Chapter 1 Section 3 The Methods of Science

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

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? Copyright © McGraw-Hill Education

THE SCIENTIFIC METHOD Organized Problem Solving Not a single, linear method

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

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

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?

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!!!!

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.

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

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

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

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)

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?

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

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.)

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

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

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?

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

The Scientific Method!!!!

Let’s Practice! MYTHBUSTERS!!

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 Copyright © McGraw-Hill Education

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. Copyright © McGraw-Hill Education

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. Copyright © McGraw-Hill Education

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.