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IB ESS HL 2.2 Energy and Biomass Question Bank

Practise IB ESS HL 2.2 by analysing energy budgets, trophic efficiency, biomass evidence and the movement of persistent pollutants through food webs.

Syllabus
First assessment 2026
Course
ESS HL
Level
HL

Exam points

  • Analyse energy stores, feeding transfers and transformations in ecosystem system diagrams.
  • Evaluate food-web structure and trophic efficiency when species or human pressures change.
  • Interpret biomass and energy pyramids, including units, sampling limits and anomalous data.
  • Evaluate energy losses from respiration, heat, uneaten material and incomplete absorption.
  • Analyse bioaccumulation and biomagnification evidence to assess risks 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 impacts2.2.21 (HL)—Autotrophs vs. heterotrophs2.2.22 (HL)—Photoautotrophs and chemoautotrophs2.2.23 (HL)—Primary productivity2.2.24 (HL)—Secondary productivity2.2.25 (HL)—NPP and food chains2.2.26 (HL)—Maximum sustainable yield2.2.27 (HL)—Lower trophic level yields2.2.28 (HL)—Ecological efficiency2.2.29 (HL)—Entropy in ecosystems

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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