CAIE IGCSE Biology 19.2 Food chains & food webs Question Bank
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
Practise food-chain and food-web questions by naming trophic roles, interpreting pyramids and explaining energy losses between trophic levels.
The diagram shows a food web.

What do the arrows represent?
the absorption of oxygen
the absorption of water
the flow of energy
the release of carbon dioxide
C
Coral reefs are important ecosystems.
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
State the number of secondary consumers shown in Fig. 6.2.
4 ;
State the name of a species that feeds at more than one trophic level in Fig. 6.2.
(reef) shark ;
State the number of different organisms in the shortest food chain in Fig. 6.2.
4 ;
State the evidence from the food web in Fig. 6.2, that phytoplankton are producers.
no arrows pointing to phytoplankton / AW ;
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.
any three from:
1 idea that energy transfer along a food chain is inefficient ;
2 and 3 named examples of causes of inefficient energy flow between trophic levels ;;
4 energy to, decomposers / decomposer food chain(s) ;
5 limited / not enough, energy to support another trophic level ;
A student recorded the information about an aquatic habitat.
Fig. 4.1 shows the student's notes.

Fig. 4.1
Construct a food web to show the feeding relationships described in Fig. 4.1.
Do not draw the organisms.
aquatic plants → midges → stoneflies → salmon → herons ;
aquatic plants → mayflies → salmon → herons ;
aquatic plants → freshwater shrimps → salmon → herons ;
all arrows drawn correct way from food to feeder and no additional wrong links and drawn as a food web ;

Official food-web answer
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

Completed Table 4.1
Outline how the energy in the primary consumers in this aquatic food web is used to produce biomass in the secondary consumers.
any three from:
primary consumers (tissues) contain chemical energy ; energy is transferred to, secondary consumers / predator (from primary consumers / prey, that are eaten) ; ora (named) food particles (of primary consumer) are digested (to make energy / glucose, available for respiration) ; energy (released) is used for, growth / to make, more / new / larger, cells / mitosis ; energy is used for, protein synthesis / reproduction / assimilation / storage as fat / storage as glycogen ;
Humans also eat salmon.
Predict the impact on the feeding relationships shown in Fig. 4.1 of overharvesting of salmon.
any three from:
fewer herons (as less, food / salmon) ;
more, mayflies / stoneflies / (freshwater) shrimps (as less salmon to eat them) ;
fewer midges (as more stoneflies) ;
fewer/more, no change in, aquatic plants (as more, mayflies / freshwater shrimps / fewer midges, feeding on them) ;
Describe what is meant by the term decomposer.
(organism) that gets its energy, from dead / waste organic, material ;
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.
any four from:
as fewer trophic levels / plants are at a lower trophic level (than salmon / livestock) ; ora
idea that energy transfer along food chain is inefficient ; (energy lost in) respiration / heat / (named) metabolic process / movement / muscle contraction ; ref to (more) material that is lost as, faeces / egested / inedible / not digestible (in longer food chains) ; (energy lost in) excretion / urine ;