Chapter 4 Practice Paper: Ecosystems — mark scheme (print)

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QQ/S2SCI/CH4

Secondary 2 · Lower Secondary Science (G2 / G3)

Mark scheme

Ecosystems

Chapter 4 Practice Paper · Maximum mark: 30

Notes for markers

Award one mark for each point marked [1], up to the marks shown for the part.
Accept answers worded differently that show the same understanding.
Units are required where the answer line shows one. ecf: allow an error carried forward.

Section A: Multiple-choice questions[10 marks]

Question	Answer
1	AAbiotic factors are non-living. Temperature, light, air, water, minerals and acidity are examples.	1
2	CThe arrow points from the rabbit to the fox, so energy is transferred to the fox.	1
3	BThe cleaner fish get food and the larger fish is left healthier, so both benefit. That is mutualism.	1
4	DThe producer is the green plant. The Sun is the energy source, not an organism in the chain.	1
5	AThe flea benefits and the host is harmed.	1
6	CThe community of living things plus the place and factors they share make the ecosystem.	1
7	DBacteria and fungi break down dead organisms and waste so nutrients can be used again.	1
8	BThe word equation is carbon dioxide + water → glucose + oxygen, using light.	1
9	AConsumers depend on the producer, directly or along the chain.	1
10	CSpecies that needed the wetland may no longer be able to live there.	1

Section B: Structured questions[20 marks]

Question	Answer and marking points	Marks
1(a)	Waterweed [1]	1
1(b)	The transfer of energy to the next organism. Energy transfer to the organism the arrow points to [1]	1
1(c)	The chains are linked. The waterweed is eaten by two animals, and both the snail and the insect are eaten by the fish. The chains are linked / share organisms [1] One organism has more than one food or more than one feeder [1]	2
1(d)	The snail and the insect lose their food, so their numbers fall, and the fish may then have less food. Consumers lose their food / numbers fall [1] A reason linked to the chain [1]	2
	Total for Question 1	6
2(a)	Any two: temperature, water, acidity or alkalinity of the soil. Air, light and minerals are also abiotic if named from the scene. First abiotic factor [1] Second abiotic factor [1] Do not accept grass or insects.	2
2(b)	Any one: deep roots; a thick waterproof surface; small leaves; storing water. A valid adaptation to scarce water [1]	1
2(c)	The insects are biotic, because they are living. The temperature is abiotic, because it is non-living. Insects are biotic / living [1] Temperature is abiotic / non-living [1]	2
	Total for Question 2	5
3(a)	carbon dioxide + water → glucose + oxygen Carbon dioxide and water as reactants [1] Glucose and oxygen as products [1] Also accept light energy stated with the equation, but light is not a substance in the equation.	2
3(b)	Energy [1]	1
3(c)	Photosynthesis takes carbon dioxide in. Respiration releases carbon dioxide. Photosynthesis uses carbon dioxide [1] Respiration produces carbon dioxide [1]	2
	Total for Question 3	5
4(a)	Parasitism [1]	1
4(b)	Mutualism [1] Both benefit: the bird gets food and the buffalo is freed of ticks.	1
4(c)	Any linked pair: animals may lose food or be separated from it; light, temperature or water on the ground may change where trees are removed. An effect on feeding links [1] An abiotic factor that changes, such as light or temperature [1]	2
	Total for Question 4	4

— End of mark scheme —