Ecosystems & Material CyclesEdexcel GCSE Biology: Topic test

20 questions, 54 marks

Edexcel GCSE Biology

Ecosystems & Material Cycles topic test

Total 54 marks

Name

Class

Date

1
Ecologists compared a population of gorse bushes on two slopes of a heathland hill. The south-facing slope receives strong sunlight for most of the day and has dry, free-draining soil. The north-facing slope is shaded for most of the day and has damp, waterlogged soil. The ecologists placed ten 1 m by 1 m quadrats at random positions along each slope and counted the number of gorse plants rooted inside each quadrat.
(a)
Which abiotic factor most directly limits the rate of photosynthesis, and therefore gorse growth, on the shaded north-facing slope?
[1 mark]
ALight intensity
BWind speed
CPredation
DSoil pH
(b)
Which of these best explains why the ecologists placed the quadrats at random positions rather than choosing the positions themselves?
[1 mark]
AIt guarantees every gorse plant on the slope is counted
BIt removes bias, so the sample is more likely to be representative
CIt increases the total number of quadrats used
DIt removes the need to repeat the survey
(c)
State one biotic factor, other than the gorse plants themselves, that could also affect the number of gorse plants found on each slope, and explain how it could have this effect.
[2 marks]
Total for question 1: 4 marks
2
A rocky-shore food chain is studied: kelp → limpets → oystercatchers. Ecologists measure the total biomass present at each trophic level over one year and record: kelp 12,000 kg, limpets 1,200 kg, oystercatchers 90 kg.
(a)
Which of these processes does NOT account for energy being lost between the kelp and the limpets in this food chain?
[1 mark]
AMovement
BHeat loss through respiration
CPhotosynthesis by the kelp
DEgestion of undigested material
(b)
Why do food chains such as this one rarely have more than about five trophic levels?
[1 mark]
APredators are territorial
BEach level has fewer organisms available to reproduce
CAn ecosystem cannot support many different species
DNot enough energy remains to support a further trophic level
(c)
Calculate the percentage efficiency of energy transfer from the kelp to the limpets, using the biomass figures as an estimate of energy transferred. Show your working.
[2 marks]
Total for question 2: 4 marks
3
A gardener sets up two identical bins containing the same mass of shredded vegetable peelings and grass cuttings. Bin 1 is kept in a sunny spot and is turned with a fork every week to mix in air. Bin 2 is kept in a shaded, sealed corner of the garden and is left completely undisturbed. After eight weeks, the contents of Bin 1 have broken down into fine, dark compost, while Bin 2 still contains mostly recognisable, undecomposed plant material.
(a)
Explain why the plant material in Bin 1 broke down faster than the plant material in Bin 2.
[3 marks]
(b)
Explain how bacteria in the compost convert the nitrogen-containing compounds in the decaying plant material into a form that plants growing nearby could absorb, and name one process that could return some of this nitrogen to the atmosphere.
[4 marks]
Total for question 3: 7 marks
4
A local council is deciding between two proposals for 200 hectares of degraded pasture. Proposal A converts the land into intensive dairy cattle farming, with the pasture reseeded as a single grass species and treated regularly with artificial fertiliser to maximise grass growth for the cattle. Proposal B converts two-thirds of the land into arable fields growing wheat, with the remaining third planted as a native broadleaf woodland reserve.
(a)
Analyse how each proposal would affect local biodiversity, and evaluate which proposal is more likely to support biodiversity in the area over the long term.
[6 marks]
(b)
Evaluate the impact of each proposal on national food security, using the biological factors affecting food security that you have studied.
[6 marks]
Total for question 4: 12 marks
5
A shipping company begins releasing ballast water from ocean-going tankers into a previously isolated volcanic island lagoon. Within two years, a fast-growing seaweed species that arrived in the ballast water has begun to smother the native coral in the lagoon, and the population of a native reef fish that depends on the coral for shelter has fallen sharply.
(a)
Which term describes the fast-growing seaweed that has been introduced into the lagoon, where it did not previously live?
[1 mark]
AEndemic species
BNon-indigenous (non-native) species
CKeystone species
DDecomposer
(b)
Which of these is the most likely direct cause of the decline in the native reef fish population?
[1 mark]
ALoss of the coral habitat the fish depends on for shelter
BIncreased predation by organisms carried in the ballast water
CA decrease in the salinity of the lagoon
DAn increase in the water temperature of the lagoon
(c)
Suggest two negative effects on the wider biodiversity of the lagoon if the invasive seaweed continues to spread and smother more of the coral.
[2 marks]
Total for question 5: 4 marks
6
A country that currently imports 60% of its wheat announces that rising global temperatures and more frequent droughts in its main wheat-exporting trade partners have caused wheat prices to double over the past three years. Over the same period, the country's own population has grown by 15%, and a national dietary survey shows a clear shift towards eating more meat.
(a)
Which factor described here is most directly responsible for the doubling of wheat prices?
[1 mark]
APopulation growth in the importing country
BA dietary shift towards eating more meat
CIncreased land use for biofuel production
DReduced crop yields caused by drought in exporting countries
(b)
Which of these factors puts additional pressure on food security by requiring more land, water and crops to produce the same amount of food energy for people?
[1 mark]
AFalling wheat prices
BPopulation decline
CA dietary shift towards eating more meat
DImproved crop irrigation technology
(c)
Explain why a shift towards higher meat consumption places greater pressure on food security than an equivalent shift towards eating more crops directly.
[2 marks]
Total for question 6: 4 marks
7
A city council measures air quality along a road leading out of the city centre into the surrounding countryside, by recording the lichen species growing on tree trunks at ten sites spaced along the 10 km route. Near the city centre, only crusty lichen species that can tolerate high levels of sulfur dioxide are found. Further from the city centre, bushy lichen species, which are known to be far more sensitive to sulfur dioxide, become increasingly common.
(a)
Explain how the council can use the pattern of lichen species found at the different sites as an indicator of air pollution levels.
[3 marks]
(b)
Explain how the burning of fossil fuels by vehicles travelling along the road contributes to the release of carbon dioxide as part of the carbon cycle, and describe two ways in which carbon can be removed from the atmosphere to balance this release.
[4 marks]
Total for question 7: 7 marks
8
Marine biologists studying a kelp forest off a rocky coastline record that the local sea otter population has fallen from around 300 to 60 individuals over 15 years, following a large increase in commercial otter hunting in a neighbouring, unprotected area. Over the same 15 years, populations of sea urchins, which graze on kelp and are the otters' main prey, have increased fivefold, and the area of kelp forest in the study region has decreased by 70%.
(a)
Analyse how the decline in the sea otter population has led to the decrease in the area of kelp forest, in terms of feeding relationships and interdependence within the ecosystem.
[6 marks]
(b)
Evaluate how the loss of kelp forest is likely to affect the wider community of organisms in the area, and suggest two abiotic factors that could also be affected by the reduced kelp cover.
[6 marks]
Total for question 8: 12 marks

End of questions