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IGCSE Environmental Management — Unit Exam 1 — Challenge

Unit Assessment practice — 4.2 Climate change · 5.1 Ecosystems · 5.2 Forest ecosystems — Section B is source led
90 minutes
60
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90:00
0680
This paper covers only what the school unit tests: 4.2 Climate change, 5.1 Ecosystems and 5.2 Forest ecosystems. Section A (Questions 1–3, 30 marks) tests knowledge and application. Section B (Questions 4–6, 30 marks) is source led, the way 0680 Paper 2 works: every answer there should lean on the chart or the table in front of you.

Instructions

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SECTION A — knowledge and application (Questions 1–3, 30 marks)
Question 1 — The greenhouse effect
Total: 10 marks
(a)[2]
Define the term greenhouse gas.
Model Answer — 1(a)
a gas that absorbs radiation
and emits the energy as thermal (heat) energy
two verbs, in this order: absorbs, then emits
⚠ If you missed marks here: "a gas that traps heat" or "stops heat escaping" contains neither verb the scheme wants and usually scores zero. The gases do not seal radiation in; they absorb it and emit it again. Write absorbs and emits and both marks are safe.
(b)[5]
Describe the natural greenhouse effect.
Model Answer — 1(b)
solar radiation passes through the Earth’s atmosphere
some solar radiation is absorbed by the land and oceans, heating the Earth
some solar radiation is reflected back into space
some radiation is absorbed and re-emitted back to the Earth’s surface by greenhouse gases and clouds
this natural process warms the Earth enough to support life
five marks, five steps, in order — one sentence per step and stop
⚠ If you missed marks here: the mark most often dropped is the last one — "warms the Earth enough to support life" feels like a nice ending but it is a marking point. The other classic error is drifting into fossil fuels and warming: the question said natural, and the natural greenhouse effect is not the thing causing climate change. Clouds are in the syllabus list too; include them.
(c)[3]
Explain the difference between the natural greenhouse effect and the enhanced greenhouse effect.
Model Answer — 1(c)
the mechanism is the same in both — the enhanced effect is not a different process
human activity has increased the concentration of greenhouse gases, so more radiation is absorbed and re-emitted back to the surface
the natural effect warms the Earth enough to support life; the enhanced effect causes global warming, which can result in climate change
⚠ If you missed marks here: two zero-scoring classics live in this part. "The ozone layer causes global warming" — ozone depletion and the enhanced greenhouse effect are different processes, and mixing them scores zero. And blaming the natural greenhouse effect for warming inverts the whole point: the natural effect is why the Earth is habitable, and it is the extra gas that causes the warming.
Question 2 — Causes of climate change, and the two kinds of response
Total: 10 marks
(a)[4]
Greenhouse gas concentrations in the atmosphere have risen. State two causes of this rise: one that releases carbon dioxide and one that releases methane. For each cause, explain the mechanism by which the gas is released.
Model Answer — 2(a)
carbon dioxide: combustion of fossil fuels (or cement manufacture, or rising population and energy use)
mechanism: coal, oil and gas contain carbon stored underground for millions of years; burning combines it with oxygen and releases carbon dioxide (cement: heating limestone releases carbon dioxide from the calcium carbonate itself)
methane: agriculture — digestion by cattle, decomposition of manure, or rice fields — or changes in land use
mechanism: name which source you mean, e.g. cattle release methane during digestion; drained wetlands release methane the waterlogged ground had been holding
⚠ If you missed marks here: "farming" on its own is too vague to mark — the syllabus names cattle digestion, manure decomposition and rice fields, so say which one you mean. And check your two causes release the gases the question asked for: deforestation is a carbon dioxide cause but its listed mechanism is a loss of uptake, which makes it a risky pick when the question says "releases".
(b)[2]
Explain how deforestation increases the concentration of carbon dioxide in the atmosphere, even when the felled trees are not burned.
Model Answer — 2(b)
fewer trees means less removal of carbon dioxide by photosynthesis
so carbon dioxide that would have been taken up stays in the atmosphere — the mechanism is the loss of a sink, not an emission (decomposition of the felled timber then adds the stored carbon on top)
⚠ If you missed marks here: the commonest wrong answer is "cutting down trees releases carbon dioxide". The question deliberately removed burning, so the answer has to be the loss of uptake: trees are a sink, and removing them removes the sink. Write the word photosynthesis and the first mark is safe.
