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IB Biology HL D4.2.9 Biomagnification Questions

Trace retained toxins through food chains, explain their increasing concentration in consumers, and apply DDT and mercury evidence to effects on predators.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • Define biomagnification as an increase in pollutant concentration at successive trophic levels.
  • Explain how retained toxins pass from contaminated prey to consumers and become more concentrated at higher trophic levels.
  • Use a named DDT or mercury example to link high trophic-level exposure to a harmful effect on a consumer.
  • Use trophic-level mercury data to identify lower-risk fish and explain how feeding choices affect contamination risk.
  • Justify a predator’s high DDT concentration from food-web links, toxin retention and trophic-level magnification.

IB Biology HL D4.2.9 Biomagnification Questions question 1

[Maximum number: 2]

The diagram shows levels of DDT, a pesticide, in an aquatic food web in Lake Kariba, Africa. Numbers represent ppm (parts per million) of DDT in fat tissue.

Figure for Question IB Biology HL D4.2.9 Biomagnification Questions question 1 — IB Biology HL

Justify the observation that the crocodile has a higher mean DDT level than the cormorant or tigerfish.

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