Emergence of the Cell Theory Objectives: 1. Critique the experiments done to challenge Abiogenesis 2. Describe the “Cell Theory”

Abiogenesis Theory states that non-living things can be spontaneously changed into living things. Theory states that non-living things can be spontaneously changed into living things. Also referred to as the theory of spontaneous generation. Also referred to as the theory of spontaneous generation. Developed by Aristotle the ancient Greek philosopher. Developed by Aristotle the ancient Greek philosopher.

Francesco Redi An Italian doctor tried to disprove this theory of abiogenesis. An Italian doctor tried to disprove this theory of abiogenesis. Left 4 jars of rotting meat open to the air, after a while found maggots on the meat and flies hovering in the air. Left 4 jars of rotting meat open to the air, after a while found maggots on the meat and flies hovering in the air.

Redi repeated the same thing again but covered 2 of the jars with a lid. Result, No maggots on the meat that was covered. Concluded that flies came from flies not rotting meat, disproving Aristotle’s theory of Abiogenesis. Right? Redi repeated the same thing again but covered 2 of the jars with a lid. Result, No maggots on the meat that was covered. Concluded that flies came from flies not rotting meat, disproving Aristotle’s theory of Abiogenesis. Right?

Hold On ! The supporters of Abiogenesis said the covered jars were different from the controlled jars, no fresh air circulated around the meat. They claimed that the air was the “Active Ingredient” that caused spontaneous generation” The supporters of Abiogenesis said the covered jars were different from the controlled jars, no fresh air circulated around the meat. They claimed that the air was the “Active Ingredient” that caused spontaneous generation”

Redi’s Final Try He put a fine mesh wire over the jars so air could circulate, result NO maggots. Proved rotting meat can’t be changed into flies. He put a fine mesh wire over the jars so air could circulate, result NO maggots. Proved rotting meat can’t be changed into flies. However, critics said that the mesh was too fine to let this “Active Ingredient” into the jars. So abiogenesis was NOT yet disproved! However, critics said that the mesh was too fine to let this “Active Ingredient” into the jars. So abiogenesis was NOT yet disproved!

Analyze Redi’s Experiment Using The Scientific Method 1. Ask a Question? 2. State the Hypothesis. 3. Set up Controlled Experiment: A. Which container is the control group? B. Which container is the experimental group? C. What is the independent variable? D. What is the dependent variable? 4. Analyze Data: What kind of data did Redi collect? 5. State a conclusion. 6. Report Results (omit)

John Needham The meat broth was teaming with microbes that made it look cloudy. The meat broth was teaming with microbes that made it look cloudy. He heated it for a short time until the meat broth was clear. He heated it for a short time until the meat broth was clear.

After a few days, microbes were present. He concluded that microbes came from non-living things thus supporting Abiogenesis. After a few days, microbes were present. He concluded that microbes came from non-living things thus supporting Abiogenesis. Two big problems, he used a cork seal to allow air to circulate but it allowed microbes to enter. Secondly, he heated the broth for a short time and didn’t destroy all the microbes. POOR SCIENCE ! Two big problems, he used a cork seal to allow air to circulate but it allowed microbes to enter. Secondly, he heated the broth for a short time and didn’t destroy all the microbes. POOR SCIENCE !

Lazzaro Spallanzani He performed Needham’s experiment but melted the glass at the top of the flask to seal it and then heated it for a long time. He performed Needham’s experiment but melted the glass at the top of the flask to seal it and then heated it for a long time.

The result showed no microbes present. The result showed no microbes present. However, critics claimed once again that the “Active Ingredient” in the air was not allowed to enter the flask. So Abiogenesis was not yet disproved! However, critics claimed once again that the “Active Ingredient” in the air was not allowed to enter the flask. So Abiogenesis was not yet disproved!

Louis Pasteur to the rescue !

Louis Pasteur Pasteur heated an open flask containing microbe filled meat broth for a long time killing all the microbes. Pasteur heated an open flask containing microbe filled meat broth for a long time killing all the microbes.

He then let it sit for a few days and it was teaming with microbes. He then let it sit for a few days and it was teaming with microbes. He hypothesized that the microbes must have entered from the air. He hypothesized that the microbes must have entered from the air.

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