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IB ESS SL 2.1.23 Keystone Species Questions

Practise IB ESS SL 2.1.23 by explaining how keystone species regulate food webs, biodiversity and ecosystem resilience through examples such as elephants, sea otters and wolves.

Syllabus
First assessment 2026
Course
ESS SL
Level
SL

Exam points

  • explain why a named species is keystone by linking population control to community structure and sustainability
  • predict trophic cascades after removing elephants, sea otters or wolves, including habitat and biodiversity loss
  • explain how keystone species increase resilience through population regulation, productivity and complex food webs
  • justify whether losing a large or keystone species is a significant ecosystem loss using biodiversity evidence

Learn this topic

Study 2.1.23—Keystone species conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

IB ESS SL 2.1.23 Keystone Species Questions question 1

[Maximum number: 4]
Figure A simplified food web in a kelp forest ecosystem

Figure A simplified food web in a kelp forest ecosystem

Figure Kelp forest ecosystems with and without the presence of sea otters

Figure Kelp forest ecosystems with and without the presence of sea otters

The arrows indicate the flow of carbon between the atmosphere and the carbon stored in kelp.

Question (a)

(a)

Outline why sea otters are considered a keystone species.

[ 1 ]

Question (b)

(b)

Explain how sea otters contribute to the resilience of the kelp forest ecosystem.

[ 3 ]
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