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## The Effect of Light on Crayfish

 Researched by Bethany E. 1998-99

PURPOSE

The purpose of this experiment was to determine if Crayfish are attracted to light or repelled by light.

I became interested in this idea when I had Crayfish for a class pet in fourth grade, and didnít know weather to leave the lights on around them or to leave them in a dark area.

The information gained from this experiment it will help people who raise or sell Crayfish to then know how much light they should have shining on their Crayfish.

HYPOTHESIS

My hypothesis is that the majority of the Crayfish will move toward the darkness, and reject the bright light.

I base my hypothesis on books that I have read, on information that I have found on the Internet, and on observations that I have had in my classroom.

EXPERIMENT DESIGN

The constants in this study were:
The same amount of Crayfish in each aquarium
The same type of Crayfish
The same number of Crayfish
The same amount of water
The same amount of rocks
The same amount of Crayfish in each area depending on the trial
The same amount of time in between each trial.

The manipulated variable was light and no light.

The responding variable was the amount of Crayfish that responded to the light and the amount of Crayfish that responded to the darkness.

To measure the responding variable I will count the amount of Crayfish that are in each area, light and dark.

MATERIALS

 QUANTY ITEM DESCRIPTION 7 Northern Crayfish 1 Aquarium 12 cm. deep, 20.25long, and 10.5 cm. Wide 2 bags Rocks 2cm. Deep 3cm. deep Water 1 Foam divider 30.48 cm. high and 26.67 cm. Long

PROCEDURES

1. Collect materials
2. Take an (51cm.) aquarium and measure it into two parts, each being (10.125cm.).
3. Mark the dividing line on the top of the aquarium with a pen.
4. Get a foam divider that is30.48cm.high by 26.67cm.long, cut an opening in the foam divider 8cm wide and 6cm tall.
5. Divide the two aquarium halves with the foam divider.
6. Cover the bottom of each area with rock, 2cm deep.
7. Cover the bottom of each area with water 3cm.deep.
8. Cover the top of the left area with thick, black paper.
9. Cover the outside of both areas with thick, black paper.
10.Get a 60-watt light bulb and put it into a reading light.
11.Place the 60 watt reading light 75cm.above the bottom of the right side of the aquarium.
12.Turn the reading light on to the lowest setting.
13.Place all six of the crayfish into the right side.
14.Observe the crayfish for 30 min.
15.Record the number of crayfish in each area at 5min., 10min., 15min., 20min., 25min., and 30min.
16.Do setup 15 five different times.
17.Place all twelve crayfish in dark side.
18. Repeat steps 11,12, 14, and 15 five times.
19.Make a graph to see how many crayfish are on each side at each time.

RESULTS

The results were that the majority of the Crayfish ended in the Dark area, regardless of where they were placed in the beginning of the experiment.
My results indicate that my hypothesis should be excepted.  The majority of the Crayfish did go to the dark area.

CONCLUSION

My hypothesis was that the majority of the crayfish would be repelled by light, and choose to be in the dark area.
The results indicate that this hypothesis should be accepted, more Crayfish did choose to be in the dark area.
Because of the results of this experiment, I wonder if the light had of been closer if more of the crayfish would have gone to the dark area, or gone to the dark area faster.If I were to conduct this project again I would have more trials, I would move the light closer to the Crayfish, and I would run more practice trials.

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