Nature of Science Unit Notes
-Scientific Method
-Measurement
-Graphing
-Safety
-Characteristics of Life
-Microscope
The Scientific Method
-Organized common sense
approach to asking an answering
questions.
-A way to address a problem and
reach a solution to the problem.
Step 1: Observe and state a
problem or question
• Will my BioBird twirl more times if it …
• Will my BioBird twirl fewer times if it…
Step 1.5: Research
• Learn something about your topic so
that you can make predictions about the
outcomes of experiments based in
facts, not guesses!
Step 2: Form a hypothesis
• Hypothesis - a proposed, scientifically
testable explanation for an observed
phenomenon.
• Can be dis-proven (rejected) but never
proven (only can be supported).
• Is an “If… Then…” statement!
Hypotheses must be
measurable and compared to
a control
• Bad:
– If a small biobird is dropped, then it will
twirl differently.
• Good:
– If a small biobird is dropped, then it will
twirl 3x as many times as a control bird.
– If a large biobird is dropped, then it will twirl
half as many times as a control bird.
Step 3: Test the hypothesis
• Must use a controlled experiment.
– Allows researcher to test the effects of a
single factor, or experimental variable.
Step 3: Test the hypothesis
• A controlled experiment uses two set-ups to
ensure any differences are due to the
experimental variable:
– Control setup – kept constant
– Experimental setup --contains the variable
• Independent variable - “I control” - plot on X axis
• Dependent variable - “Data collected” - plot on Y axis
Step 4: Record and analyze
data
• Data - observations and information
collected during an experiment.
– Data Tables - where the numerical data
you collect is placed.
• Graphs- easy to interpret, visual
representations of data in tables.
Quantitative vs. qualitative
data
• Quantitative data is measurable,
numerical information collected in an
experiment.
– Examples: length, height, volume, mass
• Qualitative data can be observed but
not measured.
– Examples: color, smell, taste, appearance
Direct vs. indirect evidence
• Direct evidence (observations) –
information about a situation that is
definite and based on
observations.
– The boy is typing.
• Indirect evidence (inferences) –
the result of a mental process
where information is assumed or
inferred about a situation.
– The boy is writing an essay.
– The boy is updating his Facebook page.
Accurate vs. precise data
• Accurate – closeness of measurements of a
quantity to the quantity’s actual value.
• Precise – the degree to which repeated
measurements under unchanged conditions
show the same results (a measure of
reproducibility).
Step 5: Form a conclusion
• Support or reject your hypothesis.
– Cannot be proven!
• **Not all hypotheses are correct!**
Step 6: Replicate the work
• By repeating several times yourself or by others or by
using more samples.
• A hypothesis becomes a scientific theory when it is
tested and confirmed often enough that it is unlikely
to be disproved in future tests.
– Scientific theory - provides a system of assumptions,
accepted principles, and rules of procedure devised to
analyze, predict, or otherwise explain the nature or behavior
of a specific set of phenomena.
• A theory becomes a scientific law when it can’t be
disproved.
– Scientific law - generalizes a body of observations. At the
time it is made, no exceptions have been found to a law. It
explains things but does not describe them; serves as the
basis of scientific principles.
• Remember, there is no “absolute truth” or proof in
science!
Metric Conversions
Ladder Method
The metric system
• Decimal based system - scaled on multiples of 10
• AKA the International System of Units, or SI
• Two ways to solve conversion problems:
– Ladder method
– Dimensional Analysis
Ladder Method
1
2
KILO
1000
Units
3
HECTO
100
Units
DEKA
10
Units
DECI
0.1
Unit
Meters
Liters
Grams
How do you use the “ladder” method?
1st – Determine your starting point.
2nd – Count the “jumps” to your ending point.
3rd – Move the decimal the same number of
jumps in the same direction.
CENTI
0.01
Unit
MILLI
0.001
Unit
4 km = _________ m
Starting Point
Ending Point
How many jumps does it take?
4. __. __. __. = 4000 m
1
2
3
Metric Conversions - Dimensional Analysis
Question: 8400mg = ___?___g
Steps:
1. Know the conversion factor (there are 1000mg in 1g).
2. Set up a multiplication problem and cancel out units on
the top and bottom of the fractions.
3. Do the math to find the answer (8.4g).
Graphing
• Graph- pictoral representation of the
information recorded in a data table.
