IB ESS HL 4.4.14 Biotic Index Question Bank
Calculate and interpret a biotic index from aquatic invertebrate evidence.
- Syllabus
- First assessment 2026
- Course
- ESS HL
- Level
- HL
Exam points
- identify the aquatic-system process or pollution indicator
- apply the relevant conservation, quality or management model
- evaluate ecological and human trade-offs from evidence
4.4.14 (HL)—Biotic index question 1
[Maximum number: 7]
Describe methods that could be used to assess the impact of an industrial effluent on the biotic index of a river.
a. Identify sites at intervals upstream and downstream from point of effluence;
b. Take sufficient samples to be statistically significant;
c. Lay down a quadrat on river bed;
d. Hold net downstream of quadrat;
e. Kick/disturb substrate in quadrat;
f. Empty net contents into tray;
g. Identify different species using identification key or similar;
h. Estimate abundance of tolerant and sensitive species;
i. Return all invertebrates to sample site; j. Use data to calculate Biotic Index; k. Compare biotic indices upstream and downstream of effluence;
Note to examiners: Do not credit methods for direct measurement of pollution, BOD or Simpsons index - Q specifically addresses biotic index.
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