Question bank › IGCSE Biology › Ecology and the environment

Food chains, food webs, pyramids and energy transfer

Answer on paper first, then reveal the mark scheme one mark at a time.

1Grade 1–33 marks

Here is a food chain.

grass → rabbit → fox

(a) Name the producer. [1]

(b) Name the secondary consumer. [1]

(a) grass(1)
(b) fox(1)
(c) the transfer / flow of energy (from one organism / trophic level to the next); allow transfer of biomass / food / nutrients; ignore 'is eaten by' on its own(1)
Answer: (a) grass (b) fox (c) energy transfer
Examiner tip: The arrow points in the direction energy flows — towards the organism doing the eating.

2Grade 6–74 marks

The table shows the energy in each trophic level of a grassland ecosystem.

(a) Calculate the percentage of energy transferred from the producers to the primary consumers. [2]

(b) Explain why only a small percentage of energy is transferred from one trophic level to the next. [2]

(a) 1890 ÷ 21 000 × 100(1)
(a) 9 (%); accept 9.0 / 9.00; correct answer with no working scores 2(1)
(b) any two from: energy lost as heat from respiration; energy used for movement; energy lost in faeces / not all food is digested / egested; energy lost in urine / excretion; not all parts of the organism are eaten (e.g. roots, bones); not all organisms are eaten — first point(1)
(b) second point; ignore 'energy used up' unqualified(1)
Answer: (a) 9% (b) energy lost as heat from respiration; not all parts eaten / lost in faeces
Examiner tip: 'Energy is used up' is too vague — say it is lost as HEAT from respiration or in faeces.

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