The purpose of this
experiment was to see the survival rate of daphnia exposed to bleach.
I became interested in this idea because, I know how dangerous bleach is to our environment as well as us, if someone eats a polluted fish. We are in danger of poisoning the world, including ourselves. Water pollution is something I’ve been interested in for these reasons and many more.
The information gained from this experiment could help humans to see that we are in big danger if we don’t stop polluting the water, and hopefully would explain to them some of the items or “necessities” that we use in everyday life are extremely dangerous to our world.
HYPOTHESIS
My hypothesis was that the
bleach would kill the daphnia within twenty minutes, at almost any
concentration.
I based my hypothesis on the fact that bleach is considerably dangerous to humans. Daphnia, more than likely, are affected in a far worse way.
- The constants in this study were:
- The temperature of water
- The light each daphnia was put under
- The species of daphnia
- The experimental procedures
- The amount of daphnia in one dish
The manipulated variable was the concentration of bleach.
The responding variable was the survival rate of daphnia.
To measure the responding variable I observed the daphnia for gill movement. If the gills weren’t moving, I counted them as no longer living.
QUANTITY
|
ITEM
DESCRIPTION
|
16
|
Petrie Dishes
|
60
|
Daphnia
|
8 ML
|
Bleach
|
1192 ML
|
Water
|
1
|
Eye Dropper
|
7
|
200 ML Beakers
|
1
|
100 ML Graduated Cylinder
|
1
|
1 Liter Beaker
|
1. Get together the sixteen
petri dishes divided in to four quadrants,
a one
thousand ML beaker, a one hundred ML graduated cylinder, seven two hundred ML
beakers.
2. Make sure all these items are clean. If they aren’t clean follow the sub steps bellow.
A. Get a wet paper towel and clean off the bottom of the item.
B. If it still looks dirty after you clean off the bottom of the dish then just, rinse the item(s) several times under warm water.
C. After rinsing six to seven times, use a paper towel as a little scrubber. (You shouldn’t need soap)
D. Then dry the items with a dry paper towel.
3. Get out daphnia and put five in each quadrant using the eyedropper. (Put a drop of water in with each daphnia or they’ll die before the experiment is over!)
4. Fill the one Liter beaker with water, be sure that the water temperature at 20 degrees.
5. Pour 92 ML of water into a 200 ML beaker.
6. Add eight ML of bleach into the same beaker creating 8% of bleach. Label it ‘8%’.
7. Then, pour fifty ML of the mixture into the graduated cylinder.
8. Add fifty ML out of the one thousand ML beaker into the cylinder.
9. Pour the contents of the graduated cylinder into another beaker then back into the graduated cylinder and then back into the beaker again. (To mix it) Label this beaker 4%
10. Repeat steps 7-10 four times, but put the following labels on in the exact order: 2, 1, .5, .125.
11. Place the Petri dishes with the daphnia on the table in two rows of two.
12. With the first two daphnia dishes to the left, just put in three ML of water in each quadrant totaling at 24 ML of water.
13. Repeat step thirteen except use all of the mixtures in the beakers that you earlier made.
14.Check each Petri dish every ten minutes for 90 minutes.
15. Record the number of daphnia that are still alive in each dish.
RESULTS
The original purpose of
this experiment was to test the survival rate of daphnia against bleach.
The results of the experiment were that bleach killed daphnia quickly at low concentrations and at an even faster pace at high concentrations.
My
hypothesis was that the bleach would kill all of the daphnia, even at the
lowest concentration, within 20 minutes.
The
results indicate that this hypothesis should be accepted.
Because
of the results of this experiment, I wonder if daphnia are as vulnerable to
bleach if they’re in the wild.
If I
were to conduct this project again, I would be more organized about my whole
experiment, and check on the daphnia more often.
Researched
by --- Lauren G
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