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IB Biology SL C3.1 Integration of Body Systems Questions

Practise IB Biology SL C3.1 by tracing reflex arcs, interpreting brain and organ-coordination evidence, and explaining hormonal and feedback control in the body.

Syllabus
First assessment 2025
Course
Biology SL
Level
SL

Exam points

  • Explain how interacting cells, organs, and systems produce coordinated or emergent properties, including hierarchical organisation.
  • Interpret digestive-organ diagrams and blood or duct pathways linking the liver, pancreas, gall bladder, and small intestine.
  • Identify hypothalamus, cerebellum, and medulla roles from brain diagrams, including appetite, coordination, balance, and involuntary control.
  • Interpret fMRI, pupil-reflex, decision-making, or contralateral-vision evidence to explain brain information integration.
  • Trace a pain-withdrawal reflex from receptor through sensory, relay, and motor neurons to a skeletal-muscle effector.
  • Relate melatonin, appetite signals, or pituitary hormones to circadian timing, feeding, or endocrine feedback.
  • Explain heart-rate control by medulla signals, autonomic nerves, adrenaline, and sinoatrial-node activity.
  • Explain CO₂/pH feedback from chemoreceptors through the medulla to ventilation and respiratory muscles.
  • Distinguish enteric control of involuntary peristalsis from CNS control of swallowing or egestion.

Covered syllabus points

C3.1.1—System integrationC3.1.2—Hierarchy in multicellular organismsC3.1.3—Integration of organsC3.1.4—Brain as information integration organC3.1.5—Spinal cordC3.1.6—Input through sensory neuronsC3.1.7—Output through motor neuronsC3.1.8—Nerves as bundlesC3.1.9—Pain reflex arcsC3.1.10—Cerebellum roleC3.1.11—Melatonin and sleepC3.1.12—Epinephrine (adrenaline)C3.1.13—Hypothalamus and pituitary controlC3.1.14—Heart rate feedback controlC3.1.15—Ventilation rate feedback controlC3.1.16—Peristalsis control

Question 1

[Maximum number: 3]

The diagram shows a biofilm that has formed on a tooth.

Figure for Question 1 — IB Biology SL

Using the diagram, explain the concept of emergent properties of biofilms.

Question 2

[Maximum number: 1]

Why do multicellular organisms have emergent properties?

A

They have more genes than unicellular organisms.

B

Properties of unicellular organisms are enhanced by having many cells.

C

All of their genes are expressed whereas unicellular organisms express only some.

D

They show properties that can only result from the interaction of many cells.

Question 3

[Maximum number: 2]

Draw a labelled diagram showing the interconnections between the liver, gall bladder, pancreas and small intestine.

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