1. How Do Scientists Conduct Controlled Experiments?

2. Microscope Care Use two hands to carry the microscope.
Do not place microscopes near the edge of the table.
The eyepiece magnifies 10x.
The low power magnifies 4x.
The total magnification under low power is 40x.

3. Writing a Testable Hypothesis
If ….. Then……
If earthworms are ectothermic (coldblooded) then when placed in cold water their heart rate will decrease.
If Miracle Grow is the best fertilizer then plants given Miracle Grow will grow the tallest.
If chocolate causes breakouts then teens that eat more chocolate will have more breakouts.
If I am organized then I will get better grades.

4. Independent vs. Dependent (responding) Variable
Independent Variable –
What did you add or change in the experiment?
Dependent (responding) Variable
What did you measure/count as a result of the change?

5. Daphnia magna
Daphnia molting
Water fleas are very small, usually 2-5 mm long, with an overall shape similar to a kidney bean. The body is enclosed by a transparent shell-like structure, called a carapace, that is mostly made of chitin. Due to its transparent carapace, this species tends to be the color of what it is currently eating. They have two sets of long, doubly branched antennae and six thoracic appendages that are held inside of the carapace and help to produce a current of water, carrying food and oxygen to their mouths and gills. They also have two large claws, used mainly for cleaning the carapace. They have one compound eye, which appears as an anterior dark spot, and one simple eye (ocellus). Males are smaller than females (typically only 2 mm long while females are 3-5 mm long) but have longer antennules and modified, hook-like first appendages used for clasping females during mating.

6. What Effect Does_____________ Have on Daphnia Heart Rate?
Stimulant – chemical that will increase heart rate.
Depressant – chemical that will decrease heart rate.
What effect do you think alcohol, nicotine and hydrogen peroxide will have on heart rate?

7. Observing Daphnia Heart Rate
experiment-video/tr11197.tr

8. Experimental Design Hypothesis- If/then testable statement
Procedure- written in detail for peer review
Experimental Setup- contains the variable being tested
Control Setup- used as a comparison. Does NOT contain the variable being tested.

9. Experimental Design
Constants - What factors should be kept the same in each setup?
Number of trials – more trials / samples taken increase reliability. Take average of all trials.
Data – What data will be collected? How will the data be presented? Data table &/or graph.
Conclusion - Do the results support or reject your hypothesis? Answer the question being investigated using your data.