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IB Biology HL 4.1.17 Top-down and bottom-up control Question Bank

Practise IB Biology HL 4.1.17 by analysing mesocosm evidence for trophic and nutrient control.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • Distinguish top-down and bottom-up control in community data.
  • Evaluate how predators and nutrients produce indirect effects across a food web.

C4.1.17—Top-down vs. bottom-up control question 1

[Maximum number: 3]

An investigation into food web interactions was conducted in mesocosms in the Mediterranean Sea, off the coast of France. The effects of the addition of soil and fish on bacterial populations were tested.

Figure for Question C4.1.17—Top-down vs. bottom-up control question 1 — IB Biology HL
Figure for Question C4.1.17—Top-down vs. bottom-up control question 1 — IB Biology HL

Question (a)

(a)

Assuming that the populations of bacteria are under bottom-up control, identify the mesocosms in which the bacterial populations will be highest.

[ 1 ]

Question (b)

(b)

Outline top-down effects on the bacteria in the four mesocosms.

[ 2 ]
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