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IB Biology SL C4.1.16 Predator Prey Relationships Questions

Predator and prey populations affect one another through density-dependent feedback. Snowshoe hare and lynx cycles show how changes in each population can occur with a time lag. Use population data to trace predator effects and the prey response.

Syllabus
First assessment 2025
Course
Biology SL
Level
SL

Exam points

  • Compare prey density with and without predators, and describe the population response after predator removal, including any delay or later reversal in the data.
  • Interpret predator–prey population trends and correlations, using prey availability and other ecological factors to judge whether predation explains the observed changes.

IB Biology SL C4.1.16 Predator Prey Relationships Questions question 1

[Maximum number: 2]

The sea snail Nucella ostrina and the sea star Pisaster ochraceus are predators of the mussel Mytilus trossulus. The mussels live on rocks at the edge of the sea and feed on phytoplankton and zooplankton. The zooplankton feed on the phytoplankton.

Nucella ostrina

Nucella ostrina

Pisaster ochraceus

Pisaster ochraceus

Mytilus trossulus

Mytilus trossulus

Groups of 50 mussels were transplanted to an experimental area and protected from predation until the start of the experiment. Researchers then investigated the effect of the predators on the population of the mussels over a period of 60 days.

Figure for Question IB Biology SL C4.1.16 Predator Prey Relationships Questions question 1 — IB Biology SL

Compare and contrast the effects of the predators on the population of the mussels.

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