(c)[4]
Strategies that reduce carbon footprints and climate change adaptation are two different kinds of response. Explain the difference, and give one named example of each.
Model Answer — 2(c)
reduction strategies attack the cause: they cut the amount of greenhouse gas released or remove it from the air
adaptation is altering behaviour, practices and infrastructure to adapt to the impacts of climate change that are already arriving
reduction example with how it works, e.g. reforestation and afforestation increase removal of carbon dioxide by photosynthesis; or taxation makes the high-carbon option the expensive one
adaptation example, e.g. improved flood defences, crops that resist warmer or drier conditions, legislation about building on floodplains, or building design and materials
⚠ If you missed marks here: a sea wall does not lower anyone’s carbon footprint by a gram — offering it as a reduction strategy scores zero, and offering solar panels as adaptation is the same mistake in reverse. Ask of your example: does it reduce the gas, or does it reduce the harm? That one question sorts every example onto the right side.
Question 3 — Ecosystems, energy and forests
Total: 10 marks
(a)[2]
A bat and an owl live in the same woodland. The bat catches flying insects at dusk; the owl hunts mice at night. Use this example to explain the difference between a habitat and a niche.
Model Answer — 3(a)
the habitat is the place where an organism lives — both animals share the same habitat, the woodland
the niche is the role the organism plays — what it eats, when it is active, what conditions it needs — so the two have different niches even in one habitat
⚠ If you missed marks here: habitat is the address; niche is the job. If a question asks for a niche and you answer with a place, you get nothing — say what the organism does. This example is chosen because it forces the distinction: same address, two different jobs.
(b)[2]
The producers in a grassland fix 50 000 kJ/m²/year. Assuming 10% of energy is transferred at each step, calculate the energy available to a secondary consumer. Show your working.
Model Answer — 3(b)
50 000 × 0.1 = 5 000 then 5 000 × 0.1 = 500   M1 for two transfers of 10%
= 500 kJ/m²/year   A1
producer to primary consumer is one transfer; primary to secondary is the second
⚠ If you missed marks here: count the transfers, not the levels — the miscount is always by one. A secondary consumer sits two arrows from the producer, so apply 10% twice: 500, not 5 000 and not 50. Show both lines of working; the method mark survives an arithmetic slip.
(c)[2]
Explain why a pyramid of energy is never inverted, even though a pyramid of numbers can be.
Model Answer — 3(c)
about 90% of the energy is lost at every transfer — in movement, respiration, digestion and excretion
so a trophic level can never contain more energy than the level below it, and each bar must be narrower than the one beneath
⚠ If you missed marks here: the contrast is the point. Numbers ignore size — one oak can feed ten thousand aphids, so a numbers pyramid can bulge. Energy cannot do that, because energy is lost at every single step. If your answer never mentions energy being lost, it has not explained anything.
(d)[2]
Write out the definition of sustainable management of forests.
Model Answer — 3(d)
balancing the needs of the environment, wildlife and humans
while conserving forests for future generations
⚠ If you missed marks here: "using forests without destroying them" earns one mark instead of two, because it names no groups and no timescale. The definition has three groups to balance — environment, wildlife, humans — and one time phrase, future generations. All four words matter.
(e)[2]
A forest is described as both a carbon sink and a carbon store. Explain the difference between the two terms.
Model Answer — 3(e)
a sink absorbs carbon dioxide: growing trees remove it from the air by photosynthesis
a store holds carbon already fixed — locked in the wood and the soil
⚠ If you missed marks here: the trap answer is the same two ideas with the labels swapped — "a sink holds carbon; a store absorbs it". Anchor it to the verbs: the sink is the taking in, the store is the holding. A growing forest does both at once, which is exactly why questions ask you to separate them.
SECTION B — source led (Questions 4–6, 30 marks). Quote figures from the sources.
Question 4 — Source A, carbon dioxide in the atmosphere
Total: 10 marks
SOURCE A — Mean atmospheric carbon dioxide concentration, measured at one observatory, 1960–2020
300 320 340 360 380 400 420 1960 1970 1980 1990 2000 2010 2020 317 326 339 354 369 390 414 carbon dioxide concentration / ppm year
Each point is the mean concentration for that year, in parts per million (ppm). The observatory is on a mountain far from cities, so the readings are not dominated by any one local source.
