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IB Biology HL 4.1.16 Predation and foraging evidence Question Bank

Practise IB Biology HL 4.1.16 by analysing predator foraging data and ecological effects across populations.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • Interpret foraging data to test whether predator behaviour depends on prey density.
  • Evaluate how predation changes distributions, resistance and population outcomes.

C4.1.16—Predator-prey relationships question 1

[Maximum number: 3]

The shore crab (Carcinus maenas) forages for food in the intertidal zone on rocky seashores. An experiment was carried out to assess predation at specified levels of food abundance. An area of shore was enclosed in a wire cage. All other food was removed from the encaged area except the mussels provided by the investigators. The number of mussels consumed was measured while the crabs foraged at densities of one, two or four crabs per cage.

Figure for Question C4.1.16—Predator-prey relationships question 1 — IB Biology HL

Question (a)

(a)

Suggest a reason for the plateau in the graph when only one crab is present in the cage.

[ 1 ]

Question (b)

(b)

Determine whether foraging by crabs is dependent on number of prey (mussels) or number of predators (crabs).

[ 2 ]
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