The Nature of Science

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The Nature of Science

• What is Science?
• How do scientists work?

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Nature of Science
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Goal of Science

• To understand the world around us
• EX. Does life appear from non-living matter?
• To explain events by making predictions
• EX. Life doesnt appear from non-living matter.
• To investigate predictions
• EX. Setting up an experiment to see if life comes
  from non-living matter, or from living things

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How scientists work
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Observations- Gathering evidence

• It all starts here!
• Using SENSES to gather data
• Quantitative
• Observation using numbers and measurement
• Can you make a quantitative observation in this
  classroom?
• Qualitative
• Observation that doesnt involve numbers
• EX. Maggots are on raw meat
• Can you make a qualitative observation in this
  classroom?

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Inferences- Interpreting the Evidence

• INTERPRETATION based on observation and prior
  knowledge or experience
• EX. Maggots come from raw meat.
• Observation Maggots are on the meat
• Prior knowledge Maggots have always been found
  on raw meat
• Can you make an inference about something in the
  classroom?
• Observation
• Prior knowledge

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Hypothesis- Explaining the Evidence

• The answer to a BURNING QUESTION!
• Only useful if it can be tested!
• Evidence must be gathered and tested.
• Example
• Question Do living things come from non-living
  matter?
• Hypothesis Living things do not come from
  non-living things.
• We now must set up an investigation to test our
  hypothesis!!!!
• What is the process called that scientists use?
• SCIENTIFIC METHOD!

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The Scientific Method

1. State the problem (the burning question)
2. Form a hypothesis (answer to burning question)
3. Design a controlled experiment
4. Collect organized data
5. Analyze data
6. Form a conclusion (Was your hypothesis correct?)
7. Peer evaluation (Can your experiment be retested
   and always get same results?)

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Definitions

• Variable
• Things that can be manipulated or changed by
  scientist during experiment
• A controlled experiment tests ONE variable
• Independent (Manipulated variable)
• Manipulated by scientist
• Graphed on X-axis
• Dependent (Responding Variable)
• Responsive variable (tested against independent)
• Graphed on Y-axis
• Controlled Variables
• Things that must be kept constant during
  experiment
• If altered, can be used to show error in
  experiment

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Setting up a Controlled Exp.

• What does it mean to be a CONTROLLED experiment??

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1st Step Ask a Question
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Redis Experiment Scientific Method at work!

• Problem
• How do living things arise?
• Hypothesis
• Old view Living things arise spontaneously from
  non-living matter. (spontaneous generation)
• Maggots arise spontaneously on raw meat.
• New idea (proposed by Francesco Redi) Living
  things come from living things.
• Maggots come from flies that land on the meat.

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2nd Step Form a Hypothesis
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Redis Experiment Scientific Method at work!

• Design a controlled experiment to test hypothesis
• Redi used two jars, each with meat. One jar
  covered with gauze, one jar without gauze.
• Can you list the things that need to be kept
  constant (controlled variables)?
• Type of meat, type of jar, temperature, length of
  exposure
• Can you name the independent variable?
• gauze
• Can you name the dependent variable?
• maggots

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3rd Step Design and Conduct Exp.
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Redis Experiment Scientific Method at work!

• Collect data
• Written, drawings, etc
• Redis data
• Jar with no gauze maggots
• Jar with gauze no maggots
• Analyze data
• Redi figured that the gauze prevented flies from
  landing on the meat
• Draw a conclusion
• Redis hypothesis was correct. Living things do
  come from living things.
• Peer evaluation
• Redis experiment was tested and retested by
  others including Louis Pasteur

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Step 4 Analyze Results
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Step 5 Draw a Conclusion