Emergence of the Cell Emergence of the Cell TheoryTheory

Objectives: Objectives: 1.1. To understand the steps to the To understand the steps to the

Research MethodResearch Method2.2. Critique the experiments done to Critique the experiments done to

challenge Abiogenesischallenge Abiogenesis3.3. Describe the “Cell Theory” Describe the “Cell Theory”

Research MethodResearch Method

1.1. Observation (Ask a question)Observation (Ask a question)2.2. State a State a HypothesisHypothesis3.3. Test the Hypothesis with a “Test the Hypothesis with a “controlled controlled

experimentexperiment””4.4. Collect Collect DataData5.5. Make a Make a ConclusionConclusion6.6. Report your Report your ResultsResults

AssignmentAssignment

Observation/Question:Observation/Question: Does HGH increase speed? Does HGH increase speed? Hypothesis: Hypothesis: If mice receive HGH, then they will run If mice receive HGH, then they will run

fasterfaster VariableVariable: HGH: HGH Variables kept constant: Variables kept constant: Types of mice; health of Types of mice; health of

mice; food; environment; amount of HGH, etcmice; food; environment; amount of HGH, etc Quantitative DataQuantitative Data: measurable data: measurable data Qualitative DataQualitative Data: observable data (senses): observable data (senses) ConclusionConclusion: Mice receiving HGH run faster: Mice receiving HGH run faster

Controlled ExperimentsControlled 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 testedExperimental Part – has the variable being tested Control part – lacks the variable being testedControl part – lacks the variable being tested VariablesVariables

Controlled ExperimentControlled Experiment

Let’s look at some experimentsLet’s look at some experiments Francesco Redi conducted an experiment to Francesco Redi conducted an experiment to

prove that maggots could not mysteriously prove that maggots could not mysteriously appear on decaying meat.appear on decaying meat.

Read about Redi’s first experiment . In your Read about Redi’s first experiment . In your notes, describe what Redi did in each of the 6 notes, describe what Redi did in each of the 6 steps of the Research Method.steps of the Research Method.

Redi’s ExperimentRedi’s Experiment 1. Flies landed on the meat before maggots 1. Flies landed on the meat before maggots

appeared.appeared. 2. If flies land on decaying meat, then maggots 2. If flies land on decaying meat, then maggots

will appear.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 4. Open jar had maggots and the closed one

didn’t.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 ExperimentRedi’s Experiment

AbiogenesisAbiogenesis A theory that says “living things can arise from non-living A theory that says “living things can arise from non-living

things”things” First proposed by Aristotle - maggots appearing on decaying First proposed by Aristotle - maggots appearing on decaying

meat/recipe for mice/worms found after rainmeat/recipe for mice/worms found after rain

Anton vanLeeuwenhoek invented the first microscope. His Anton vanLeeuwenhoek invented the first microscope. His discovery fuelled the debate about where life comes from. discovery fuelled the debate about where life comes from.

Read about John Needham’s experiment.Read about John Needham’s experiment.

Needham’s ExperimentNeedham’s Experiment

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

Abiogenesis??Abiogenesis?? Lazzaro Spallanzani recreated Needham’s Lazzaro Spallanzani recreated Needham’s

experiment, but made 2 changes in an attempt to experiment, but made 2 changes in an attempt to disprove his conclusion. Check out his experiment.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 What would a scientist have to do to finally settle this

controversy?controversy?

Louis PasteurLouis Pasteur

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

Pasteur’s ExperimentPasteur’s Experiment

Pasteur’s ExperimentPasteur’s Experiment

Pasteur’s ExperimentPasteur’s Experiment

Pasteur’s ExperimentPasteur’s Experiment Pasteur was able to reduce the variables affecting his Pasteur was able to reduce the variables affecting his

experiment down to one…..the microbes in the air!experiment down to one…..the microbes in the air!

He disproved the Theory of AbiogenesisHe disproved the Theory of Abiogenesis

It was replaced with the It was replaced with the Theory of BiogenesisTheory of Biogenesis ““Only life can produce life”Only life can produce life” Biogenesis leaves one important question Biogenesis leaves one important question

unanswered?unanswered? Where did the first living thing come from???Where did the first living thing come from???

Cell TheoryCell Theory Robert Hooke looked at slices of cork under a Robert Hooke looked at slices of cork under a

microscope and saw little compartments he called microscope and saw little compartments he called CellsCells

German scientists Schleiden and Schwaan German scientists Schleiden and Schwaan discovered that plant and animal tissue was discovered that plant and animal tissue was composed of cells.composed of cells.

The Cell TheoryThe Cell Theory1.1. The cell is the basic structural component of all lifeThe cell is the basic structural component of all life2.2. The cell is the basic functional unit of all lifeThe cell is the basic functional unit of all life3.3. Only cells can produce cellsOnly cells can produce cells