worm lab handouts and update

We began the worm lab on Thursday 9-17-09. On that day we learned bout worms, made initial observations of the worms, measured them using the metric system, and drew them to scale 3X their true size.
This week we discussed the steps of the scientific method, made worm habitats, and finally added the worms yesterday. So Wednesday (9-23-09) was day zero for our experiments. We will be making worm observations on a weekly basis for the next couple of months until the lab is completed some time round thanksgiving.
The following were handouts that were used during the lab. If you missed the lab due to an excussed absence please talk to me about making up portions of it during lunch or after school.

Directions for earthworm lab, day 1.

1. Get a piece of paper towel about 20cm long and wet it with water.

2. Find a red wiggler in the worm bin.

3. Name the worm (First, middle, and your last name).

4. Measure the length to the worm in centimeters and millimeters.

5. Measure the diameter of the worm in mm.

6. Draw the worm magnified 3X. This means that if your worm is 6cm long you will draw it 3X 6cm = 18cm long.

7. Add details such as hearts, and the parts of the digestive tract.


Building an earthworm habitat
We have observed worms in class and most have observed them in the outdoors as well. Observation is the first step of the scientific method. An observation can be anything that you notice with your senses. Write three observations you have made about earthworms.
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2.
3.

Observations often lead to further questions such as:
What do worms eat?
How fast do they reproduce?
How do they affect the soil?
How fast do they change the soil?
These are all questions that we can answer through experimentation and observation. Do you think you know the answer to any of these questions?

If you have an explanation or educated guess for any of these that can be tested by experimentation then you have a hypothesis. Forming a hypothesis is the second step of the scientific method. Write a hypothesis for each of the questions above.
1.
2.
3.
4.

After you have made a hypothesis, make a prediction about what would happen if your hypothesis is correct.
1.
2.
3.
4.

Forming a hypothesis and making a prediction is the second step of the scientific method

Can you design an experiment to test one of the hypothesis?
An experiment is procedure designed to test a hypothesis.
Most good experiments have a control group and an experimental group.
Both groups are treated the same with one exception, the experimental group has a single thing that is different than the control group. The variable is the factor of interest that when changed help you test your prediction. There are two types of variables, the independent or manipulated variable and the dependent or responding variable. The independent variable is the thing that you have control over to change. The dependent variable is what changes because of the independent variable.
It might be possible to design an experiment that would take place in the worms natural environment or in the community garden but if we do it in the lab we can control variables much better and we can make more observations on a regular basis.
We can make a habitat for the earthworms that mimics their environment outdoors. We can then change parts of it to see how it affects the earthworms. Or we could design a habitat and then add earthworms to see how they change their habitat or environment.

Materials need:

Organic debris (surface litter)
Dirt
Paper
Leaves
Grass
Pine needles
Saw dust
food
Water
Worms
Large clear containers
Gallon jars
Fish tanks
2-3 liter pop bottles
Graduated cylinders
Metric ruler
Thick construction paper

Directions:
Keep notes of every step you do in setting up your experiment.
Decide how many earthworm habitats your class needs to make to test your hypothesis. Remember that you need at least one control and one experimental group. Make sure your control and experimental group are the same except for the dependent variable.
Build the habitat:
1. Put several layers of organic debris into your habitats approximately 1cm thick layers. For example, you could put one cm of dirt, then one cm of leaves, one cm of food, one cm of paper, etc…until you are within 2 cm of the top. If you want to be more precise, you could weigh the amount of each layer so that you know you are adding the same amount to each habitat. In your lab notebook, draw a picture of the habitat including labels of each layer.
2. You can compact the layers by pushing down on them with your hand. Unless the amount of compaction is the variable you plan to test, you should do this equally to all your habitats. If you do this record it in your lab notebook.
3. You then need to add water to the habitat so that it will be moist enough for the worms. To test drainage rate, you can record the amount of time that it take for the water to reach the bottom of the habitat. Record how much water you added to each habitat and how long it took to for it to reach the bottom.
4. Label the experimental and control groups so they will not become confused or mixed up.
5. Now add worms to your habitats. Record the amount of worms added to each habitat. If you are testing how worms affect their habitat then your control may not have any worms in it.
6. Take a picture of you habitats on day 0, when you begin the experiment.
7. Put the worm habitats in a dark place or cover them so they are not exposed to light.
8. Periodically, at least once per week, you need to make further observations and notes of the worm habitats to see how they are changing. You may want to take pictures to document this for the future. We will observe the worms for a couple of months and everyone should have weekly observations in their notebooks about how the habitats change.