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CAIE IGCSE Biology 19.2.11 Pyramids of Numbers & Biomass

Practise drawing and interpreting pyramids of numbers and biomass from food chains, organism counts and mass data.

Syllabus
2026–2028
Course
Biology 0610

Exam points

  • draw horizontal bars in trophic order using organism counts or biomass values
  • distinguish a pyramid of numbers from biomass when one large producer supports many consumers
  • explain narrower upper levels using energy loss and the smaller biomass they can support

19.2.11—Pyramids of numbers and pyramids question 1

[Maximum number: 3]

Question (a)

(a)

A scientist studied communities in different parts of a desert and estimated the biomass of the organisms in each area.

He divided the organisms into four groups according to their roles in the food web as shown in Table 2.1.

Detritivores are animals that eat dead organisms or parts of organisms.

Table 2.1

Table 2.1

Some of these results are shown as a pyramid of biomass in Fig. 2.2.

Fig. 2.2

Fig. 2.2

[ 3 ]

Question (i)

(i)

Use the information in Table 2.1 to complete the pyramid of biomass in Fig. 2.2.

[ 2 ]

Question (ii)

(ii)

The scientist observed the detritivores and decided to include them with herbivores in this pyramid of biomass.

Suggest what the scientist discovered about the detritivores that made him make this decision.

[ 1 ]
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