Download Biology As A Science

Biology As A Science
The Scientific Method:
Why have it?
Scientific Method
1. Define Problem
2. Formulate Hypothesis
3. Test Hypothesis
•
•
-Write out the materials and methods
needed
Need Positive and Negative Controls
What is a Control Group?
Beginning of Experiment
Positive Control
Group:
Experimental
Group:
Negative Control
Group:
Known fertilizer and
water
Experimental
fertilizer and water
Water only
150 ft
End of Experiment
90 ft
50 ft
What is a Variable?
What was the variable in the
example?
Independent vs. Dependent Variables
New Experiment
Positive Control
Group:
1 ounce known
fertilizer and
water
Experimental Group 1:
1 ounce experimental
fertilizer and water
Experimental
Group 2:
Negative
Control Group:
2 ounces of
water
experimental
fertilizer and water
150 ft
150 ft
130 ft
100 ft
How many variables were in the
experiment?
• Independent Variables:
– Number varies but you control it
– Ex. Amount of fertilizer you added
• Dependent Variables:
– Number varies but nature controls it
– Ex. Height reached by the tree
More Scientific Method
4. Collect Data:
– Display in form of graph or table or photo in a
“Results” section of a scientific paper
5. Analyze data and make conclusions
about data in a “Conclusions” section of a
scientific paper
How do we decide in an
objective way if measured
differences are significant?
• Ex. Avg Control Group Plant Height=12in
• Avg Experimental Group Plant Height= 12.7in
• 0.7 inches: Was this because of my fertilizer or just
by chance?
Statistics
Step 1: Null Hypothesis=premise that no
difference exists.
Step 2: Collect Data
Step 3: Use statistics to determine the
probability that any differences are due
to chance
Step 4: If there is a probability of error or
chance below 5% then Null Hypothesis
correct
More Scientific Method
6. Report your paper to
the world for
examination and
duplication
Theory vs. Law?
Theory
“Sick people
have Bacteria
A”
“Sick
People
have
Parasite
Q”
Germ Theory= Germs cause us to be sick
“Sick people
have Fungus
P”
“Sick people
have Virus
X”
• Theory= Established explanation given for
many different observations seen by
researchers
= Explanation for many proven
hypothesizes
Law
Law of Gravity=
•Things always fall towards the center of
Earth
•This event is always seen over and over
•Accepted at face value, no proof needed
•Law doesn’t go into How? and Why?
•Law based on 1000s of observations
The Metric System
• Length=Meter
• Volume=Liter
• Mass=Gram
Metric System
•
•
•
•
1 Meter= 1000000 micrometers or Microns
1 Meter= 1000 mm
1 Meter= 100 cm
1 Kilometer= 1000 meters
Question
• 2cm= ___ Microns?
• 50 micrometers= ____ mm?
Tools of a Biologist
• Light Microscopes:
– Simple Microscope (Single Lens-Magnifying Glass
(1600s)
– “Inventor”: really improved on existing technology
Microscopes
• Really 1590
invented by:
• Hans and
Zaccharias
Janssen (father
and son)
Tools of a Biologist
– Compound
Microscope (2 lenses)
– Robert Hooke (1600s)
Modern Compound Light Microscope
PARTS
Tissue Prep for Microscopy
2. Embed in wax
3. Slice with
Microtome, Mount on
slide, Stain
1. Fixation
Stains
• Help visualize details of specimen
– Vital Stains=Don’t harm living specimens (ex.
Methyl Blue)
– Lethal Stains=Kills Specimen (ex. Iodine)
Tissue Prep Center
Microtome
Water bath with
sliced
wax/tissue
Embedding Area
Tissue prep-Mount onto slides
Dissecting Scope/Zoom Scope
3D Image
More working space
Can view “large” objects
Cheek Cells using Phase-Contrast
Microscope
No Stains Needed
Can view live specimens
Scanning Electron Microscope
100,000X Magnification
Can’t view live organisms
3D Image
Blast electrons at object
Red Blood Cells using a
SEM
Transmission Electron Microscope
2D Image
Can’t View live
organisms
250,000X Mag
Blast electrons at object
Blood Cells using a TEM
Confocal Laser Microscope
Ever been in a centrifuge?
Centrifuge
• Separate mixtures based on density
• Most dense at bottom of tube
• Least dense at top
Chromatography
Separation into
components based
on solubility in
solvent
Sample
Solvent
Spectrophotometry
• Use light absorbance to determine the
concentration of substances
Detect amount of
light that made it
through
Spectrophotometry
Known
Absorbance #
Concentration
Unknown
Concentration
Absorbance #
Spectrophotometry
• Spectrophotometry Demo
Electrophoresis
Separate mixtures based
upon size and charge
Electrophoresis
Tissue Culture
Microdissection
Recombinant DNA
Transgenic Organisms
• Fluorescent
“Reporter” Genes