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Introducing biology
1.4 The scientific method1.4 The scientific method
1.4 The scientific method
We study the natural world using the scientific method.
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Introducing biology 1.4 The scientific method
I carried out an investigation using the scientific method.
Scientific method
I’m Francesco Redi.
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Introducing biology 1.4 The scientific method
Scientific method
There is NO single scientific method, but it usually involves a few basic steps.
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Introducing biology
1 Making observations
1.4 The scientific method
Scientific methodAnimation 1.1
Flies move around fresh meat, and maggots ( 蛆 ) appear after a few days.
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Introducing biology 1.4 The scientific method
2 Asking a question
Scientific method
Why are maggots found on rotting meat?
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Introducing biology 1.4 The scientific method
3 Proposing a hypothesis
Scientific method
My hypothesis (假說 ) is ‘the flies produce the maggots’.
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Introducing biology 1.4 The scientific method
3 Proposing a hypothesis
Scientific method
Remember that hypotheses are NOT needed in investigations which do NOT require explanations of observations.
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Introducing biology 1.4 The scientific method
4 Making a prediction (預測 )
Scientific method
If my hypothesis is correct, maggots will not appear when I keep the meat away from the flies.
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Introducing biology 1.4 The scientific method
5 Doing experiments
Experimental set-up Control (對照 ) set-up
jar coveredjar not covered
Scientific method
Online video:Redi’s experiment
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Introducing biology 1.4 The scientific method
5 Doing experiments
Experimental set-up
jar coveredjar not covered
Scientific method
identical to experimental set-up except that the factor under investigation (i.e. the visit by flies) is absent
ensure the result is due only to the factor under investigation Control (對照 ) set-
up
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Introducing biology 1.4 The scientific method
Independent variable
Dependent variable
Controlled variables
Scientific method
Whether flies were allowed to reach the meat
Whether maggots appeared on the meat
Size of the meat, size of the jar, temperature, etc.
5 Doing experiments
What Redi changed
What Redi measured
What Redi kept the same
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Introducing biology 1.4 The scientific method
5 Doing experiments
Experimental set-up
jar coveredjar not covered
Scientific method
After a few days
Control (對照 ) set-up
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Introducing biology 1.4 The scientific method
5 Doing experiments
Experimental set-up
Scientific method
maggots appeared
no maggots
Control (對照 ) set-up
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Introducing biology 1.4 The scientific method
6 Drawing a conclusion
Scientific method
The result supports my hypothesis! I conclude that the maggots are produced by the flies.
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Introducing biology
Basic steps of scientific method:
Making observations
Asking a question
Proposing a hypothesis
1.4 The scientific method
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Introducing biology
Basic steps of scientific method:
Making a prediction
Doing experiments
Drawing a conclusion
Hypothesis not supported
New or revised hypothesis
Hypothesis supported
1.4 The scientific method
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Introducing biology
1.51.5 Performing a scientific Performing a scientific investigationinvestigation
raw papaya
rice
Why do papayas ripen more quickly when they are kept in a container with rice?
rice
Mary
1.5 Performing a scientific investigation
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Introducing biology
Task
Design an investigation to find out the answer to Mary’s question.
1.5 Performing a scientific investigation
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Introducing biology
Aim
What is the aim of this investigation?
To study the importance of rice in speeding up the ripening of papayas.
1.5 Performing a scientific investigation
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Introducing biology
Problem to investigate
What is the problem to be investigated?
Why do papayas ripen more quickly if they are kept in a container with rice?
1.5 Performing a scientific investigation
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Introducing biology
Hypothesis
Propose a hypothesis to the problem.
The presence of rice speeds up the ripening of papayas.
1.5 Performing a scientific investigation
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Introducing biology
1 How can the hypothesis be tested?
Principle behind the design
rice
raw papayas
two identical boxes
1.5 Performing a scientific investigation
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Introducing biology
1 How can the hypothesis be tested?
Principle behind the design
Compare the degree of ripening of the two papayas over a period of time.
1.5 Performing a scientific investigation
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Introducing biology
2 According to the hypothesis, predict the results of the investigation.
Principle behind the design
ripens more quickly
1.5 Performing a scientific investigation
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Introducing biology
3 Identify the variables.Independent
variableDependent
variableControlled variables
Whether there is rice in the container
Degree of ripening of the papaya
Initial degree of ripening of the papaya, size of the papaya, etc.
1.5 Performing a scientific investigation
Principle behind the design
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Introducing biology
4 Is it necessary to set up a control?
Why?To confirm that the presence of rice is the only factor that affects the speed of ripening of papayas.
1.5 Performing a scientific investigation
Principle behind the design
Yes.
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Introducing biology
5 What assumption is made in this investigation?
The two papayas are identical.
1.5 Performing a scientific investigation
Principle behind the design
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Introducing biology
Procedure
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identical transparent plastic boxes
rice
1.5 Performing a scientific investigation
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Introducing biology
Procedure
2
raw papayas
cover
1.5 Performing a scientific investigation
Experimental set-up
Control set-up
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Introducing biology
Experimental set-up
Control set-up
Procedure
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Leave for 7 days …
1.5 Performing a scientific investigation
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Introducing biology
Procedure
3
take photos everyday to record their changes
1.5 Performing a scientific investigation
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Introducing biology
Degree of ripening (arbitrary unit)
Day 1
Day 2
Day 3
Day 4
Day 5
Day 6
Day 7
Box with rice 0 1 2 2 3 4 5
Box without rice
0 1 2 2 3 4 5
1.5 Performing a scientific investigation
Results