What can worms sense?

STAGE 1: Planning and Preparation

Essential knowledge

• Earthworms are tube-shaped, segmented animals that live underground. They feed on dead and organic matter.
• The common earthworm, Lumbricus terrestris, also known as the lob worm, is Britain's most common and longest earthworm.
• The earthworm has no eyes, yet they can tell light from dark. They have no ears, yet can sense the vibrations of sound. They have no nose, yet can smell and taste which foods to eat. The earthworm's skin provides a sense of touch.
• Although earthworms have no eyes, ears and nose, they have all the senses they need to move towards food, shelter and away from danger. For example, earthworms keep away from bright light to avoid drying out and stay clear of predators.
• When exposed to stimuli such as light, earthworms will either move away from the source of the stimulus or 'play dead'.

Pre-investigation tasks

1. Make your own earthworm habitat. Prepare a small container (plastic box or tray) by adding a layer of soil in the bottom. Collect a few leaves, moss and pieces of bark or twigs and add them to the container too. Use a spray bottle and water to make everything nice and damp. Now go on an earthworm hunt! Dig in the soil, collect any earthworms you find and put them into your new earthworm habitat.
2. Now wet a paper towel and lay it on your table (or patio!). Choose an earthworm from your habitat and put it on the paper towel. Can you describe what it looks like, feels like and how it moves? Take a photo or draw an image of your earthworm and write 3-5 labels about it. Normally, earthworms move with their head first – can you point to your earthworm's head? Use a phone or tablet camera to zoom in and have a really close look at the earthworm. Does it look wet or dry? Does it have any patterns on its skin? Think about things you'd like to know about earthworms. Write down your questions or ask a grown up to write them down for you.
3. Think about what senses we have. Which parts of our body give us our senses? Why are our senses important? Draw a picture of yourself this time and add in body part labels including which of the 5 senses those parts are useful for. Time to put your senses to the test. Follow the questions below to think deeper about what things YOU can sense!

• Can you see torchlight? (be careful not to look directly at a beam, just watch as it shines on your hand)
• Can you feel it when your skin is touched? How would you describe different kinds of touch?
• Can you hear a range of sounds in your house? Outside? What are they?
• Can you smell different scents? Are they pleasant or disgusting?

So, back to our investigation question:

What can worms sense?

• How could we find an answer? 
• How will we know if an earthworm can sense?
• How might the earthworm react?
• What might we look for in the investigation? 

During each test, remember to watch the earthworm closely, looking for and describing how they react.

PARENTS: Earthworms may stop responding during testing. Have extra earthworms available so that you can give your child a new one if this happens. If possible, work in a dimmed or darkened room. Always work with earthworms on a damp paper towel when are observing and testing please. Make sure they wash their hands thoroughly after they have touched and handled the earthworms too!

STAGE 2: Let's Investigate

Equipment

• Earthworm
• Tray with sides
• Damp paper towels or tissue
• Black card or paper
• Cotton buds
• Musical instruments, such as drum, tambourine, recorder or maracas
• Vinegar
• Method board (attached below)

Important question: Is your test kind?

Make sure you are gentle with the earthworms and don't cause them any harm .

Prediction

• Which senses do you think an earthworm has?
• Why do you think this?

Method

Test 1: sight

1. Lay damp paper towels in the bottom of the tray.
2. Cover half the tray with black construction paper to create a dark end.
3. Put an earthworm in the light end of the tray. What does the earthworm do?
4. Move the black paper to the other end of the tray. Put the earthworm in the light end again. What does it do? What does this tell you about its ability to sense light?

Test 2: touch

1. Use a clean cotton bud to gently tickle the earthworm in different places. Tickle its head, tail, back and tummy.
2. Watch what the earthworm does when you tickle in different places. What does this tell you about its sense of touch?

Test 3: hearing

1. Gently tap the tray in a place near the earthworm. Now try clapping – start quietly and get louder.
2. Play instruments at different volumes near to the earthworm. Does it react to any of the sounds? What does this tell you about an earthworm's sense of hearing?

Test 4: smell

1. Dip a cotton bud in vinegar and hold it near to the earthworm's head – but don't touch it! Does it react to the smell?
2. Put the cotton bud with vinegar near other parts of the earthworm's body and watch what it does. What does this tell you about its sense of smell?

Stage 3: Summarising Learning

Reflection

• Which sense you were testing in each test?
• Did you observe what the earthworm did in each test?
• Did you correctly identify whether it had the sense you were testing for?

Can you use modelling dough to make an earthworm to keep? Identify which ends are its head and tail and use your model to demonstrate how the earthworms reacted during each test. Perhaps you could write labels and captions on the piece of paper your earthworm is laying on.

Conclusion

How did you decide whether the earthworms could sense the different stimuli, such as light or sound? Compare humans with earthworms; think about how we may look and live differently, yet share common senses. Have a look back at our questions from the 3 pre-investigation tasks. Have we managed to answer any of the questions?

Final Questions

1. What tests did you do with the earthworms?

2. How did you know if the earthworm could see, feel, hear or smell?

3. Which senses do earthworms have and how do they compare to humans?

4. Why do earthworms need their senses?

5. Do you think the earthworms behave in the same way when they are in their normal habitat?

6. Can you think of ways that you could test to see if earthworms have a sense of taste?