• Two common types:
– Line graph
– Bar graph
Graphs must have…
• A title
• Properly located and labeled X and Y
axes
• Units on X and Y axes
• Legends
Science Lab Safety
Lab Safety Video:
http://www.flinnsci.com/teacher-resources/teacher-resource-videos/bestpractices-for-teaching-chemistry/safety/laboratory-safety-challenge/
Safety Symbols
Flame
Poison
Dangerous Fumes
Wear Safety Goggles
Electrical Shock
Safety Rule #1
 Never perform any unauthorized
experiments or use any equipment or
instruments without proper instruction.
 Always follow all directions given by
your teacher!
Safety Rule #2
 Do not begin working on your lab unless
your teacher is present!
Safety Rule #3
 When required, proper eye protection
must be worn during the entire class
period!
Safety Rule #4
 When something breaks or spills, you
must notify your teacher so it can be
cleaned up properly.
 DO NOT TRY TO DO THIS YOURSELF!
Safety Rule #5
 When working on a lab, dangling
jewelry should be removed and long hair
should be tied back.
Safety Rule #6
 Do not eat or drink anything in the lab
at any time.
Safety Rule #7
 Consider every material used in the lab
as dangerous.
 Avoid inhaling fumes, tasting, touching,
or smelling any chemical unless your
teacher instructs you otherwise.
 Rinse anything that spills on your skin
with water immediately.
Safety Rule #8
 Nothing is to be taken from the
laboratory unless checked out to you in
writing by your teacher.
Safety Rule #9
 Never become involved in horseplay or
practical jokes in the lab.
 Use maturity at all times when working in
the lab.
Safety Rule #10
 Never point a test tube toward yourself
or anyone else.
Safety Rule #11
 Do not put anything in the sink or
garbage can unless instructed by your
teacher.
 Always clean up according to the lab
and teacher’s instructions.
Safety Rule #12
 Note the location of the safety
equipment in and around the classroom.
 Always wash your hands with soap and
water before leaving the lab.
• Sample size – the number of observations or
replicates in an experiment.
• Scientific mechanism – the combination of
components and processes that serve a
common function.
• Scientific principle – a concept based on
scientific laws, believe to be true and
present, where general agreement is
present.
• Bias – a particular preference or point of
view that is personal rather than scientific.
• Science – a body of evidence-based knowledge
gained through observation and experimentation.
• Biology – the scientific study of life.
• Organism - a form of life; an animal, plant, fungus,
protist, or bacterium.
• Characteristics of living organisms include…
–
–
–
–
–
–
–
–
Made of cells
Based on a universal genetic code
Obtain and use energy
Grow and develop
Reproduce
Respond to their environment
Maintain homeostasis
Change over time
Living things are made of cells
• Unicellular – made up of a
single cell.
• Multicellular – made up of
more than one cell; cells work
together.
• Cells are not found in nonliving matter unless it was
once alive.
Reproduction is necessary for
the survival of a species
• Sexual
reproduction –
requires two cells
from different
individuals to unite.
• Asexual
reproduction –
single organism can
reproduce alone.
Living organisms grow and
develop
• Growth – adding new material or matter
to add to or replace existing parts that
wear out.
• Development – cycle of changes that
eventually lead to aging.
Metabolism is the way
organisms obtain and use
energy
• Must get energy from their environment or
surroundings.
• Must use energy to grow, develop, &
reproduce.
• Plants-obtain energy from the sun during
photosynthesis.
• Animals-take in energy in the form of food.
– Use oxygen to make the sugars in food into
energy, releasing carbon dioxide and water.
Ways to obtain and use
energy
• Anabolism-process of a living organism
synthesizing complex substances from
simpler substances.
– Often powered by ATP (uses energy).
– Used to build bone, muscle, etc.
• Catabolism-breakdown of complex
substances into simpler ones resulting in the
release of energy.
– Way you acquire energy from food.
• Metabolism-sum of all chemical reactions in
the body (anabolism + catabolism).
Living organisms respond to
their environment
• Can be rapid (changes in behavior) or can be
slow (changes in metabolism or growth).
• Stimulus-anything in the environment that
causes and organisms to react.
–
–
–
–
–
–
Light
Temperature
Odor
Sound
Heat
Pressure
Responding to the
environment
• Irritability-ability of living things to react to
stimuli.
– Both plants and animals exhibit this behavior.
• Homeostasis-the process by which
organisms respond to stimuli in ways that
keep conditions in their bodies suitable for
life.
– Ability to maintain constant/stable conditions
necessary for survival.
– Ex. thermostat
Other characteristics of living
organisms include…
• Evolutionary change – over many
generations, groups of organisms
evolve or change over time.
• Universal genetic code – all organisms
store the information they need to live,
grow, and reproduce in a genetic code
written in a molecule of DNA.
Electron Microscopes
• Used to observe VERY small objects that
require going beyond the limit of resolution of
a compound light microscope.
