The scientific method: Asking a question Doing background research Constructing a hypothesis

1. The scientific method: • Asking a question • Doing background research • Constructing a hypothesis • Testing the hypothesis with an controlled experiment • Analyzing the data & drawing a conclusion - Was the hypothesis correct? • Sharing results Transpiration experiment

2. Many years ago, people wanted to know how living things came into existence. ?

3. They observed that maggots (fly larvae) appeared “suddenly” on uncovered meat, and that frogs came from puddles. Maggots appeared on uncovered meat. Frogs appeared in puddles. Why might people have believed that these animals arose from nonliving material? No microscopes yet.

4. They though baby turtles were created from wet sand. They really did.

5. Spontaneous generation is the belief that life can come from nonliving things. Spontaneous = sudden Generation = creation (genesis) Aristotle believed in spontaneous generation! According to this theory, maggots “come from” meat.

6. Redi had different hypothesis: that flies produced the maggots. He disproved spontaneous generation. How Redi disproved spontaneous generation

7. Redi tested his hypothesis using a controlled experiment. • In a controlled experiment, only ONE variable is changed. All other variables are controlled (kept the same). Which variable in Redi’s experiment was changed? Which variables in Redi’s experiment were controlled? Gauze covering Size/type of jar, size/type of meat, location of jar, temperature

8. The variable that is changed is called the manipulated variable. How many manipulated variables are in a controlled experiment? What was the manipulated variable in Redi’s experiment? One Gauze covering

9. The variable that is measured is called the responding variable. What was the responding variable in Redi’s experiment? The maggots

10. In a controlled experiment, only one variable is changed to ensure that the response was caused by that change. • Would Redi have gotten the same results if he had also put different types of meat in each jar?

11. Redi recorded data by counting the number of maggots that appeared in each jar. What was Redi’s hypothesis? Based on the data he collected, was Redi’s hypothesis correct? That maggots came from flies that landed on the meat. Yes!

12. Graph Showing Redi’s Results 1. Labels Number of Maggots Time (Days) Time should be shown on the X-axis

13. Graph Showing Redi’s Results 1. Labels Number of Maggots Time (Days) Time should be shown on the X-axis

14. Graph Showing Redi’s Results 2. Data Range Number of Maggots Time (Days) Data Range: Lowest and Highest Values

15. Graph Showing Redi’s Results 3. Key Number of Maggots Time (Days)

16. Redi’s experiment was significant because it provided evidence against spontaneous generation. Despite his solid experimental data, Redi was continually attacked by other scientists who were supporters of S.G.

17. As scientific tools (such as microscopes) improved, the S.G. hypothesis was finally discarded. The controlled experiment – used by Redi 300 years ago – is now the standard way to conduct a scientific investigation.