unit 1—ch 2
DESCRIPTION
Unit 1—Ch 2. Biology as a Science. Microscopes were 1 st introduced in the 1600’s by Galileo. Shown here is Robert Hooke’s simple microscope. Microscopy timeline. http://micro.magnet.fsu.edu/primer/anatomy/introduction.html. - PowerPoint PPT PresentationTRANSCRIPT
Unit 1—Ch 2Biology as a Science
•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
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
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
Light Microscopes• Shown here are an amoeba (left), stoma
in leaf (center) & onion cells (right).
stoma
Stains help us to see some specimens better…
Parts of a compound light
microscope
Microscope parts quiz
Interactivemicroscopeguide
Microscope parts
http://www.science.smith.edu/departments/Biology/Bio111/Labmanual/scope.jpg
Virtual Microscope
Making a Wet Mount Slide
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
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
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
SEM Micrographs
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.
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
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
The Scientific Method
http://www.sciencebuddies.org/science-fair-projects/overview_scientific_method2.gif
The Scientific Method• Observations• question or problem to investigate• background information• hypothesis is formed
– “If _(IV)_, then _(DV)_, because __.”
• Test hypothesis controlled experiment
• 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
• 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
Which brand of mouthwash gets rid of stinky breath the best?
• Independent Variable-
• Dependent Variable-
• Controlled Variables-
• Experimental Group(s)-
• Control Group-
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.
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.
• 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
Examples of Laws
• Newton
• Nicolas Steno’s Law of Superposition• Fossils in lowest layer
are oldest, in uppermost layer are youngest