Ecosystems and Material Cycles | Edexcel GCSE Biology, Foundation tier (1BI0)

Ecosystems and Material Cycles

152 questions
12 subtopics
Paper 2
Paper 2

Ecosystems and Material Cycles is examined in Paper 2, Biology 2.

It covers levels of organisation and interdependence, abiotic and biotic factors, parasitism and mutualism, sampling with quadrats and transects and estimating population size, energy transfer between trophic levels, human impact on biodiversity, food security, the carbon, water and nitrogen cycles, and the factors affecting decomposition and calculating the rate of decay.

Sample questions from Ecosystems and Material Cycles

Answer each one closed book first, then open the answer.

Levels of organisation and interdependence

Place the terms community, individual organism, ecosystem and population in order from the smallest level of organisation to the largest.

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Individual organism, then population, then community, then ecosystem.
Abiotic and biotic factors in a community

State three things that animals in a habitat compete for.

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Food, water and territory or mates.
Sampling with quadrats and transects

What is a belt transect?

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A belt transect is a line laid across a habitat along which quadrats are placed to record how the species present change with distance.
Estimating population size from field data

Explain why a population size worked out from quadrat data is only an estimate.

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Only a small fraction of the area is actually counted, and that sample may not exactly match the whole site.
Human impact on ecosystems and biodiversity

What is eutrophication?

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Eutrophication is the enrichment of water with nutrients such as nitrates, which causes excessive growth of algae.
Food security

Give two environmental changes caused by human activity that can lower crop yields.

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Changed rainfall patterns bringing drought or flooding, and the loss of fertile topsoil through erosion.
The water and nitrogen cycles

Describe how distillation turns sea water into potable water.

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The sea water is heated so that pure water evaporates, and the vapour is then cooled and condensed, leaving the salts behind.
Factors affecting the rate of decomposition

Explain why a compost heap should be kept damp but never waterlogged.

Show the answer
The microorganisms need water to grow, but waterlogging drives the air out and slows aerobic decay.

The 12 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
Levels of organisation and interdependence	Individuals, populations, communities, habitats and ecosystems and their order, interdependence through food, shelter, pollination and seed dispersal, how losing one species affects others in a food web, and why an interdependent community stays balanced.	13
Abiotic and biotic factors in a community	Abiotic and biotic factors, how temperature, light, drought and pollution shape a community, what plants and animals compete for, and the cycle of predator and prey numbers.	10
Parasitism and mutualism	Parasitism and mutualism, with tapeworms, fleas and mistletoe as parasites, and oxpeckers and buffalo, cleaner fish, nitrogen-fixing bacteria in pea plants, and chemosynthetic bacteria in deep-sea tube worms as mutualistic partners.	9
Sampling with quadrats and transects	Using random quadrats to find the mean number of a plant per square metre, generating random coordinates, percentage cover, belt transects across a changing habitat, measuring light and soil moisture, sample size and sources of error, and the mean, median and mode of quadrat counts.	15
Estimating population size from field data	Scaling a quadrat mean up to a whole site, working the mean per square metre from quadrats of different sizes, why the result is only an estimate, and transect counts.	8
Energy transfer between trophic levels	Trophic levels, the energy lost as heat, faeces and urine, why food chains stay short, pyramids of biomass, and calculating the percentage efficiency of a transfer.	16
Human impact on ecosystems and biodiversity	Biodiversity, the harm and benefits of fish farming, non-indigenous species and their effects on native wildlife, eutrophication from fertiliser and sewage, why biodiversity keeps ecosystems stable, conserving endangered species through captive breeding and protected habitats, reforestation, and the economic value of biodiversity.	18
Food security	Food security and how a rising population, increasing meat consumption, overfishing, new pests and pathogens, environmental change, biofuel crops and the rising cost of fertiliser and fuel all threaten it.	8
The carbon cycle	Why materials must be recycled, the biotic and abiotic parts of material cycles, decomposers, and the carbon cycle, with photosynthesis removing carbon dioxide, respiration and combustion returning it, carbon passing along food chains, and the effects of burning fossil fuels and clearing forests.	14
The water and nitrogen cycles	Evaporation, transpiration, condensation and precipitation in the water cycle, potable water and desalination by distillation, why sea water dehydrates, and the nitrogen cycle, with nitrogen-fixing, nitrifying and denitrifying bacteria, decomposers, legume crop rotation, fertilisers and draining waterlogged soil.	17
Factors affecting the rate of decomposition	The warmth, water and oxygen that decay microorganisms need, how refrigeration, freezing, drying, salting, vacuum packing and canning preserve food, and how turning, heat, moisture, shredding and temperature affect the rate of decay in a compost heap.	16
Calculating the rate of decay	Mean rate of decay from mass lost over time, comparing rates at two temperatures, mass remaining after a period or after a percentage loss, and why decay slows later.	8

Ecosystems and Material Cycles is 152 of the 1,218 questions in the guide.Get the guide, £7

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.

Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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.
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.