Background
Earthworms are classified under the Annelia phylum. Worms in this phylum differ from the other categories primarily because they have segmented bodies that have more specialized tissues and are hermaphrodites (an organism that has reproductive organs normally associated with both male and female sexes). During the initial observation, the worm did not move because it was called. When the worm is rolled on its dorsal side, it does not move for a few seconds and then attempts to roll itself back around. By observing the worm from the underside of the glass container, the segmented parts of the worm are visible and the outline of the digestive tract is slightly visible. The worm's behavior when it's touched is taxis. When it receives a stimulus, the worm it either moves towards or away the specific stimulus. The worm demonstrates kinesis when it attempts to move away from the light; it contracts its muscles when it tries to move from one side of the tray to the other.
Hypothesis and Procedure:
Hypothesis: Does the worm prefer wet soil to dry soil? Does the worm move away or stay in the direct light?
Procedure:
~ Obtain a dissecting tray to put the soil in
~ Pour the soil evenly into the tray (making sure to make a mark in the middle of the tray); one side for wet soil and one side for dry soil
~ Pour 100mL of water on the soil; mix the soil well
~ Place the worm in the middle of the two soil sections
~ Observe the worm's behavior
~ Once the worm's behavior has been observed, place a light over the tray
~ Turn it on and observe the worm's response to light
Procedure:
~ Obtain a dissecting tray to put the soil in
~ Pour the soil evenly into the tray (making sure to make a mark in the middle of the tray); one side for wet soil and one side for dry soil
~ Pour 100mL of water on the soil; mix the soil well
~ Place the worm in the middle of the two soil sections
~ Observe the worm's behavior
~ Once the worm's behavior has been observed, place a light over the tray
~ Turn it on and observe the worm's response to light
Observations
Wet or Dry Soil?:
~ Within the first few minutes of the experiment, the worm had made it's way toward the dry soil and then to the moist soil.
~ After another minute, the worm had it's full body on the wet soil and stretched out. It remained on the wet soil for the rest of the experiment.
Light Exposure:
~ The worm had been moving before the light was turned on, but when the lamp was turned on the worm ceased all movement for a few moments.
~ After a few more moments, the worm began to attempt to burrow into the wet soil; the soil was not deep enough to burrow into.
~ After five minutes, the worm became dehydrated and it's movement was little to none.
~ Within the first few minutes of the experiment, the worm had made it's way toward the dry soil and then to the moist soil.
~ After another minute, the worm had it's full body on the wet soil and stretched out. It remained on the wet soil for the rest of the experiment.
Light Exposure:
~ The worm had been moving before the light was turned on, but when the lamp was turned on the worm ceased all movement for a few moments.
~ After a few more moments, the worm began to attempt to burrow into the wet soil; the soil was not deep enough to burrow into.
~ After five minutes, the worm became dehydrated and it's movement was little to none.
Summary
The dependent variables of the is the worm's movement towards or away from the different soils (wet or dry) and the worm's movements towards and away from the light. The independent variables are the soil's saturation (100 mL of water) and the amount of light exposed to the worm. The data observed shows that the worm prefers wet/moist soil over the dry soil and that worms dislike direct exposure to light. Because worms breathe through their skin, wet soil is easier to breathe in. Worms can easily dehydrate and overheat because they're ectotherms. Possible sources of error could have been the use of estimated time rather than timing the experiment. Another source of error could be overstimulating the worm by touching it or adding more variables than what is being tested in the experiment which would affect the worm's behavior.