The Nature of Science
2-1 The Scientific Method
Tries to find general principles to explain why things are as they are and why things happen the way they do.
Specialists: physicists, chemists, astronomers, earth scientists, biologists
Universal approach
Defining the Problem
Question - usually followed by a thorough search for information
data from reports from scientific journals
existing knowledge
no duplication
Formulating a Hypothesis
Define: a possible explanation for an observed set of facts.
Critical step
Testing the Hypothesis - Experimentation
To test a hypothesis - carry out same experiments that established the pattern or relationships
Good hypothesis will predict other types of patterns that have not been observed.
Design will prove or disprove the hypothesis
Repeated effects from experiment
controlled experiment - two identical setups
variable - isolate and test a single factor
control - set up has no change and serves as a reference
Observing and Measuring
Must include observations
Generalizations are not very useful
Accurate measurements and statement of results in numeral or quantitative form
Special tools and instruments
Analyzing and Drawing Conclusions
Data need to be analyzed
Interpret results and draw conclusions
Data can provide evidence to support, modify, or reject a hypothesis or to formulate a new hypothesis
Reporting Observations
No secrecy
Reported in detail
Experiment must be repeated by other investigators for results to be valid
Publish a paper
Scientific Journals
Reviewed by other scientists
Correct scientific methodology
Results reported clearly
Conclusions supported by experimental data
Criticisms and suggestions passed on to original scientist
Theories and Laws
Theories- explanations that apply to a broad range of phenomena and that are supported by experimental evidence.
Germ theory, Louis Pasteur
Scientific Law- is a statement that describes some aspect of a phenomenon that is always true. A law does not explain how or why something occurs as it does
scientists can state a law only after they have observed the particular events
Scientific Measurement
SI - International System of Units
Metric system
meters, grams, liter,second, Celsius or Kelvin
Biologists use small units - micrometers
micron -
m , one-millionth of a meter 0.001 mm
2-1 Section Reviews answers
2-2 Tools of the Biologist
Observations and measurements are the backbone of scientific investigation.
The Light Microscope
Any device that uses light to produce enlarged view of an object
image - object
magnification - ratio of image size to object size
lenses - curved glass, bends light
The Simple Microscope
Magnifying glass
single lens
10 th century
still used today
used to make quick observations in the field
The Compound Microscope
Uses two lenses
Optical system
objective, ocular, low-power objective, high-power objective
Mechanical system
base, arm, stage, two clips, body tube, nosepiece, coarse adjustment, fine adjustment
Magnification
Enlargement of an image
Magnifying power
100 x
Total magnification
multiply power of objective by the magnification power of the ocular
Resolution
Shows two points that are close together as separate images
Sharpness of a image
Depends on precision and quality of the lens
Preparations of Specimens
Thin enough for light to pass through it
Fixationc- cut thin and soak
Embedded - liquid wax or plastic and hardened
sliced or sectioned
microtome - instrument for slicing
Glass slide and stained
Vital stains - do not kill cells
The Phase-Contrast Microscope
A special compound microscope that allows the details within living specimens to be seen without staining
Enhances the differences
The Stereomicroscope
Light that is used to study the external or surface structures of specimens
Three dimensional image
Image not reversed
dissections
TEM- Transmission Electron Microscope
SEM- Scanning Electron Microscope
Laboratory Techniques
Centrifugation
Microdissection
Tissue Culture
Chromatography
Electrophoresis
Spectrophotometry
spectrophotometer
Computers
MRI, CAT
2-2 Section Reviews answers