IB Diploma Biology chapter 3: C Interaction and interdependence MCQs with answers

By Team Megalecture · Updated 4 Nov 2026

96 exam-style questions on C Interaction and interdependence, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.

96 questions · 8 topics · 10 per test

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What chapter 3 covers

Ten C Interaction and interdependence questions with answers

Try each one, then open the answer. These ten stay the same; the test draws new ones every time.

1. Which group of organisms contains no species known to cause disease in humans?

  1. A
    protists, mostly unicellular eukaryotes with a nucleus
  2. B
    bacteria, prokaryotes whose cell walls contain peptidoglycan
  3. C
    archaea, prokaryotes whose cell walls contain no peptidoglycan
  4. D
    fungi, eukaryotes whose cell walls contain chitin
Show answer

Answer: C. Pathogens include viruses, bacteria, fungi and protists. No archaeon is known to cause any disease in humans.

2. An impulse travels 0.60 m along an axon in 20 ms. What is the speed of conduction?

  1. A
    300 m s−1
  2. B
    30 m s−1
  3. C
    0.03 m s−1
  4. D
    12 m s−1
Show answer

Answer: B. Speed = distance ÷ time = 0.60 m ÷ 0.020 s = 30 m s−1. Using 20 without converting milliseconds to seconds gives the wrong 0.03.

3. The action spectrum of a plant has peaks at about 430 nm and 660 nm and a trough at about 550 nm. What is the best explanation of the trough?

  1. A
    green light is fully absorbed by carotene, which cannot pass the energy on to the photosystems in the chloroplast
  2. B
    green light has too little energy to raise electrons in any pigment, so it can never be absorbed by chloroplasts
  3. C
    the stomata of a leaf close in green light, so almost no carbon dioxide can enter for the light-independent reactions
  4. D
    the pigments absorb little green light, which is mostly reflected or transmitted, so little energy drives photosynthesis
Show answer

Answer: D. Chlorophylls absorb mainly blue and red light. Green light is mostly reflected or transmitted, so the rate of photosynthesis is lower there, which is why leaves look green.

4. Conduction speeds were measured in three fibres. A: myelinated, diameter 4 µm, 25 m s−1. B: non-myelinated, diameter 4 µm, 2 m s−1. C: non-myelinated, diameter 500 µm, 25 m s−1. Which conclusion is best supported?

  1. A
    conduction speed is determined by the sodium ion concentration outside the axon, because the three fibres were in the same fluid
  2. B
    both myelination and a larger axon diameter increase the speed of conduction
  3. C
    diameter has no effect on speed of conduction, because fibres A and C conduct at the same speed even though their diameters differ
  4. D
    myelin slows conduction compared with a non-myelinated fibre of the same diameter, because it insulates the axon
Show answer

Answer: B. A is much faster than B at the same diameter, so myelin increases speed. C is much faster than B despite having no myelin, so a wider axon also increases speed. Squid giant axons are an example.

5. In experiment 1, 1.0 g of liver released 36 cm3 of oxygen from hydrogen peroxide in 3 minutes. In experiment 2, 2.0 g of liver released 54 cm3 in 90 seconds. What was the mean rate in experiment 2, per gram of liver?

  1. A
    0.30 cm3 s−1 g−1
  2. B
    0.60 cm3 s−1 g−1
  3. C
    0.20 cm3 s−1 g−1
  4. D
    18 cm3 s−1 g−1
Show answer

Answer: A. Rate = 54 ÷ 90 = 0.60 cm3 s−1, and per gram this is 0.60 ÷ 2.0 = 0.30. 0.60 forgets to divide by the mass, 0.20 is the rate in experiment 1, and 18 is the value per minute per gram, wrongly labelled with seconds.

6. In a chromatogram of leaf pigments the solvent front moved 8.0 cm and one pigment spot moved 3.6 cm. What is the Rf value of the pigment?

  1. A
    0.45
  2. B
    4.4
  3. C
    0.55
  4. D
    2.2
Show answer

Answer: A. Rf = distance moved by the pigment ÷ distance moved by the solvent front = 3.6 ÷ 8.0 = 0.45. Rf can never be greater than 1; 0.55 is 1 − 0.45.

7. Which statement describes the energy conversion in photosynthesis and what later happens to the energy stored?

  1. A
    light energy is converted to chemical energy in carbon compounds, some of which is later released by respiration
  2. B
    light energy is converted to heat energy, which the plant stores in glucose as the kinetic energy of its molecules
  3. C
    light energy is converted to chemical energy in ATP only, because carbon compounds cannot store energy
  4. D
    chemical energy in glucose is converted to light energy, which is given off by the leaf as a by-product
Show answer

Answer: A. Photosynthesis traps light energy as chemical energy in organic compounds, which supply energy to producers and, through food chains, to consumers.

8. Why are natural ecosystems described as open systems?

  1. A
    only energy can enter and leave, because matter is recycled completely within the ecosystem
  2. B
    both energy and matter can enter and leave them
  3. C
    only matter can enter and leave, because energy is trapped by the producers inside it
  4. D
    neither energy nor matter can enter or leave, because ecosystems are self-contained units
Show answer

Answer: B. Energy enters as sunlight and leaves as heat; matter also crosses the boundary, for example through migration, water flow and the atmosphere. A closed system exchanges energy but not matter.

9. A child is infected with a virus and recovers. Later the child is exposed to the same virus. Which observation would show that the adaptive immune system is at work?

  1. A
    the second infection is cleared much faster, because memory cells specific to that virus were made in the first
  2. B
    the second infection is cleared faster, because the skin has become thicker since the first infection
  3. C
    the second infection produces more mucus, because goblet cells learned to recognize the virus
  4. D
    the second infection is cleared at the same speed, because phagocytes respond to every infection in the same way
Show answer

Answer: A. The adaptive system responds specifically to a particular pathogen and builds up a memory of it; the innate system gives the same broad response every time.

10. A person treads on a sharp object and lifts the foot before feeling any pain. Which is the correct sequence for this reflex?

  1. A
    pain receptor, interneuron in the spinal cord, sensory neuron, motor neuron, skeletal muscle
  2. B
    pain receptor, sensory neuron, interneuron in the spinal cord, motor neuron, skeletal muscle
  3. C
    pain receptor, motor neuron, interneuron in the spinal cord, sensory neuron, skeletal muscle
  4. D
    pain receptor, sensory neuron, cerebral cortex, motor neuron, skeletal muscle
Show answer

Answer: B. A sensory neuron passes the impulse to an interneuron in the spinal cord, which connects to a motor neuron that makes the muscle contract. Because the brain is not involved in the first step, the response is faster than a voluntary one.

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C Interaction and interdependence: questions students ask

How many C Interaction and interdependence MCQs are there?

96, each with the answer and a short explanation, across 8 topics: C1.1 Enzymes and metabolism, C1.2 Cell respiration, C1.3 Photosynthesis, C2.2 Neural signalling, C3.1 Integration of body systems, C3.2 Defence against disease, C4.1 Populations and communities, C4.2 Transfers of energy and matter. Every chapter test draws ten of them, so you can take it many times.

Is the IB Diploma Biology chapter 3 test free?

Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.

How is the chapter test marked?

The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.

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