AQA GCSE Biology (8461), Higher tier · Ecology › Organisation of an ecosystem
Practise How materials are cycled. 14 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
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Name the type of organism that returns carbon from dead plants and animals to the atmosphere.
Microorganisms (decomposers)
Name the process by which plants lose water vapour from their leaves.
Transpiration
Microorganisms also return substances to the soil that plants need for healthy growth. Name this type of substance.
Mineral ions
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy5 marks
Carbon is cycled between living organisms and the atmosphere.
(a) Which process removes carbon dioxide from the atmosphere? Tick (✓) one box.[1]
Combustion
Decay
Photosynthesis
Respiration
(b) Which two processes return carbon dioxide to the atmosphere? Tick (✓) two boxes.[2]
Combustion of fossil fuels
Feeding
Photosynthesis
Respiration
Transpiration
(c) Name the type of organism that returns carbon from dead plants and animals to the atmosphere.[1]
(d) Why is it important that materials such as carbon are recycled in the living world?[1]
Show the answer and mark scheme
(a)Answer: Photosynthesis
(b)Answer: Combustion of fossil fuels; Respiration
(c)Answer: Microorganisms (decomposers)
microorganisms / decomposers (bacteria or fungi)
(d)
to provide the building blocks for future organisms / so that materials are available for new organisms
Question 2Medium8 marks
The water cycle provides fresh water for plants and animals on land.
(a) Name the process by which plants lose water vapour from their leaves.[1]
(b) Describe how water from the sea can become rain that falls on land.[3]
(c) Explain why the water cycle is important to living organisms on land.[2]
(d) Give two ways in which animals return water to the environment.[2]
Show the answer and mark scheme
(a)Answer: Transpiration
transpiration
(b)
water evaporates from the sea (heated by the Sun)
the water vapour rises, cools and condenses to form clouds
the clouds are blown over the land by the wind
the water falls as precipitation / rain
(c)
it provides fresh water on land
water is needed by plants for photosynthesis / to keep cells turgid / for transport
animals need water for drinking / for chemical reactions in cells
water drains back to the seas and is continuously evaporated and precipitated, so the supply is renewed
(d)
breathing out water vapour
sweating
urine
faeces
Question 3Hard8 marks
A student investigated the role of microorganisms in cycling materials. The student set up two containers of soil, each with 20.0 g of dead leaves on the surface.
Container A: the soil and leaves were heated in an oven to kill all microorganisms.
Container B: the soil and leaves were not heated.
Both containers were covered with cotton wool, kept moist and kept at 25 °C. After 8 weeks the mass of leaves left in container A was 19.6 g and in container B was 7.2 g.
(a) Calculate the percentage decrease in the mass of leaves in container B.[2]
(b) Explain the difference between the results for containers A and B.[3]
(c) Seedlings grown in soil from container B grew better than seedlings grown in soil from container A. Explain why.[2]
(d) Suggest one other way in which heating the soil could have affected the growth of the seedlings.[1]
Show the answer and mark scheme
(a)Answer: 64%
(20.0 − 7.2) ÷ 20.0 × 100
64 (%)
(b)
container B contained microorganisms / decomposers but in A they had been killed
microorganisms secrete enzymes that break down / digest the dead leaves
the microorganisms use the products for respiration, releasing carbon dioxide (so the mass decreases)
in A there was no decay, so the mass hardly changed (the small loss may be water evaporating)
(c)
decay in container B released mineral ions (e.g. nitrate ions) into the soil
plants need mineral ions for growth, e.g. nitrate to make proteins / amino acids
(d)
killed other organisms such as earthworms that improve the soil
dried out the soil / changed the soil structure
changed the chemicals / mineral content of the soil