IB ESS HL 4.4.14 Hl Biotic Index Questions
Calculate and interpret a biotic index from aquatic invertebrate evidence.
- Syllabus
- First assessment 2026
- Course
- ESS HL
- Level
- HL
Exam points
- explain how a biotic index uses indicator organisms and community composition to assess pollution
- design sampling upstream and downstream, identify and count organisms, calculate an index and repeat sampling over time
- evaluate biotic indices against chemical measurements by comparing cost, ecological impact, combined pollutants, history and limitations
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IB ESS HL 4.4.14 Hl Biotic Index Questions 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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