What is the goal of science? P. 3 Investigate and understand the natural world. Explain the natural world. Predict events in the natural world.

Science is a way of knowing. What does that mean?

Biology is the study of living things. Bio: Living Abio: Non-living

Thinking like a scientist P. 4

Thinking like a scientist Observation Data Quantitative Qualitative Use data to make inferences

Scientific Method Page 8 Asking a question Research Forming a hypothesis Setting up a controlled environment in which only one variable is changed at a time Recording and analyzing the results Drawing a conclusion Repeating the investigation

The hypothesis of spontaneous generation For centuries, people believed that life came from nonliving matter. Aristotle was a big believer in spontaneous generation (also called abiogenesis) which states that: living things come from non-living things ie. Flies came from a dead cow Frogs come from mud Mice come from dirty rags

Fransesco Redi page 11 In 1668, Fransesco Redi, an Italian physician attempted to disprove the theory of spontaneous generation. Based on his observations of maggots on meat, he developed a different hypothesis – flies produce maggots, which in turn produce flies.

Controlled Experiment Whenever possible, a hypothesis should be tested by an experiment in which only one variable is changed at a time. All other variables should be kept unchanged or controlled. The variable that is deliberately changed is called the manipulated variable (or independent variable).

Look at Redi’s experiment and figure out what his hypothesis was and which was the manipulated variable.

Redi’s Experiment

John Needham Mid 1700s British Needham tried to prove that spontaneous generation could occur in the right circumstances. (He disagreed with Redi.)

John Needham’s Experiment

Needham boiled broth, claiming to have killed all of he “animalcules” in it. After a few days, he used a newly developed microscope to have a look and saw many of the little animals. What was wrong with his experiment? How may this have affected his results?

Lazzaro Spallanzani Italian Felt that Redi was right and that Needham’s experiment had failed because he did not boil the broth long enough or did not have a tight enough stopper. He boiled 2 containers of gravy, sealed one by melting the glass at the top and left the other open.

Spallanzani After a few days: - the open container was teeming with microorganisms and was cloudy. - the sealed container remained free of organisms. Conclusion: The broth did not produce living things. The microorganisms in the open container were the offspring of microorganisms that had entered through the air.

Louis Pasteur 1864 French Designed a flask that would disprove spontaneous generation once and for all and conducted a controlled experiment using it.

Pasteur

“Theory” Page 13 In science, a theory is a well-tested explanation that unifies a broad range of observations. What’s the difference between a theory and a hypothesis?