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IB ESS SL 2.2 Energy and Biomass Question Bank

Practise IB ESS SL 2.2 by tracing energy through food webs, interpreting trophic data and explaining losses, bioaccumulation and biomagnification.

Syllabus
First assessment 2026
Course
ESS SL
Level
SL

Exam points

  • Draw energy-system diagrams showing stores, feeding transfers and photosynthesis or respiration transformations.
  • Interpret food-web arrows and trophic levels to predict indirect effects of species loss or human activity.
  • Estimate dry biomass and interpret pyramids of numbers, biomass or energy with suitable units.
  • Explain trophic energy losses through respiration, heat, uneaten material and incomplete absorption.
  • Distinguish bioaccumulation from biomagnification and explain threats to top consumers.

Covered syllabus points

2.2.1—Ecosystem sustenance2.2.2—First law of thermodynamics2.2.3—Energy and matter transformation2.2.4—Photosynthesis2.2.5—Producers2.2.6—Cellular respiration2.2.7—Heat generation2.2.8—Second law and energy loss2.2.9—Consumer energy sources2.2.10—Producers and food chains2.2.11—Food chains and trophic levels2.2.12—Food-chain energy losses2.2.13—Gross and net productivity2.2.14—Limits on trophic levels2.2.15—Food webs2.2.16—Biomass measurement2.2.17—Ecological pyramids2.2.18—Non-biodegradable pollutants2.2.19—Microplastics2.2.20—Human activity impacts

2.2 Energy and biomass in ecosystems question 1

[Maximum number: 3]
Figure: Example of a lake ecosystem

Figure:Example of a lake ecosystem

Figure: Example of a lake ecosystem below shows an example of a lake ecosystem.

Rooting flowering plants: producers

Question (a)

(a)

State the source of energy for this ecosystem.
(a) (i) State the source of energy for this ecosystem.

[ 1 ]

Question (b)

(b)

Identify one way in which energy may leave this ecosystem.

Birds: secondary and tertiary consumer eg kingfisher

Floating plants: producers eg lilies, water fern

Frog: secondary consumer

[ 1 ]

Question (c)

(c)

Draw a food chain from the ecosystem in Figure: Example of a lake ecosystem consisting of four trophic levels.

[ 1 ]

2.2 Energy and biomass in ecosystems question 2

[Maximum number: 7]

Compare and contrast the pathways of energy through the atmosphere and the pathways of energy through an ecosystem.

2.2 Energy and biomass in ecosystems question 3

[Maximum number: 11]

Question (a)

(a)

Outline the transfers and transformations of matter as it enters and flows through the first trophic level of a food chain.

[ 4 ]

Question (b)

(b)

Describe how the emissions from the combustion of fossil fuels may impact the productivity of terrestrial ecosystems.

[ 7 ]
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