biotic factors that could affect a population of plants in a woodland.
(b) A scientist observes that bluebells grow earlier in the spring than many trees grow their leaves. Explain this observation in terms of competition for light.
(c) Explain how the introduction of a new predator might affect the entire community, not just its direct prey.
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