(a)(i)[1]
Using Source A, state the carbon dioxide concentration in 1960.
Model Answer — 4(a)(i)
317 ppm
the figure and its unit are both needed
⚠ If you missed marks here: a read-off mark wants the number and the unit. 317 on its own is half an answer, and "about 320" throws away a value the chart prints for you. When a source labels its points, use the printed figure exactly.
(a)(ii)[3]
Calculate the increase in concentration between 1960 and 2020, and then express that increase as a percentage of the 1960 value. Give the percentage to 3 significant figures. Show your working.
Model Answer — 4(a)(ii)
414 − 317   M1 for the correct subtraction
= 97 ppm   A1
97 ÷ 317 × 100 = 30.6%   A1 — the divisor is the 1960 value, 317
⚠ If you missed marks here: the percentage error to avoid is dividing by the wrong base. "As a percentage of the 1960 value" means divide by 317, not by 414 — dividing by 414 gives 23.4%, which looks plausible and is wrong. And 30.6274… rounded to 3 significant figures is 30.6, not 30.63.
(b)[3]
Describe the trend shown in Source A. Use figures from the chart in your answer.
Model Answer — 4(b)
the concentration rises across the whole period, from 317 ppm in 1960 to 414 ppm in 2020 — no decade shows a fall
the rise is accelerating: the increase was 9 ppm in the 1960s (317 to 326) but 24 ppm in the 2010s (390 to 414)
a third supported point, e.g. almost half the whole 97 ppm increase (45 ppm) happened in the last two decades
1 mark per point, maximum 3; a point with no figure attached caps the answer at 1
⚠ If you missed marks here: "it goes up" is one mark, however elegantly written, because it could have been said without looking. A describe on a line graph wants direction and rate: is the line rising, and is it rising faster or slower over time? Compare the size of two decade steps and the second mark arrives on its own.
(c)[2]
Explain how the trend in Source A leads to a rise in global surface temperature.
Model Answer — 4(c)
carbon dioxide is a greenhouse gas, so a higher concentration means more radiation is absorbed and re-emitted back to the surface — the enhanced greenhouse effect
so the surface warms further — global warming, which can result in climate change
⚠ If you missed marks here: the explain mark is for the mechanism, and the mechanism is absorb-and-re-emit — not "the gas traps heat", and not the ozone layer, which is a different process entirely. Link the chart to the physics in one chain: more gas, more radiation returned to the surface, warmer surface.
(d)[1]
State one thing that Source A does not tell you.
Model Answer — 4(d)
it does not show which activities released the carbon dioxide
it does not show temperature, or any impact — only the concentration
it does not show the other greenhouse gases, such as methane and water vapour
it is one observatory, so it does not prove the pattern is the same everywhere
any one of these scores
⚠ If you missed marks here: this AO3 mark is free once you have the habit. One variable hides all the others: a concentration chart shows no causes, no temperatures, no other gases. Do not answer with something the chart does show, and do not answer "it does not show the future" alone without saying why that matters less than the missing causes.
Question 5 — Source B, forest area in five countries
Total: 10 marks
SOURCE B — Forest area in five countries, 2000 and 2020
CountryForest area 2000 / thousand km²Forest area 2020 / thousand km²
P49204310
Q13501180
R620655
S22101620
T890850
The figures are total forest area, from satellite surveys, rounded to the nearest 10 thousand km². Country S is mostly tropical forest on land also suitable for commercial farming.
(a)(i)[1]
Using Source B, identify the country whose forest area increased, and state the size of the increase.
Model Answer — 5(a)(i)
country R, an increase of 35 thousand km² (620 to 655)
the letter and the figure are both needed
⚠ If you missed marks here: an identify from a table wants the label and the figure. Scan the whole column before answering — four of the five countries lost forest, and the one gain is easy to miss if you stop reading at the first row that changed.
(a)(ii)[3]
Calculate the percentage loss of forest area in country S between 2000 and 2020. Give your answer to 3 significant figures. Show your working.
