IB Biology HL C4.1.17 Top Down Vs Bottom Up Control Questions

Top-down control begins with predators and can cascade to lower trophic levels. Bottom-up control begins with producers or resources and affects higher trophic levels. Use food-web, mesocosm and nutrient data to trace these effects.

Exam points

Trace top-down control from predators or consumers through a food web to lower trophic levels, including indirect effects on producers.
Trace bottom-up control from producer or resource changes to higher trophic levels, and distinguish it from predator-driven effects in ecological data.

[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.

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(a)

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

[ 1 ]

(b)

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

[ 2 ]

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IB Biology HL C4.1.17 Top Down Vs Bottom Up Control Questions question 1

Question (a)

Question (b)