Transcript BI143: Fundamentals of Life Science

BI143: Fundamentals of Life Science
THE PROCESS of SCIENCE
CHAPTER 1
SCIENCE:
The Body of Knowledge
Accumulated Using the
SCIENTIFIC METHOD
The Scientific Method
• Observations: Plants grow better in sunny
areas.
• Question: Do plants need sunlight to grow?
• Hypothesis: Plants need sunlight to grow.
• Prediction: If plants need sunlight to grow,
then plants not in sunlight will die.
The Scientific Method cont.
• Controlled Experiment:
– Control Group: Plants in sunlight
– Experimental Group: Plants without sunlight
– Independent Variable: Exposure to sunlight
– Dependent Variable: Growth of plants
• Data/Results: Plants with no sunlight die.
• Conclusion: Hypothesis is correct.
• Theory: ???
There is a difference between a theory
and a hypothesis
–A hypothesis is a proposed
explanation for a set of observations
–A theory is supported by a large and
usually growing body of evidence
The History of a THEORY:
SPONTANEOUS
GENERATION
ARISTOTLE’S THEORY
4th Century B.C.
REDI’S EXPERIMENT
• 1668
• Tries to disprove Spontaneous Generation of
small organisms (flies)
• Meat Sealed in jar: Produces no maggots
• Meat in Unsealed jar: Produces maggots
• Conclusion: Flies are needed to produce flies
• Problem with the experiment???
SPALLANZANI’S EXPERIMENT
• 1767
• Tries to disprove Spontaneous Generation of
Microorganisms
• Sterilizes broth by boiling it for 1 hour
• Broth in sealed flask produces no
microorganisms
• Broth in open flask produces microorganisms
• Problems with the experiment???
PASTEUR’S EXPERIMENT
• 1860
• Similar to Spallanzani’s experiment, but uses a
swan-neck flask instead of a sealed flask (let’s
“LIFE FORCE” from air into both flasks
• Flask with swan-neck produces no
microorganisms
• Material from the bend in the swan-neck flask
produces microorganisms
Mistakes Can Lead to Discovery
• Fleming discovers Penicillin (1929)
• Fleming was investigating the bacterium, staphylococci
• Fleming returned to his laboratory after a vacation and
noticed that one culture was contaminated with a
fungus
• The part of the culture near the fungus was killed
• Fleming identified the mold as being from the
Penicillium genus
• The substance (first antibiotic) that was produced by
the mold was named penicillin