Model Answer — 5(a)(ii)
2210 − 1620 = 590   M1 for the loss
590 ÷ 2210 × 100   M1 — the divisor is the 2000 value
= 26.7%   A1 (26.696… to 3 significant figures)
⚠ If you missed marks here: a percentage change is always measured against the starting value: divide by 2210, not by 1620. Dividing by 1620 gives 36.4%, which is a different quantity (the loss as a share of what remains). Write both method lines down — each carries its own mark even if the final rounding slips.
(b)[3]
Describe the pattern shown in Source B. Use figures from the table in your answer.
Model Answer — 5(b)
four of the five countries lost forest over the twenty years; only R gained (620 to 655)
the losses vary widely: P lost the largest area, 610 thousand km², while S lost the largest share, 26.7% (590 of 2210)
a third supported point, e.g. T’s loss is small in both senses — 40 thousand km², about 4.5% — so the losses are concentrated in P, Q and S
1 mark per point, maximum 3; a point with no figure attached caps the answer at 1
⚠ If you missed marks here: the sharpest describe point on a table like this is the one that separates the largest area lost from the largest percentage lost — they are different countries here (P and S), and noticing that is exactly the kind of comparison AO3 pays for. "Most countries lost forest" with no numbers is a single mark.
(c)[3]
Explain how the loss of forest in country S could reduce rainfall in the region downwind of it.
Model Answer — 5(c)
forests return large amounts of water to the air by transpiration; with fewer trees there is less transpiration
so there is less water vapour in the air, and less cloud forms
so less rain falls downwind, and the region becomes drier
⚠ If you missed marks here: "run-off carries the water away faster" is true but it is the wrong route — it explains where surface water goes, not how much vapour enters the air. The chain the syllabus wants runs through transpiration: less transpiration, less vapour, less cloud, less rain. Three links, three marks.
Question 6 — Using Source A and Source B together
Total: 10 marks
(a)[4]
Explain how the changes shown in Source B could contribute to the trend shown in Source A.
Model Answer — 6(a)
the lost forest removed carbon dioxide by photosynthesis, so less carbon dioxide is now being taken out of the air
and burning or decomposition of the felled timber releases the carbon the trees had stored
both effects raise the atmospheric concentration, which is consistent with the rise in Source A — e.g. the accelerating climb to 414 ppm
and the link runs both ways: the resulting warming dries forests, so trees die and fires burn larger areas — climate change is itself a cause of deforestation, a feedback loop
⚠ If you missed marks here: full marks needs both carbon routes — the lost uptake and the released store — because one removes less and the other actively adds. Also be careful with the word "proves": Source B is five countries and Source A is one observatory, so the sources are consistent with the link, not proof of it. Saying so is worth credit, not a penalty.
(b)[6]
The government of country S proposes to rely on reforestation alone to reduce its contribution to climate change. Using both sources and your own knowledge, discuss the benefits and limitations of this proposal. Reach a judgement.
Model Answer — 6(b)
benefits: replanting increases removal of carbon dioxide by photosynthesis, directly reversing the loss of uptake; and it restores habitat, reduces soil erosion and can provide timber and income at the same time
limitation — timescale: trees take decades to absorb much carbon, so the strategy does little about emissions this decade
limitation — land and quality: land planted with trees cannot be farmed, and a single-species plantation stores carbon but supports far less biodiversity than the forest S lost; the carbon is released again if the trees burn or are felled
limitation — scope: reforestation does nothing about the largest source of carbon dioxide, the combustion of fossil fuels, so on its own it cannot stop the rise in Source A
using the sources: S lost 590 thousand km² (26.7%) in twenty years, so replanting has a large area to work with — but Source A climbed 24 ppm in the 2010s while the world already had far more forest than S can plant, which puts the scale of the proposal in proportion
judgement: a reasoned conclusion that follows from the points made, e.g. reforestation is worth doing for its carbon and its other benefits, but as the only strategy it is too slow and too small; it needs to sit alongside strategies that cut what is released
⚠ If you missed marks here: a discuss answer that lists only advantages is capped, however many it lists — and so is one that never reaches a judgement. Run the four-part move: benefit, limitation, who bears the cost, over what timescale. The single word alone in the question is the examiner telling you where the best limitation lives: what does this strategy NOT touch?

Self-Assessment

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IGCSE Environmental Management 0680 — Unit Exam 1 — 4.2 Climate change, 5.1 Ecosystems, 5.2 Forest ecosystems — Challenge
For examination preparation only. Not an official Cambridge Assessment paper.