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The Affect of Light on the Behavior of Daphnia

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Bailey m

on 8 March 2013

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Transcript of The Affect of Light on the Behavior of Daphnia

The Affect of Light on the Behavior of Daphnia.
-Bailey McIntosh Introduction Data Daphnia are freshwater organisms that are extremely abundant in permanent water sources. They have a light-sensing organ that allows them to tell the difference between a lighted or dark environment.“It is clear that changes in light intensity have a strong effect on initiating changes in behavior” (Ringelberg, 1987).
It has been studied whether certain levels of light affect how fast or slow a daphnia moves through water. In my experiment, I wanted to test whether daphnia preferred light or dark.

The independent variable is light and no light, and the dependent is the amount of time that the daphnia stayed in each section. Hypothesis If a daphnia is placed in an environment with
one side light and another side dark,
then it will spend an equal amount of time
on both sides Materials 1 daphnia
1 dropper
1 50 mL beaker
Two water bottles
Stop watch
Black construction paper
Flashlight Method 1.cut off the ends of two water bottles
2. put the cut ends of the two water bottles from step 1 and taped them together
3. take the cap off one end and fill up the bottles with water
4.fill beaker with water(enough for the daphnia)
5.use the dropper to retrieve one daphnia and drop it in the beaker
6.pour the daphnia into the water bottles through the top
7.cover one end of the water bottle in black construction paper
8.turn the flashlight on and put it over the side that does not have the construction paper
9.for 10 minutes, time how long the daphnia spends in the light
10.after 10 minutes, retrieve the daphnia and put it back in its beaker
11.clean up experiment 7.86
45.15 Time spent in light Total time spent in light: 379.16 sec
Total time spent in dark: 220.84 sec Expected: 300 sec | 300.00 sec
Observed: 379.16 sec | 220.84 sec

(379.16-300)2 / 300 + (220.84-300)2 /300 =
degrees of freedom: 1
Table value with 1 degree of freedom is 3.84, therefore i reject the null hypothesis. Though the daphnia would swim back and forth between the light and dark areas, the daphnia seemed, however to prefer the light.
The chart shows all the times the daphnia was in the light and for how long. The total time of seconds spent in the light is 379.16. Since there are 600 seconds in 10 minutes, 600- 379.16 gives the time that the daphnia was in the dark. The graph comparitively shows the differences in times. conclusion: In this experiment it was found that daphnia do prefer light over darkness, which refects my initial hypothesis that daphnia will not have a preference. The daphnia spent 379.61 seconds in light, versus 220.84. It was determined that these results were significant, and the null hypothesis was consequently rejected.
Now knowing that daphnia prefer light, we can start asking bigger questions. Why? With this knowlege as a base, it can be used to test other things, like coinciding with food preferences and habitat/evironment. understanding smaller speicies like water fleas helps us in turn learn about the rest of the world. In doing this experiment again, i would use more daphnia. A larger test group make for more accurate data. Also, i would want to time how long the daphnia was in the dark as well. Works Cited
Dodson, Stanley I., et al. "Individual swimming behavior of Daphnia: effects of food, light and container size in four clones." Journal of Plankton Research 19.10 (1997): 1537-52. Web. 8 Mar. 2013. <http://plankt.oxfordjournals.org/content/19/10/1537.full.pdf>.

Miller, C. 2000. "Daphnia pulex" (On-line), Animal Diversity Web. Web. 8 Mar. 2013. http://animaldiversity.ummz.umich.edu/accounts/Daphnia_pulex/
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