Download - Unit 1—Ch 2
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Unit 1—Ch 2Biology as a Science
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•Microscopes were 1st introduced in the 1600’s by Galileo. Shown here is Robert Hooke’s simple microscope.
http://www.moonmentum.com/blog/wp-content/uploads/2010/03/Robert-Hooke.jpg http://micro.magnet.fsu.edu/primer/anatomy/introduction.html
Microscopy timeline
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Microscopes• use to magnify & to increase resolving power• common lab microscopes uses light passing through
an object & lens to produce a larger image– Simple light microscope– Compound light microscope
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Compound Light Microscopes• Uses light & 2 or more
glass lenses to focus light– Total magnification
• Eyepiece• Objectives• Total magnification up to
2000x
• Lower resolving power• live & dead specimens• COLOR!!!• Many are portable
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Light Microscopes• Shown here are an amoeba (left), stoma
in leaf (center) & onion cells (right).
stoma
Stains help us to see some specimens better…
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Parts of a compound light
microscope
Microscope parts quiz
Interactivemicroscopeguide
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Microscope parts
http://www.science.smith.edu/departments/Biology/Bio111/Labmanual/scope.jpg
Virtual Microscope
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Making a Wet Mount Slide
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Electron Microscopes• developed in 1960’s
• beam of electrons & magnetic lenses produce enlarged image
• only dead specimens
• greater resolving power & magnification than light microscope– 10,000-200,000x
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Transmission Electron Microscope (TEM)• Electrons pass through very thin non-living specimen
– Black & white, 2-D, image of inside
– Specimen frozen or embedded in plastic first
• resolution: 0.5 - 10 nm• magnification: > 1,000,000x
http://nobelprize.org/educational/physics/microscopes/tem/index.html
TEM simulator
Preparation of a specimen
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Scanning Electron Microscope (SEM)• electrons bounce off
surface of non-living specimen– Black & white, 3-D, image
of surface• Micrographs can be color
enhanced using computer
• Magnification < TEM– 100,000x plus
• Resolving power < TEM
SEM Interactive
Virtual SEM
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SEM Micrographs
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The samples shown above are (clockwise from top left) an ant (Lasius flavus), passion fruit (Passiflora caerulea) pollen, a freshwater shrimp parasite (Epistillis sp.), sunflower
(Helianthus anuus) pollen and central, agreenbottle (Lucilia sericata) foot.
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Comparison of Microscopes
Characteristic Compound Microscope
Transmission E. Microscope
Scanning E. Microscope
Resolution (Average) 500 nm 10 nm 2 nm
Resolution (Special) 100 nm 0.5 nm 0.2 nm
Magnifying Power up to 1,500X up to 5,000,000X ~ 100,000X
Depth of Field poor moderate high
Type of Objects living or non-living non-living non-living
http://universe-review.ca/R11-13-microscopes.htm
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Science & Technology• Science- is an organized process that produces a
body of knowledge about nature.– Based on observation of phenomenon or their effects &
experimentation in order to attempt to explain the cause of those effects
– Goal is to produce useful models of reality
• Technology- Applying knowledge to real problems
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The Scientific Method
http://www.sciencebuddies.org/science-fair-projects/overview_scientific_method2.gif
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The Scientific Method• Observations• question or problem to investigate• background information• hypothesis is formed
– “If _(IV)_, then _(DV)_, because __.”
• Test hypothesis controlled experiment
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• Controlled experiment–to be valid has to have these two parts!!!!!
• 1. Tests one variable, all others kept same– Independent Variable (IV)–Dependent Variable (DV)–Controlled Variables
or Constants (Cv)
–2. Two groups must be tested.–control group (set-up)–experimental group (set-up)
• Multiple Trials (replicates)– Ensure results are accurate
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• Make observations & collect data– data tables
• Interpret data & analyze results– graphs
• Draw conclusions– Support/reject hypothesis (NOT prove/disprove)
• Conduct additional experiments (revise or discard hypothesis if rejected)
• Communicate results– Report & publish
The Scientific Method
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Which brand of mouthwash gets rid of stinky breath the best?
• Independent Variable-
• Dependent Variable-
• Controlled Variables-
• Experimental Group(s)-
• Control Group-
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Theories & Laws• Can you prove anything in science?
• Theory– hypothesis becomes theory when it has been
supported repeatedly by experimental evidence• ex. evolution, natural selection, relativity
– used to explain laws– as close to complete explanation as science can offer
• can change/be refuted based on new evidence.
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Examples of Theories• Darwin’s finches
ex. of his theory of evolution through natural selection
• Lack of proper experimentation led to belief in abiogenesis (spontaneous generation)– Controlled experiments like
F. Redi’s “maggots from meat” experiment refuted this theory.
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• Laws• Statements about events that always occur
in nature• Does not give mechanism or explanation of
phenomenon• often expressed as a numerical equation
Theories & Laws
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Examples of Laws
• Newton
• Nicolas Steno’s Law of Superposition• Fossils in lowest layer
are oldest, in uppermost layer are youngest