RP10 Taxis and kinesis using a choice chamber Questions

Specification route: RP10
Question bank: 12 questions
Course stage: Year 13 / A-level only

Sample questions

QUESTION 1 · RP10 · LEVEL 3

In a choice chamber experiment investigating the response of woodlice to humidity, what is the appropriate statistical test to analyse the final distribution data?

Chi-squared test
Student's t-test
Spearman's rank correlation coefficient
Standard deviation

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The data collected is categorical (counting the *number* of individuals in the 'dry' category vs the 'damp' category).

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Answer: Chi-squared test

Required practical 10. The chi-squared test is used to compare observed frequencies (the number of woodlice in each section) with expected frequencies (e.g., an even split) for categorical data.

QUESTION 2 · RP10 · LEVEL 3

In a choice chamber experiment with woodlice, why is a layer of gauze or mesh placed between the environmental substrates (like wet paper towel or silica gel) and the animals?

To act as a physical barrier so the woodlice are responding to the humidity in the air rather than direct tactile contact with the water or chemicals.
To provide a highly nutritious food source for the woodlice during the long experiment.
To deliberately slow down the movement of the woodlice so they can be counted easily.
To prevent the woodlice from mating during the observation period.

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You are testing their response to humidity (water vapor), not their response to walking on a puddle.

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Answer: To act as a physical barrier so the woodlice are responding to the humidity in the air rather than direct tactile contact with the water or chemicals.

Required practical 10. The mesh ensures that the independent variable is solely the atmospheric humidity/chemical gradient, preventing confounding tactile variables (like touching wet paper or toxic silica gel).

QUESTION 3 · RP10 · LEVEL 2

In a choice chamber experiment investigating humidity, one side contains wet paper towels and the other contains anhydrous calcium chloride (or silica gel). What is the purpose of the anhydrous calcium chloride?

It acts as a desiccant, absorbing water vapour from the air to create a strictly dry environment on that side of the chamber.
It provides an alternative food source for the woodlice to test their chemical preferences.
It releases a toxic gas that creates a negative taxis response.
It absorbs the carbon dioxide produced by the woodlice to prevent suffocation.

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Anhydrous means 'without water'. It is highly eager to absorb moisture.

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Answer: It acts as a desiccant, absorbing water vapour from the air to create a strictly dry environment on that side of the chamber.

Required practical 10. To test the effect of humidity, a clear gradient is needed. Silica gel or anhydrous salts actively remove moisture from the air, ensuring the 'dry' side remains strictly dry.

QUESTION 4 · RP10 · LEVEL 2

After introducing the woodlice into the centre of the choice chamber, the student waits $10$ minutes before recording their positions. Why?

To allow the woodlice time to recover from the stress of handling and to fully explore the chamber before choosing their preferred environment.
To give the woodlice enough time to reproduce and increase the sample size.
Because the humidity gradient takes exactly $10$ minutes to form inside the chamber.
To allow time for any mutated woodlice to die off naturally.

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Animals behave erratically when frightened or suddenly dropped into a new place.

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Answer: To allow the woodlice time to recover from the stress of handling and to fully explore the chamber before choosing their preferred environment.

Required practical 10. A waiting period allows the animals to habituate to the new environment and resume normal kinetic behaviour, ensuring the final distribution reflects their environmental preference rather than panic.

QUESTION 5 · RP10 · LEVEL 1

When using a choice chamber to investigate the response of woodlice to humidity, how is the 'dry' side of the chamber typically established?

By placing a desiccant, such as anhydrous calcium chloride or silica gel, in the base of that side to absorb moisture from the air.
By actively heating that side of the chamber with a Bunsen burner.
By placing dry paper towels on that side, which magically repel water vapour.
By completely vacuum-sealing that half of the chamber.

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You need a chemical that actively pulls water out of the surrounding environment.

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Answer: By placing a desiccant, such as anhydrous calcium chloride or silica gel, in the base of that side to absorb moisture from the air.

Required practical 10. To create a strict humidity gradient, the damp side uses damp paper towel, and the dry side uses a drying agent (desiccant) like anhydrous calcium chloride or silica gel to remove atmospheric water vapour.

QUESTION 6 · RP10 · LEVEL 2

Why must the woodlice be introduced into the choice chamber through a central hole, exactly on the boundary between the two conditions?

To ensure they start exactly halfway between the conditions, giving them a completely unbiased choice of which direction to travel.
To prevent them from immediately escaping the chamber.
To force them to drop directly into the desiccant to test their survival skills.
Because the central hole is the only place large enough to fit a woodlouse.

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If you put them all on the dry side to start with, it might just take them a long time to accidentally wander to the wet side.

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Answer: To ensure they start exactly halfway between the conditions, giving them a completely unbiased choice of which direction to travel.

Required practical 10. Introducing animals into the centre prevents starting bias. It ensures all individuals have an equal opportunity to sense both environments and make an active 'choice'.

QUESTION 7 · RP10 · LEVEL 2

If you are using a choice chamber to investigate the effect of humidity on maggots, why must the entire chamber be kept in a uniform, dim light or complete darkness?

Light is a confounding variable; maggots are negatively phototactic, so uneven lighting would influence their movement and invalidate the humidity results.
Maggots undergo rapid metamorphosis into flies if exposed to bright light.
Bright light actively destroys the silica gel, preventing the dry side from working.
The humidity gradient can only form in the absence of light energy.

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A fair test only has one independent variable.

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Answer: Light is a confounding variable; maggots are negatively phototactic, so uneven lighting would influence their movement and invalidate the humidity results.

Required practical 10 / PS 2.4. When testing humidity (the independent variable), all other abiotic factors that affect behaviour (like light intensity and temperature) must be tightly controlled.

QUESTION 8 · RP10 · LEVEL 2

After setting up the choice chamber and adding the animals, why do you wait 10 minutes before recording their final positions?

To allow the animals time to habituate to the new environment, recover from handling stress, and fully explore the gradient.
Because it takes exactly 10 minutes for the desiccant to begin absorbing water.
To give the animals time to undergo a cycle of aerobic respiration.
To see how many animals naturally die of old age before the experiment begins.

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Animals placed in a new box will usually scramble around randomly in panic for a few minutes.

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Answer: To allow the animals time to habituate to the new environment, recover from handling stress, and fully explore the gradient.

Required practical 10. A waiting period is essential so the animals can settle down from the stress of being moved and have enough time to actually experience both sides of the chamber before settling.

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