Transcript Methods of Biology - Wando High School

Methods of Biology
• The series of steps used by scientists to gather
information and answer questions is called the
Scientific Method.
• If you had a question or a problem to solve,
what steps would you go through to resolve it?
7 Steps of the Scientific Method
• Number 1 - State the Problem
– Take note of something no one has seen before or
has yet to explain
7 Steps of the Scientific Method
• Number 2 - Gather Information
– Observation - Gathering information using your senses
– Information gathered should be:
• Credible - trustworthy
• Accurate - correct – based on supported data
• Relevant - applicable, related to the topic of the investigation
– These sources could be
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Previous scientific investigations
Science journals
Textbooks
Other credible sources, such as scientifically reliable internet sites.
Observation vs. Inference
• Inference – making a judgment based upon an
observation and past experience
• Make at least 3
observations
about this picture.
• Make at least 3
inferences about
this picture.
• Make three
observations and
inferences with this
new information
• Does the new
information change
your responses?
What does this final picture do to your previous
inferences?
What does this picture do to your previous
inferences?
7 Steps of the Scientific Method
• Number 3 - Form a Hypothesis
– Create a testable explanation for the situation that
you observed
7 Steps of the Scientific Method
• Number 4 - Test the Hypothesis - Experiment
– Design an experiment
• An organized procedure for collecting information under
controlled conditions
– The experiment will have two groups
• Control – all conditions
are kept the same
• Experimental – conditions
match that of the control
except for the one factor
being tested
7 Steps of the Scientific Method
• Testing…
• An important part in the experiment design is the
sample size – the number of test subjects
– A large sample size increases the reliability of results
– A large sample size decreases the effect of errors on the
outcome
• How could having a larger sample size help the
following experiments?
– Tim tested the effect of fertilizer on two plants.
The one with fertilizer grew taller than the
one without it.
– Suzy developed a drug to lower cholesterol.
She gave it to two patients who later died.
7 Steps of the Scientific Method
• Testing…
– The condition that is changed in the experiment is
the independent variable – it will be the only thing
that can affect the outcome
– The outcome observed is the dependent variable –
it depends upon the changes made to the
independent variable
– Note: Some experiments cannot be controlled so
other observation methods have to be used
• Example: wildlife study
Independent vs. Dependent Variables
• Mark the dependent and independent variable in
each situation
• Suzy wanted to test how changing her diet affected her
weight.
• The track team members that ran extra laps at practice
ran better times at the next meet.
• Jack planted half of his roses in the shade and the other
half in the direct sunlight and measured the differences
in plant height and bloom production.
7 Steps of the Scientific Method
• Number 5 - Record and Analyze Data
– Record Data
• Data – information obtained from experiments
– Observations
– Results
• Data should be precise and accurate
– Precision – the degree to which measurements made in the same way
agree with each other
» If you and I measure it, do we get the same thing?
– Accuracy – the degree to which the value measured agrees with the true
or accepted value
» Even if we both got the same thing, did we measure it correctly?
– Data must then be analyzed or interpreted
• Graphs
• Tables
• Charts
7 Steps of the Scientific Method
• Number 6 - State a Conclusion
– Did the data support the hypothesis?
• If yes…
– Verify results
» Can the experiment be repeated?
» Do other scientists support the findings?
• If no…
– Repeat the experiment
– Revise the experiment
– Develop a new hypothesis
7 Steps of the Scientific Method
• Number 7 - Repeat
– No matter what happened!
– Fact – Observable phenomenon that can be
confirmed by scientists many times
– Form a Theory – a hypothesis tested over a long
period of time, supported by separate experiments
Fact vs. Theory
• Which is Fact…Which is Theory?
– Dinosaurs were cold blooded.
– The caterpillar is 3.5 cm long.
Using the Scientific Method
• You haven’t been catching as many fish as you
used to at your best fishing spot
• Your friend tells you that you and your brother
smell funny
Identifying Study Components
A student noticed that when a dog is cut, the dog periodically licks its wounds. Usually after a few
days, the wound begins to heal without ever showing signs of infection. The following steps
outline the student's line of reasoning:
A. I wonder why the dog's wound doesn't become infected.
B. The dog's saliva must prevent the growth of infection-causing bacteria.
C. I'll obtain a bacterial culture and grow the same kind of bacteria in two identical culture dishes.
Once the bacteria start growing, I'll add dog saliva to only one of the dishes and leave the other
alone. I'll cover both dishes. Then I'll observe what happens each day for a week.
D. Even after adding the dog saliva to one of the dishes, the bacteria continued to grow in both
dishes over the course of the week. However, the bacteria in the treated dish grew more slowly
than the bacteria in the untreated dish.
E. I think I'll try something else. I'll start with two identical culture dishes, as before, and use the
same kind of bacteria in each dish, but this time I'll treat one dish with dog saliva before I add the
bacteria. I'll observe what happens each day for a week.
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What was the student’s hypothesis?
Which step described the experimental set up?
Identify the control
What is the independent variable?
What is the dependent variable?
What data did the student collect?
What is a possible conclusion from this experiment?
Is that conclusion a fact or an inference?
Identifying Study Components
A student noticed that when a dog is cut, the dog periodically licks its wounds. Usually after a few
days, the wound begins to heal without ever showing signs of infection. The following steps
outline the student's line of reasoning:
A. I wonder why the dog's wound doesn't become infected.
B. The dog's saliva must prevent the growth of infection-causing bacteria.
C. I'll obtain a bacterial culture and grow the same kind of bacteria in two identical culture dishes.
Once the bacteria start growing, I'll add dog saliva to only one of the dishes and leave the other
alone. I'll cover both dishes. Then I'll observe what happens each day for a week.
D. Even after adding the dog saliva to one of the dishes, the bacteria continued to grow in both
dishes over the course of the week. However, the bacteria in the treated dish grew more slowly
than the bacteria in the untreated dish.
E. I think I'll try something else. I'll start with two identical culture dishes, as before, and use the
same kind of bacteria in each dish, but this time I'll treat one dish with dog saliva before I add the
bacteria. I'll observe what happens each day for a week.
•
•
•
•
•
•
•
•
What was the student’s hypothesis?
Which step described the experimental set up?
Identify the control
What is the independent variable?
What is the dependent variable?
What data did the student collect?
What is a possible conclusion from this experiment?
Is that conclusion a fact or an inference?