Name______________________________________________
Period_______________________________
Daphnia Experiment Writeup
In this experiment we will observe the population density and growth rate of Daphnia populations under two conditions.
Both bottles were set up the exact same way, but one change (independent variable) will be made in the experimental
bottle and the results in population will be measured over time.
The scientific question we are asking is:
Will doubling the amount of food in the Daphnia ecosystem, increase or decrease the population growth rate?
As we go through the setup, fill in each section.
1) Construction of the Control and Experimental Bottles:
a)
List the materials used to make the Daphnia bottles that were added exactly the same (constants).
b) What is the one thing that was added differently (the Independent Variable)?
2) Hypothesis
a) What is your hypothesis?
Hypothesis: Doubling the amount of food the Daphnia get will ______________________________
(increase/decrease) the population because_______________________________________________
___________________________________________________________________________________.
3) What are we going to measure (the dependent variable)?
a) The dependent variable is ______________________________________________________________.
4) Data Collection
Control Bottle (10-15 grains of yeast)
Date
Day
Number of
Daphnia
Population Density
(Number of Daphnia/Volume)
10/18
1
3
3 Daphnia /3.1 L = .97 Daphnia/L
Population Growth Rate
(Increase/Original Number x100 = r)
Experimental Bottle (20-30 grains of yeast)
Date
Day
Number of
Daphnia
Population Density
(Number of Daphnia/Volume)
10/18
1
3
3Daphnia / 3.1 L = .97 Daphnia/L
Population Growth Rate
(Increase/Original Number x100 = r)
5) Analysis – Graph your data and place the graph here.
6) Results and Discussions:
a) Outline the results of your study). Give all qualitative and quantitative observations. (What happened?)
b) Interpret your results and observations. Keep in mind the purpose of the experiment while interpreting
your results. (Why did it happen?)
7) Conclusions:
a) Explain the significance of your results and summarize your thoughts on them.
b) Discuss whether your hypothesis was proved or disproved.
c) Discuss what you would do next if you were to follow up this study.