Emergence of the Cell Theory Objectives: 1. To understand the steps to the Research Method 2. Critique the experiments done to challenge Abiogenesis 3. Describe the “Cell Theory”

Research Method 1. Observation (Ask a question) 2. State a Hypothesis 3. Test the Hypothesis with a “controlled experiment” 4. Collect Data 5. Make a Conclusion 6. Report your Results

Assignment Observation/Question: Does HGH increase speed? Observation/Question: Does HGH increase speed? Hypothesis: If mice receive HGH, then they will run faster Hypothesis: If mice receive HGH, then they will run faster Variable: HGH Variable: HGH Variables kept constant: Types of mice; health of mice; food; environment; amount of HGH, etc Variables kept constant: Types of mice; health of mice; food; environment; amount of HGH, etc Quantitative Data: measurable data Quantitative Data: measurable data Qualitative Data: observable data (senses) Qualitative Data: observable data (senses) Conclusion: Mice receiving HGH run faster Conclusion: Mice receiving HGH run faster

Controlled Experiments Independent variable – (manipulated variable) Independent variable – (manipulated variable) The variable being tested. The variable being tested. Dependent variable – (responding variable) Dependent variable – (responding variable) The effect of the variable being tested. The effect of the variable being tested. Experimental Part – has the variable being tested Experimental Part – has the variable being tested Control part – lacks the variable being tested Control part – lacks the variable being tested Variables Variables Variables

Controlled Experiment

Let’s look at some experiments Francesco Redi conducted an experiment to prove that maggots could not mysteriously appear on decaying meat. Francesco Redi conducted an experiment to prove that maggots could not mysteriously appear on decaying meat. Read about Redi’s first experiment. In your notes, describe what Redi did in each of the 6 steps of the Research Method. Read about Redi’s first experiment. In your notes, describe what Redi did in each of the 6 steps of the Research Method.

Redi’s Experiment 1. Flies landed on the meat before maggots appeared. 1. Flies landed on the meat before maggots appeared. 2. If flies land on decaying meat, then maggots will appear. 2. If flies land on decaying meat, then maggots will appear. 3. Set up 2 jars, one covered and one open. 3. Set up 2 jars, one covered and one open. 4. Open jar had maggots and the closed one didn’t. 4. Open jar had maggots and the closed one didn’t. 5. Flies lay eggs that develop into maggots. 5. Flies lay eggs that develop into maggots. 6. Report his results. 6. Report his results.

Redi’s Experiment

Abiogenesis A theory that says “living things can arise from non-living things” A theory that says “living things can arise from non-living things” First proposed by Aristotle - maggots appearing on decaying meat/recipe for mice/worms found after rain First proposed by Aristotle - maggots appearing on decaying meat/recipe for mice/worms found after rain Anton vanLeeuwenhoek invented the first microscope. His discovery fuelled the debate about where life comes from. Anton vanLeeuwenhoek invented the first microscope. His discovery fuelled the debate about where life comes from. Read about John Needham’s experiment. Read about John Needham’s experiment.

Needham’s Experiment What was his conclusion? What was his conclusion? What mistake(s) did he make? What mistake(s) did he make?

Abiogenesis?? Lazzaro Spallanzani recreated Needham’s experiment, but made 2 changes in an attempt to disprove his conclusion. Check out his experiment. Lazzaro Spallanzani recreated Needham’s experiment, but made 2 changes in an attempt to disprove his conclusion. Check out his experiment. What did he do? What did he do? Why weren’t his findings accepted? Why weren’t his findings accepted? What would a scientist have to do to finally settle this controversy? What would a scientist have to do to finally settle this controversy?

Louis Pasteur Pasteur came up with a way to let air in, but keep microbes out. Pasteur came up with a way to let air in, but keep microbes out.

Pasteur’s Experiment

Pasteur was able to reduce the variables affecting his experiment down to one…..the microbes in the air! Pasteur was able to reduce the variables affecting his experiment down to one…..the microbes in the air! He disproved the Theory of Abiogenesis He disproved the Theory of Abiogenesis It was replaced with the Theory of Biogenesis It was replaced with the Theory of Biogenesis “Only life can produce life” “Only life can produce life” Biogenesis leaves one important question unanswered? Biogenesis leaves one important question unanswered? Where did the first living thing come from??? Where did the first living thing come from???

Cell Theory Robert Hooke looked at slices of cork under a microscope and saw little compartments he called Cells Robert Hooke looked at slices of cork under a microscope and saw little compartments he called Cells German scientists Schleiden and Schwaan discovered that plant and animal tissue was composed of cells. German scientists Schleiden and Schwaan discovered that plant and animal tissue was composed of cells. The Cell Theory The Cell Theory 1. The cell is the basic structural component of all life 2. The cell is the basic functional unit of all life 3. Only cells can produce cells