Transcript Honors Biology Scientific Method Power Point

Scientific Method
and Designing Your Cricket
Experiment
Initial Observation
• Use your senses to observe
-be objective (measure), not
subjective (opinions)
– See, hear, touch, taste, smell,
etc.
• Can also use tools to
measure (label numbers)
– Temperature, length,
volume, etc.
Observations: Two Types
• Qualitative – describe what we observe
– EX: The flower has white petals.
– EX: Bob has blue eyes.
• Quantitative –measure what we observe
– EX: The flower has seven petals.
– EX: Bob has two eyes.
Try to make quantitative
observations out of qualitative ones.
• Qualitative: The dead fish is smelly.
• Quantitative: You could ask a person to rate
the “smelliness” from 1-5.
TIPS FOR GOOD
OBSERVATIONS
1.
2.
3.
4.
Be specific
Use numbers
Use terms others would understand
Avoid using emotions, good/bad, or
opinions
5. This is not the time for critical
evaluations…just state the facts.
Inference
• Reasonable conclusions or a hypothesis
from observations you’ve made.
• Use judgments based on past experiences or
and prior knowledge.
What inference can
you make here?
Which is the better observation?
• It is 58oF in the room.
• It is cool in the room.
• The iguana likes lettuce.
• The iguana consumed 90% of the lettuce.
• The bacteria is yucky.
• The bacteria has a slimy appearance and smells of
sulfur.
Problem Statement:
State the Question
• “What is the effect of the
independent variable on the
dependent variable?”
• What is the independent
variable here?
What is the dependent
variable here?
Which are Better Problem
Statements?
• What is the effect of temperature on the
height of plants grown in soil?
• How tall do plants get?
• Why does that fish always swim to the top?
• What is the effect of oxygen content on the
water on the swimming location of a fish in
a tank?
Observing Crickets
GET A DOZEN CRICKETS WITH A
CUP (hand on top)-Put them in
the tank w/lid, please.
• Make at least 10 observations and 10
inferences
• Write Problem Statements related to the
observation
Obser
vation
1
2
3
4
Infere
nce
Proble
m Stat.
PLAN CRICKET BEHAVIOR
EXPERIMENT
• Laptops, if needed • Plan for the cricket
behavior experiment:
• Refer to your
-problem statement
articles
• -experiment set-up
• (Independent and
Dependent Variables)
• (Block - will run 3
trials, do test run
(Enlarge to read captions)
today)
Hypothesis
• “If…then…” If producing oxygen bubbles
in photosynthesis is related to light color,
then green light will increase
photosynthesis oxygen bubbles to form.
• Independent variable-varied by
experimenter
• Dependent variable-changes as a result of
the independent variable
• Prediction
Hypothesis
• 1. Must be testable – some way to check its
validity
• 2. Must be falsifiable – must be some
experiment that could show that it is not
true (may not prove to be false, just have to
be able to test that)
Can you test these to be falsifiable?
Can you rewrite these to be testable?
• 1. Animals are better than plants.
• 2. The average tree height on the HS
campus is the same as on the MS campus.
• 3. How many angels does it take to dance
on the head of a pin?
Writing a Hypothesis
• Common Hypothesis
•
- educated guess
•
- the general statement
• Formalized Hypothesis - Write the “If … and
then…” format
• DO WORKSHEET TO PRACTICE WRITING
IF…THEN HYPOTHESES
Writing a problem statement and
hypothesis for your cricket behavior tips:
•
•
•
•
Sexual: male vs. female
Phototaxis: how many crickets in diff. light
Stimulus: food or terrain preferences
Courtship: make a chart of beh. (touch,
chirp, face direction, mount)
• Agonistic: make chart of beh. (bite, jump
toward, chirp, etc.)
• Territorial: count crickets in areas (hut,
leaves, by water, by food, by females)
A Controlled Experiment
• Only one tested variable at a time
• Manipulated Variable (Independent
Variable) – one you change
• Responding Variable – (Dependent
Variable)- one that changes as a result
Experiment
A. Independent Variable -what you change
goes on the X-axis of the graph
B. Dependent Variable -what changes as a
result of what you did – goes on the Y-axis
of the graph
Independent Variable?
Dependent Variable?
Experiment
• Constants-all the things in the
experiment that stay the same
same size Petri dishes
Same agar medium
Same type of bacteria
What are some constants here?
What constants are there in this
experiment?
• Control – the part of the
experiment that does not have the
independent variable in it
• Use for reference, comparison
• Often the normal condition (no
food, room light, room temp.)
What is the control?
L-added oxygen
M-control(no gas added)
R-added carbon dioxide
Do you think a placebo is a control?
(inert pill, one without the drug)
• EX: some take Celebrex®, some
take a sugar pill
Run the tests
Record the data
graphs
charts
video
write observations
measurements
Celebrex – Placebo Experiment
Results
• Have we proven that
Celebrex® (without a
doubt) improves
arthritis pain?
• What might be another
explanation? Can we
prove it false?
450
400
350
300
250
200
150
100
50
0
Celebrex
Improve
Same
Placebo
Conclusion
• Agree or disagree
with the hypothesis
• The 10% spray
produced taller
plants.
Repeat the Experiments
Other scientists must be able to
repeat your experiment with
similar results to prove it true. OR
they might prove it false.
NOW YOU WILL DESIGN AND
RUN AN EXPERIMENT
• RECEIVE CRICKET BEHAVIOR
EXPERIMENT HANDOUT
• LAB GROUPS OF 4 (5)
• BEHAVIOR VARIABLE
• PLAN SET-UP
• RUN 3 TRIALS
• WRITE RESULTS
DUE DATES:
•
•
•
•
August 25- (Mon.) – Cricket Fact Sheet
August 25/26 - (M/T)-Observe crickets
August27-29- (w/Th/F)-Design + Run Exp.
Sept. 5 - (Fri.) Cricket Report Due