1 1 introducing biology 1.4 the scientific method we study the natural world using the scientific...

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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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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


Scientific methodAnimation 1.1

Flies move around fresh meat, and maggots ( 蛆 ) appear after a few days.

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2 Asking a question

Scientific method

Why are maggots found on rotting meat?

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3 Proposing a hypothesis

Scientific method

My hypothesis (假說 ) is ‘the flies produce the maggots’.

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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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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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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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5 Doing experiments

Experimental set-up


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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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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5 Doing experiments

Experimental set-up


Scientific method

After a few days

Control (對照 ) set-up

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5 Doing experiments

Experimental set-up

Scientific method

maggots appeared

no maggots

Control (對照 ) set-up

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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


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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


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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.


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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.


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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?


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Introducing biology

Hypothesis

Propose a hypothesis to the problem.

The presence of rice speeds up the ripening of papayas.


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Introducing biology

1 How can the hypothesis be tested?

Principle behind the design

rice

raw papayas

two identical boxes


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Introducing biology

1 How can the hypothesis be tested?


Compare the degree of ripening of the two papayas over a period of time.


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Introducing biology

2 According to the hypothesis, predict the results of the investigation.


ripens more quickly


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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.



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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.



Yes.

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Introducing biology

5 What assumption is made in this investigation?

The two papayas are identical.



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Introducing biology

Procedure

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identical transparent plastic boxes

rice


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Introducing biology

Procedure

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raw papayas

cover


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 …


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Introducing biology

Procedure

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take photos everyday to record their changes


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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


Results

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Introducing biology

The presence of rice does not speed up the ripening of papayas.


Conclusion

1 1 introducing biology 1.4 the scientific method we study the natural world using the scientific...

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