1. Chapter 1 Section 3
The Methods of Science

2. Biologists use specific methods when conducting research.
Main Idea
Biologists use specific methods when conducting research.

3. What are the differences between an observation and an inference?
Thinking Questions
What are the differences between an observation and an inference?
What are the differences among a control, independent variable, and dependent variable?
What are the scientific methods that a biologist uses for research?
Why are the metric system and SI important?
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4. THE SCIENTIFIC METHOD Organized Problem Solving
Not a single, linear method

5. Steps to the Scientific Method
Define the Problem – Ask a Question/Make Observation
Form a Hypothesis
Design a Controlled Experiment
Collect Data
Analyze Data
Draw Conclusions
Communicate Results

6. 1. Ask a Question Begins with an observation
Direct method of gathering information in an orderly way
After making an observation, inferences are drawn
Combining what you know with what you have learned to draw a logical conclusion

7. 1. Ask a Question What are you trying to find out?
Based on observations
Stated as a question
Example: I notice on warm nights, the crickets seem to chirp more often
Problem: Does temperature affect the rate of cricket chirps?

8. 2. Form a Hypothesis Hypothesis Testable explanation of a situation
NOT SIMPLY AN EDUCATED GUESS!!
A possible solution to the problem; makes a prediction
Must be possible to be disproved
MUST BE MEASURABLE!!!!

9. 2. Form a Hypothesis Should be stated in “If…Then…because…” form
Relates to the experiment and explains the expected outcome
If I do this…Then that will happen, because…
Example: If I raise the temperature the crickets are kept in then they will chirp more, because they are cold-blooded.

10. Controlled Experiment Tests only one variable at a time
3. Design a Controlled Experiment
Controlled Experiment
Tests only one variable at a time
Compares a control group with an experimental group
Constant(s)
Factor(s) that remain the same across all groups in an experiment
Insures only one variable is tested

11. The group used for comparison Experimental Group
Control Group
The group used for comparison
Experimental Group
The group exposed to the factor being tested
Identical to the control group EXCEPT for what is being tested
3. Design a Controlled Experiment

12. Experimental Design Must be repeatable Should test a large sample
3. Design a Controlled Experiment
Experimental Design
Must be repeatable
Should test a large sample
Should be without bias

13. Variable = anything that can change in an experiment
3. Design a Controlled Experiment
Variables
Variable = anything that can change in an experiment
Controlled Variables = What do I keep the same? (same as constants)

14. Independent Variable = What do I change? (aka Manipulated Variable)
3. Design a Controlled Experiment
Variables
Independent Variable = What do I change? (aka Manipulated Variable)
Dependent Variable = What do I measure?

15. 4. Collect Data Cricket Experiment 20 crickets in 10 gallon container
Control Group
Experimental Group
20 crickets in 10 gallon container
12 hours light/day
Fed 5g cricket food
Kept at 60 degrees F
20 crickets in 10 gallon container
12 hours light/day
Fed 5g cricket food
Kept at 80 degrees F

16. Data = observations or measurements
5. Analyze Data
Data = observations or measurements
Quantitative = number data
10 chirps/minute
Qualitative = observations
Color Change
Results = processed data – makes the meaning of the data more clear (calculate an average, graph of data, etc.)

17. 5. Analyze Data
Graphing your Data
Independent variable – the factor that goes on the x-axis
Dependent Variable – the factor that goes on the y-axis

18. Sample Graph 5. Analyze Data Dependent Variable: on the Y Axis
Independent Variable on the X Axis

19. Was your hypothesis correct?
6. Draw Conclusions
Was your hypothesis correct?
Do the results support or refute your hypothesis?
What are the possible sources of error?
What next? What else could you study?
Why is this important?

20. Conclusions are reported in scientific journals
7. Communicate Results
Conclusions are reported in scientific journals
Conclusions go through peer review process
Procedures and results are evaluated by other scientists in a similar field conducting similar research

21. The Scientific Method!!!!

22. Let’s Practice!
MYTHBUSTERS!!

23. Let’s practice!
Smithers thinks that a special juice will increase the productivity of workers. He creates two groups of 50 workers each and assigns each group the same task (in this case, they're supposed to staple a set of papers). Group A is given the special juice to drink while they work. Group B is not given the special juice. After an hour, Smithers counts how many stacks of papers each group has made. Group A made 1,587 stacks, Group B made 2,113 stacks
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24. Let’s practice!
Bart believes that mice exposed to radiowaves will become extra strong (maybe he's been reading too much Radioactive Man). He decides to perform this experiment by placing 10 mice near a radio for 5 hours. He compared these 10 mice to another 10 mice that had not been exposed. His test consisted of a heavy block of wood that blocked the mouse food. He found that 8 out of 10 of the radiowaved mice were able to push the block away. 7 out of 10 of the other mice were able to do the same.
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25. Let’s practice!
Homer notices that his shower is covered in a strange green slime. His friend Barney tells him that coconut juice will get rid of the green slime. Homer decides to check this this out by spraying half of the shower with coconut juice. He sprays the other half of the shower with water. After 3 days of "treatment" there is no change in the appearance of the green slime on either side of the shower.
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26. A student investigated whether ants dig more tunnels in the light or in the dark. She thought that ants used the filtered light that penetrated the upper layers of earth and would dig more tunnels during the daytime. Ten ant colonies were set up in commercial ant farms with the same number and type of ants per ant farm. The same amount of food was given to each colony, and the colonies were in the same temperature. Five of the colonies were exposed to normal room light and five were covered with black construction paper so they did not receive light. Every other day for three weeks the length of the tunnels was measured in millimeter using a string and a ruler. Averages for the light and dark groups for each measured were then computed. The averages are listed in the following chart.