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Topics  > Biology > Botany

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The materials required for the experiment:

-    1 packet of tomato seeds
-    1 packet of green bean seeds
-    1 packet of radish seeds
-    6 small plastic pots
-    Soil to fill 6 pots
-    30 earthworms
-    Tap water
-    1 measuring cylinder
-    Ruler (1 meter)


1.    For this experiment, the independent variable is whether or not the earthworms were present in the soil. The dependent variable is the height of the plants after 8 days. This is determined by using a ruler to measure the height of the 10 plants in each pot and calculating their average height. The constants (control variables) are the environment the plants are kept in (temperature, humidity, light, etc), the size of the pot, the type of plants (namely, tomato, green beans and radish) and the type of soil.

2.    The pots are labeled “tomato”, “green beans”, “radish”, “tomato-worm”, “green beans-worm” and “radish-worm”. The soil is inspected and any earthworms removed. The same amount of soil is filled into each pot. 10 earthworms are added in each of the 3 pots labeled with “worm”. 10 tomato, green bean and radish seeds are planted in each of the 6 pots according to the markings on the pot.

3.    The plants are watered once a day with the same amount of water and placed where they can get enough sunlight to grow.

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Complexity level:
Project cost ($):
Time required:
1 day to prepare, 8 days for observation
Material availability:
Look for earthworms in your garden. The seeds may be obtained from a nursery.
Safety concerns: