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

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 The effecteffect of the variable being tested. 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 Try the worksheet on HGH. Try the worksheet on HGH.

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 on page Read about Redi’s first experiment on page 8 . In your notes, describe what Redi did in 8 . In your notes, describe what Redi did in each of the 6 steps of the Research Method. each of the 6 steps of the Research Method. ??

Observation (Ask a question) –Observation (Ask a question) – Hypothesis –Hypothesis – Controlled Experiment – Controlled Experiment – Data Collection (Qualitative/Quantitative)-Data Collection (Qualitative/Quantitative)- ConclusionConclusion Report ResultsReport Results

Controlled ExperimentControlled Experiment

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

(Why do maggots appear?)(Why do maggots appear?) 2. If flies land on decaying meat, then maggots will 2. If flies land on decaying meat, then maggots will

appear.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 ExperimentRedi's Experiment

Redi’s ExperimentRedi’s Experiment

AbiogenesisAbiogenesis Abiogenesis is a theory that says “living things can arise from Abiogenesis is a theory that says “living things can arise from

non-living things”non-living 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 described on p.11.Read about John Needham’s experiment described on p.11.

In your notes, describe his experiment. In your notes, describe his experiment. ??

From the next slide, answer the 2 questions. From the next slide, answer the 2 questions.

Needham’s ExperimentNeedham’s Experiment

What was his conclusionWhat was his conclusion ? ? What mistake(s) did he makeWhat 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 experiment, but made 2 changes in an attempt to disprove his conclusion. Check out his to disprove his conclusion. Check out his experiment on p. 11.experiment on p. 11.

What did he doWhat did he do ? ? Why were his findings not accepted Why were his findings not accepted ?? What would a scientist have to do to satisfy What would a scientist have to do to satisfy

the critics the critics ??

Louis PasteurLouis Pasteur

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

Read about his experiment on page 12 and describe what he Read about his experiment on page 12 and describe what he did in your notes. did in your notes. ??

Pasteur’s ExperimentPasteur’s Experiment

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 unanswered?Biogenesis leaves one important question 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

Answer the questions from the worksheet Answer the questions from the worksheet titled “How Scientist’s Work”. Use the page titled “How Scientist’s Work”. Use the page references from you textbook to find your references from you textbook to find your answers. answers.

I’ll be checking your results I’ll be checking your results