Live Earthworm Behavior Purpose - yayscienceclass

Live Earthworm Behavior

Purpose

Infer how physical and behavioral characteristics of the earthworm reflect adaptations to its

environment

Describe how an earthworm responds to light, moisture, surfaces, and gravity

Materials

paper towels water clock

red cellophane blue cellophane live earthworm

sandpaper foam mat light source

dissecting pan hand lens

Procedure:
1. Moisten a paper towel and place it in a dissecting pan. Watch the worm move and notice
which end leads. The worm's leading end is its anterior end. Identify the worms
posterior end, the end away from the leading end. Diagram the worm in your lab
notebook. Noting the posterior and anterior ends.
2. To differentiate between the worm's dorsal (back) and ventral (stomach) sides, roll the
worm over. Note the sides in your diagram and also describe the worm’s response to
being put ventral side up.
3. Notice how the body of the earthworm is divided into segments. Starting at about
segment number 32,there is a thickening in the body, called the clitellum, as shown in the
diagram below. The c1itellum produces a mucus sac in which the earthworm deposits its
eggs.

4. Using bristles called setae, located on its ventral surface and sides, the worm moves
through the soil. Setae give the worm traction. Use a hand lens to examine the worm's
body and locate the setae. You can also use your fingers to locate the setae by touch.
Answer in your lab notebook: How many pairs of setae are on each segment?

5. To determine if the earthworm is sensitive to light, cover the dissecting pan half with red
cellophane and half with the foam mat. Repeat for 2 more trials. Create a table in your lab
notebook like the one on the next page and record your data.

6. Replace the red cellophane with blue and repeat the above experiment.
7. Using construction paper, block the light so that it shines only on the worms anterior end.

Repeat 2 times and record your observations. Now, block the light so that it only shines
on the worm's middle. Then, block the light so it only shines on it's posterior.
Answer in your lab notebook: How might light sensitivity be an adaptation to the
earthworm's way of life?
8. To determine whether an earthworm prefers moist or dry environments, place a dry paper
towel next to the wet one. Place your worm across the two towels, as shown in the
diagram below.
Record in your lab notebook: Does your worm move toward the wet towel or the dry
towel? Why?

9. Place a piece of sandpaper next to the dry towel. Place the worm across the two surfaces,
anterior end on the sandpaper first. Observe the worm's response. Then place the worm
across the sandpaper and dry towel, this time with the anterior end on the towel. Record
your observations in your lab notebook.

10. Look carefully along the dorsal side of the worm. You will see a thick purple line running
down the entire length. This is the dorsal aorta, the major blood vessel of the worm.
Observe the dorsal aorta through the hand lens. Look for rhythmic contractions of the
dorsal aorta. Each ripple of contractions represents a single heartbeat. Determine the heart
rate by counting the number of ripples that occur in one minute. Repeat 2 times and
average. Record the two numbers and your average in your lab notebook.

11. Place one end of the dissecting pan on a book to create an incline. Place the worm in the
center of the pan with the anterior end toward the raised end ofthe pan. Wait 3 minutes
and record whether the worm has move to the raised or lowered end of the pan. Repeat 2
times and record your results.

12. Check an earthworm's "robin response". Gently grab your earthworm's anterior end as a
robin would if it were eating it. Describe the experiment and results in your lab notebook.

13. Return your earthworm to its container, and your cleaned materials to the appropriate
place.

1. Replace the red cellophane with blue and repeat the above experiment.
2.

Analysis Questions
1. Are there any areas of the earthworm's body more sensitive to light than other areas?
Which ones?
2. Which kind of surface, sandpaper or dry paper towel, does the worm prefer? Why do you
think it prefers that surface?
3. From the class totals, which stimulus seems to be stronger in forcing a response in
earthworms, light or gravity? Why?
4. Describe the relationship between heart rate and temperature in an earthworm.
5. What is the adaptive advantage to the earthworm's response to light and moisture?
6. What is the adaptive advantage of the earthworm's variations in hearth rate as
temperature is varied?
7. After a few weeks of drought, the ground may be dug up and no earthworms may be
found. After a few days of rain the earthworms are seen on the road and sidewalk
surfaces, even during daylight. Suggest reasons to explain this behavior based on what
you have learned.
8. Design an experiment to test the reaction of earthworms to differences in temperature.
(state your IV, DV, controls etc. and explain briefly what you would do)

9. Copy or glue the above diagram in your lab notebook.
10. You want to plant a garden in your backyard and are concerned about finding the best

place for it. You want to plant tomatoes and beans and know they do better in soil with
earthworms in it. The above is a diagram of your backyard that you made showing where
all the really wet and dry spots are as well as the kind of soil found there. Based on your
knowledge of earthworms, where would be the best place to plant your garden?
Use a pen or pencil and draw your garden into the above diagram.
11. Explain why you chose the area you did. Use data from your research to explain.