Investigations with Venus Fly Traps
Students’ Sheet
Introduction
Charles Darwin called the Venus Fly Trap ‘one of the most wonderful plants in the world', because
of their ability to snap shut, trapping prey in their leaves. In this activity, you’ll carry out your own
investigations into how the plants ‘know’ when to snap the trap shut.
Venus Fly Traps come from the bogs of North and South Carolina in the US. They survive in soil
containing very little nitrogen where regular wild fires burn other plants to the ground. In the wild,
they dug up by poachers who then sell them illegally. They are becoming an endangered species.
Investigation – Does a Venus Fly Trap know when to close?
Venus Fly Traps have traps to catch flies on the ends of flattened stems.
When these sense a fly, they snap shut, trapping it.
1. Examine the open traps on your plant. Look at the ‘spines’ on the edges of the traps.
2. Using a paintbrush, touch the spines as follows.
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


Touch 1 spine once and note the response.
Touch 1 spine twice in quick succession (e.g. 1 second)
Touch 1 spine twice with a longer interval (e.g. 30 seconds)
Touch 1 spine once and then another spine on the same side once.
Fill out the first four rows of the results table below.
Number of spines
touched
Number of times
each spine touched
Time interval between
touches (s)
1
1
1
2
1
2
2
1
1
30
1
Did the trap
close?
Q1: What do you conclude about the role of the spines in triggering the trap?
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Science & Plants for Schools: www.saps.org.uk
Investigations with Venus Fly Traps p.1
This document may be photocopied for educational use in any institution taking part in the SAPS programme.
It may not be photocopied for any other purpose. Revised 2010.
3. Now look for the trichomes (hairs).
Q2: How many are there on each side of the trap?
Q3: Is there the same number of trichomes in all traps?
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4. Using a paintbrush, touch the trichomes as follows.




Touch 1 hair once and note the response.
Touch 1 hair twice in quick succession (e.g. 1 second)
Touch 1 hair twice with a longer interval (e.g. 30 seconds)
Touch 1 hair once and then another hair on the same side once.
Fill out the first four rows of the results table below.
Number of trichomes
touched
Number of times each
trichome touched
Time between
touches (s)
1
1
1
2
1
2
2
1
1
30
1
Did the trap
close?
Q4: What do you conclude about the role of the trichomes in triggering the trap?
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5. Based on these initial results, decide what other experiments you could do in order to find
out what a Venus Fly Trap needs to close.
Don’t forget: you only have a limited number of traps and once they have closed they will
not reopen for a while. You need to plan your investigations carefully.
Carry your experiments out, and write the results in your results table above.
Q5: What are your final conclusions about what the trap needs to be triggered?
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Q6: Can you think of any evolutionary advantages for this behaviour?
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Science & Plants for Schools: www.saps.org.uk
Investigations with Venus Fly Traps p.2
This document may be photocopied for educational use in any institution taking part in the SAPS programme.
It may not be photocopied for any other purpose. Revised 2010.
Some extra things for you to consider:
Q1: Which control variables ensured a fair test?


Darwin’s own picture
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Q3: What was your dependent variable in your tests?
Q4: What were your independent variables?
Q5: Explain how reliable you think your data are
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Q6: Plant roots normally take up nitrogen from the soil. Insect bodies are a rich source of
nitrogen. What hypothesis (idea) could you suggest about why Venus fly traps needed to
develop a way of obtaining nutrients?
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Q7: See if you can illustrate your results in a chart
Q8: Can you name some other plants with adaptations to their environment?
Plant
Venus Fly Trap
Feature
Fly Traps
How it helps them to survive
Obtain nitrogen and other nutrients when they digest the insects
Science & Plants for Schools: www.saps.org.uk
Investigations with Venus Fly Traps p.3
This document may be photocopied for educational use in any institution taking part in the SAPS programme.
It may not be photocopied for any other purpose. Revised 2010.