– Transmission electron microscopes (TEMs)shine beam of electrons at sample and magnify
the image.
– Scanning electron microscopes (SEMs)-beam
of electrons scan across surface of object;
electrons that bounce off specimen are detected
to generate the image.
Capillary
Plant cell
Mitochondria
TEM images
Hypodermic Needle
Velcro
Bedbug
SEM images
Red blood cells
Cobweb
Compound Light Microscopes
• Frequently used tools of biologists.
• Magnify organisms too small to be
seen with the unaided eye.
• To use:
– Sandwich specimen between transparent
slide and thin, transparent coverslip.
– Shine light through specimen into lenses
of microscope.
• Lens closest to object is objective lens.
• Lens closest to your eye is the ocular lens.
• The image viewed through a
compound light microscope is formed
by the projection of light through a
mounted specimen on a slide.
How does a compound light
microscope work?
• Video tutorial
Eyepiece/
ocular lens
Nosepiece
Objectives/
objective lens
Stage Clips
Stage
Diaphragm
Diaphragm
Light
Source
Arm
Coarse
Adjustment
Fine Adjustment
Positioning knobs
Base
Always carry a microscope with one hand holding the
arm and one hand under the base.
Magnification
• The process of enlarging something in
appearance, not actual physical size.
What’s my power?
To calculate the power of magnification or total magnification,
multiply the power of the ocular lens by the power of the objective.
Power of Ocular lens X power of Objective
10 X 40
= 400
Comparing Powers of Magnification
We can see better details with higher the
powers of magnification, but we cannot see
as much of the image.
Which of these images
would be viewed at a
higher power of
magnification?
Resolution
• The shortest
distance between
two points on a
specimen that can
still be
distinguished as
two points.
Limit of resolution
• As magnifying power increases, we see
more detail.
• The point where we can see no more
detail is the limit of resolution.
– Beyond the limit of resolution, objects get
blurry and detail is lost.
– Use electron microscopes to reveal detail
beyond the limit of resolution of a
compound light microscope!
Field of view
• The diameter of the circle of view when
you look down the microscope.
What happens to the size of the field of view as you increase
magnification?
Proper handling technique
1. Carry microscopes
with one hand on the
arm and one
supporting the base.
2. Carry microscopes
vertically.
3. Use proper focusing
techniques at all
times!
Proper focusing technique
1.
2.
3.
4.
5.
Check that the lighting is on.
Make sure the objective lens is on low power.
Place the slide on the center of the stage.
Keep both eyes open.
Without looking through the ocular lens, move the
stage using the coarse adjustment knob to bring the
slide as close to the low power objective lens as
possible.
6. Look through the eyepiece & FOCUS DOWN by
turning the coarse adjustment knob away from you
until the specimen is in focus.
7. Fine tune the focus with the fine adjustment knob.do not use the coarse adjustment knob after this
point!
Proper focusing technique,
contd.
8. To magnify the specimen, move the objective lens
to medium power. The specimen may appear
cloudy when viewed. Use the fine adjustment knob
to refocus.
9. To further magnify the specimen, move the
revolving nosepiece to medium. If you focused
properly, you will not hit the slide! Use the fine
focus knob to refocus.
10. When finished with the slide, wash the slide right
away. Move the objective from high to medium
power and from medium power to low power.
11. Once low power is locked in place, lower the stage
using the coarse adjustment knob.
12. Remove the slide from the stage.
13. Properly store the microscope.
Proper clean up technique
1.
2.
3.
4.
5.
Clean up right away
Go back to low power
Lower the stage
Remove the slide
Proper storage
1.
2.
3.
4.
Check the stage
Check the objective
Wind the cord
Dust cover it
Proper storage technique
1. The stage must be all
the way down.
2. The low power
objective must be in
place.
3. The slide must be
removed.
4. The cord must be
wound around the
base.
5. The dust cover must
be replaced.
How to make a wet-mount slide …
1 – Get a clean slide and coverslip.
2 – Place ONE drop of water or stain in the middle of the slide. Don’t use too
much or the liquid will run off the edge! Place the specimen in the drop.
3 – Place the edge of the cover slip on one side of the liquid drop.
4-Hold the coverslip at a 45-degree angle in the edge of the puddle.
5 - Slowly lower the cover slip on top of the drop with fingers
Cover
Lower
or forceps.
Slip
slowly
5 – Remove bubbles by gently tapping. Dry the bottom and sides of the slide.
6 - Place the slide on the stage and view it first with the low power objective.
Wash and dry the coverslip and slide when finished.
You do not need to use the stage clips
when viewing wet-mount slides!