The Scientific Method

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The Scientific Method

• How to perform a scientific experiment

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The Scientific Method

• Goal to be able to create an experiment that
  tests one variable with reproducible results

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The Mendel Experiment

• Gregor Mendel investigated the method of
  inheritance
• Did so using pea plants
• He did it not knowing anything about genetics or
  patterns of inheritancebut

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Genetic background

• Chromosomes have genes that code for specific
  proteins which have specific functions
• Each chromosome has an allele which is a genetic
  variation of that gene
• Ex- Flower colour gene could be purple or white
  depending on the combination of alleles

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Genetic background

• Each allele has a 50/50 chance of being passed to
  the next generation
• The offspring inherit 1 allele from each parent
• 1 allele may be dominant (P) and 1 may be
  recessive (p)
• What would the resulting offspring be if the
  parents were PP and pp?
• Pp all purple flowers

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Genetic background

• What would the the next generation be if the Pp
  offspring were crossed?
• 31 ratio Purple white flowers
• This experiment was the basis for what we know of
  genetics and inheritance

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Importance?

• The experimental procedures by Mendel produced
  accurate and repeatable results
• How? What did he do?

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Genetic background

• Sample Size was large
• Why did Mendel use large sample size? -Penny
  experiment
• Genetics are based on probabilities. The larger
  the sample size, the more likely the results will
  conform to probabilities.

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What else would impact the results?

• Trials- Doing the same experiment multiple times
• Eliminating every possible variable besides what
  is being tested

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Your experiment

• You are going to test the effect salinity has on
  the growth of kidney bean plants
• You will design your own experiment ensuring
  accuracy and repeatable results

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What do you need to do?

• Investigate the variable you are testing
• What is normal? Come up with your low and high
  salinity
• Come up with a hypothesis
• Set all of your controls
• Come up with a repeatable procedure
• Another scientist should be able to replicate
  your results using the procedure you describe

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Lab Template

• Introduction- Write up about what you plan to
  investigate
• Materials
• Procedure
• Results- Data tables, graphs, pictures
• Conclusion- restate results, adress hypothesis,
  explain results, sources of error

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Vocabulary to know before starting

• Control
• Independent variable
• Dependent variable
• Hypothesis
• Reliability
• Sample size
• Trial