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Date May 2019 Marks available 1 Reference code 19M.3.HL.TZ1.15
Level Higher level Paper Paper 3 Time zone Time zone 1
Command term Outline Question number 15 Adapted from N/A

Question

The illustration shows a Gersmehl diagram of the taiga biome.

[Source: adapted from P J Gersmehl]

Outline what is represented by the arrows in the Gersmehl diagram. 

[1]
a.

Explain how the amount of litter in a tropical rainforest would differ from the taiga’s and how this would be represented in a Gersmehl diagram.

[3]
b.

Markscheme

nutrient flow ✔

a.

a. the circle would be «relatively» smaller
OR
litter layer is less ✔

b. warmer weather favours the decomposition of litter/results in thicker arrow between litter and soil ✔

c. more rainfall favours the decomposition of litter/results in thicker arrow between litter and soil ✔

d. greater number of saprophytes/decomposers in rain forest ✔

e. nutrients would be stored in biomass/biomass circle would be larger ✔

b.

Examiners report

This question was not answered well. The answers indicated that Gersmehl diagrams are not covered in detail in many classes, as few students demonstrated the knowledge required to answer these questions. Many candidates confused “energy” with “nutrients.”

a.

The answers to this question showed a greater range of content knowledge than the answers to any other question. Students with no knowledge of the topic considered litter in this context to mean trash left by tourists. Weaker students who had studied some ecology assumed litter would be more in tropical rain forest simply because they felt more growth would occur in tropical climates. Medium-range students were able to score 2 marks regarding the size of circles, showing adequate understanding and some analysis. Students with a strong understanding of this topic in ecology commented on the role of decomposers as well.

b.

Syllabus sections

Option C: Ecology and conservation » Option C: Ecology and conservation (Core topics) » C.2 Communities and ecosystems
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Option C: Ecology and conservation » Option C: Ecology and conservation (Core topics)
Option C: Ecology and conservation

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