1. September 8, 2009
Objective: To review the steps of the scientific method
Do Now: (Fill in) When a hypothesis has been tested many times (and supported) it may become a __________. “If tried and true” it may become a scientific ________.
Do Now
Notes on How Scientists work
Answer 1 – 5 on p. 15

2. September 8, 2009
Objective: To review the steps of the scientific method
Do Now: (Fill in) When a hypothesis has been tested many times (and supported) it may become a __________. “If tried and true” it may become a scientific ________.
Do Now
SpongeBob Scientific Method Problems

3. The Scientific Method and Important Experiments in Biology
How Scientists Work
The Scientific Method and Important Experiments in Biology

4. Spontaneous Generation
Years ago scientists believed many living things appeared out of nowhere
Recipes for bees (Fig. 1-7)
Jean Baptist van Helmont in the mid-1600s. placed a moist cloth and wheat grain inside a closed, wooden box. To his astonishment, he found a mouse nibbling at the box within a few days.
Why do you think reasonable individuals once accepted these ideas?

5. Asking a Question
People wondered how events happened (such as mice appearing from grain)
They were identifying a problem!
The Question
How do new living things or organisms come into being?

6. Forming a Hypothesis
For centuries people accepted that things simply arose from non-living things
This idea or “educated guess” was given the name Spontaneous generation
Today we consider this a hypothesis
Many hypotheses were made and tested to disprove the original hypothesis of spontaneous generation

7. He tested this hypothesis by setting up a controlled experiment!
Francesco Redi formed the hypothesis that flies produced maggots based on his experiences.
He tested this hypothesis by setting up a controlled experiment!
Only one variable is changed at a time
The variable that is deliberately changed is called the independent or manipulated variable (“I Change”)
The variable that is observed to change due to manipulated variable is called the responding or dependent variable. (“What is Measured”)

8. Redi’s Experiment What was the Manipulated (Independent) Variable?
What was the Responding (Dependent) Variable?
Maggots Appear
NO Maggots Appear

9. Recording and Analyzing Results
Scientists usually keep records of their observations and data
In this class we will keep lab reports!!
This is done by describing and sometimes drawing pictures of observations
Today much of recording is done on computers
Today scientists publish their results in scientific journals such as the one pictured above.

10. Repeating Investigations
NOTHING IN SCIENCE IS FACT!
Results are tested, and tested, and tested…to ensure that they are REPEATABLE.
Scientists are expected to test each other; this ensures that the best science is being done
Communication is key to good science
A few scientists tested Redi’s findings…

11. Needham’s Test of Redi’s Findings
Hypothesized that Spontaneous Generation could occur under the right conditions

12. Spallanzani’s Test of Redi and Needham’s Results
Concluded that Needham’s test was flawed (he had not heated the broth enough) and improved upon his test
Hypothesis was supported that only new organisms are produced from existing organisms

13. Pasteur’s Test
Many scientists still argued that their were flaws in Spallanzani’s experiment (the animalcules were deprived of air).
Pasteur designed a new flask and tested spontaneous generation
He supported his hypothesis that all living things come from other living things.
His findings helped to convince others that spontaneous generation was not correct.

14. Impact of Pasteur’s Work
During his life Pasteur made many discoveries related to microorganisms
He saved the French wine industry and the silk industry
He began to uncover the nature of infectious diseases (they were the result of microorganism)
He is considered one of biology’s most remarkable problem solvers
*Refer to pages 12 and 13 of your text for other major discoveries in biology

15. When Experiments Are Not Possible
We cannot always do experiments to test a hypothesis
Ex. field studies of animal behavior (how can you study interactions in the wild in a laboratory?)
Ethical considerations
What can we do when experimentation is not possible?

16. How a Theory Develops
After much testing with supporting results a hypothesis may develop into a theory
Even spontaneous generation could have been considered a theory (there was a great deal of supporting evidence)
The hypothesis that new life comes from existing life is now considered the theory of biogenesis – meaning generating from life.

17. Theory
In science the word theory applies to a well tested explanation that unifies a broad range of observations.
They allow scientists to make accurate predictions about new situations
It is still important to note that NO theory is considered absolute truth and as new evidence becomes available theories may be modified or thrown out completely!

18. Questions
Answer the following questions in complete sentences (questions can be found on page 15 of text).
Why is Redi’s experiment on spontaneous generation considered a controlled experiment?
How does a scientific theory compare with a scientific hypothesis?
How do scientists today usually communicate their results and conclusions?
How did the design of Pasteur’s flask help him successfully refute the hypothesis of spontaneous generation?
Evaluate the impact of Pasteur’s investigations on scientists’ ideas and people’s lives.