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CAIE IGCSE Biology 19.2 Food Chains and Food Webs Questions

Practise food-chain and food-web questions by naming trophic roles, interpreting pyramids and explaining energy losses between trophic levels.

Syllabus
2026–2028
Course
Biology 0610

Exam points

  • construct and interpret food chains with arrows from food to feeder, beginning with a producer
  • construct food webs, trace connected prey and predators, and predict linked population changes
  • identify producer, consumer and decomposer roles from feeding and organic-material evidence
  • label primary to quaternary consumers and trophic levels from feeding links and pyramids
  • recognise organisms feeding at multiple trophic levels and count named levels or consumers
  • draw and interpret pyramids of numbers or biomass, including bars, labels and missing values
  • explain when biomass represents a food chain better than numbers for large and small organisms
  • interpret energy pyramids and identify the greatest-energy trophic level at the base
  • calculate energy transferred, lost or the percentage transfer between adjacent trophic levels
  • explain energy losses through respiration, heat, movement or waste and why higher levels support less
  • compare energy pyramids with number or biomass pyramids using time and organism-size evidence
  • explain why eating crops directly is more efficient than eating crop-fed livestock

Covered syllabus points

19.2.1—Food chain as showing the transfer19.2.2—Construct and interpret simple food19.2.3—Food web as a network19.2.4—Producer as an organism that makes its19.2.5—Consumer as an organism that gets its19.2.6—Consumers may be classed as primary19.2.7—Herbivore as an animal that gets its19.2.8—Carnivore as an animal that gets its19.2.9—Decomposer as an organism that gets19.2.10—Food chains and food webs to describe19.2.11—Pyramids of numbers and pyramids19.2.12—Pyramids of biomass19.2.13—Trophic level as the position19.2.14—Following as the trophic levels19.2.15—Pyramids of energy19.2.16—Pyramids of energy19.2.17—Transfer of energy from one trophic19.2.18—Explain, in terms of energy loss, why19.2.19—It is more energy efficient for humans

Question 1

[Maximum number: 1]

The diagram shows a food web.

Figure for Question 1 — CAIE IGCSE Biology

What do the arrows represent?

A

the absorption of oxygen

B

the absorption of water

C

the flow of energy

D

the release of carbon dioxide

Question 2

[Maximum number: 7]

Coral reefs are important ecosystems.

Question (a)

(a)

Fig. 6.2 is part of a food web for a coral reef ecosystem which is similar to the one shown in Fig. 6.1.

Fig. 6.2

Fig. 6.2

[ 7 ]

Question (i)

(i)

State the number of secondary consumers shown in Fig. 6.2.

[ 1 ]

Question (ii)

(ii)

State the name of a species that feeds at more than one trophic level in Fig. 6.2.

[ 1 ]

Question (iii)

(iii)

State the number of different organisms in the shortest food chain in Fig. 6.2.

[ 1 ]

Question (iv)

(iv)

State the evidence from the food web in Fig. 6.2, that phytoplankton are producers.

[ 1 ]

Question (v)

(v)

It is rare for there to be more than five trophic levels in an ecosystem.

Explain what limits the number of trophic levels in food webs.

[ 3 ]

Question 3

[Maximum number: 18]

Question (a)

(a)

A student recorded the information about an aquatic habitat.
Fig. 4.1 shows the student's notes.

Fig. 4.1

Fig. 4.1

[ 13 ]

Question (i)

(i)

Construct a food web to show the feeding relationships described in Fig. 4.1.

Do not draw the organisms.

[ 4 ]

Question (ii)

(ii)

Complete Table 4.1 using the information in Fig. 4.1 by identifying the names of the missing trophic levels and one organism at each different trophic level.

Table 4.1

Table 4.1

[ 3 ]

Question (iii)

(iii)

Outline how the energy in the primary consumers in this aquatic food web is used to produce biomass in the secondary consumers.

[ 3 ]

Question (iv)

(iv)

Humans also eat salmon.

Predict the impact on the feeding relationships shown in Fig. 4.1 of overharvesting of salmon.

[ 3 ]

Question (b)

(b)

Describe what is meant by the term decomposer.

[ 1 ]

Question (c)

(c)

Animals such as salmon can be farmed for meat.

Explain why it is more energy efficient for humans to eat crop plants than to eat livestock that have been fed on crop plants.

[ 4 ]
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