1. How Scientists Work How Scientists Work Chapter 1-2

2. The Scientific Method Methodical and deliberate set of steps scientists use to try and identify relationships between two events

3. Steps of the Scientific Method Observation Hypothesis Experiment Data / Results Conclusion Report

4. Experiment Process of testing the hypothesis Controlled experiment -Tests 1 factor at a time and uses a control group -Control group – serves as a standard of comparison because the group receives no experimental treatment

5. Experimental Group –Group in which the manipulated variable is changed Dependent vs. Independent variables Variable: the 1 factor that is changed w/in the experimental group Manipulated variable (independent variable) Variable being tested or changed Responding variable (dependent variable) Any variable that is altered as a result of the change of the manipulated variable

6. Limitations of Science Controlled environments may not cause the same results as natural environments would –Ex: Animals in their natural habitat vs. a lab or a zoo Ethical dilemmas –Studies on animals or humans Ex: Stem cell research

7. Theories In science, the word theory applies to a well- tested explanation that unifies a broad range of observations –It is a hypothesis that is very well supported by experimentation and data Biogenesis Can be revised over time if new information is found

8. The Application of The Scientific Method: The Theory of Biogenesis (Disproving Spontaneous Generation)

9. The Beginning Early “scientists” believed that living things followed a set of natural rules that were different from those for nonliving things Also thought that special “vital” sources brought some living things into being from nonliving things –Spontaneous generation

10. Francesco Redi 1668 Challenged the idea of spontaneous generation –Proposed the hypothesis that flies produce maggots

11. Redi’s Experiment

12. John Needham Mid 1700’s Set up experiments to attack Redi’s work –Found “animalcules” under the microscope Spontaneous generation was believed in again

13. Lazzaro Spallanzani Wanted to improve upon Needham’s work –Didn’t think he heated the broth long enough Ended up supporting Redi’s work –Spontaneous generation was proven wrong again

14. Louis Pasteur 1864 Ended the debate on spontaneous generation with his experiments