1 1 Introducing biology 1.4 The scientific method We study the natural world using the scientific method.

1 2 Introducing biology 1.4 The scientific method I carried out an investigation using the scientific method. Scientific method I’m Francesco Redi.

1 3 Introducing biology 1.4 The scientific method Scientific method There is NO single scientific method, but it usually involves a few basic steps.

1 4 Introducing biology 1Making observations 1.4 The scientific method Scientific method Animation 1.1 Flies move around fresh meat, and maggots ( 蛆 ) appear after a few days.

1 5 Introducing biology 1.4 The scientific method 2Asking a question Scientific method Why are maggots found on rotting meat?

1 6 Introducing biology 1.4 The scientific method 3Proposing a hypothesis Scientific method My hypothesis ( 假說 ) is ‘the flies produce the maggots’.

1 7 Introducing biology 1.4 The scientific method 3Proposing a hypothesis Scientific method Remember that hypotheses are NOT needed in investigations which do NOT require explanations of observations.

1 8 Introducing biology 1.4 The scientific method 4Making a prediction ( 預測 ) Scientific method If my hypothesis is correct, maggots will not appear when I keep the meat away from the flies.

1 9 Introducing biology 1.4 The scientific method 5Doing experiments Experimental set-up Control ( 對照 ) set-up jar covered jar not covered Scientific method Online video: Redi’s experiment

1 10 Introducing biology 1.4 The scientific method 5Doing experiments Experimental set-up jar covered jar 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

1 11 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. 5Doing experiments What Redi changed What Redi measured What Redi kept the same

1 12 Introducing biology 1.4 The scientific method 5Doing experiments Experimental set-up jar covered jar not covered Scientific method After a few days Control ( 對照 ) set-up

1 13 Introducing biology 1.4 The scientific method 5Doing experiments Experimental set-up Scientific method maggots appeared no maggots Control ( 對照 ) set-up

1 14 Introducing biology 1.4 The scientific method 6Drawing a conclusion Scientific method The result supports my hypothesis! I conclude that the maggots are produced by the flies.

1 15 Introducing biology Basic steps of scientific method: Making observations Asking a question Proposing a hypothesis 1.4 The scientific method

1 16 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

1 17 Introducing biology 1.5Performing a scientific investigation 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

1 18 Introducing biology Task Design an investigation to find out the answer to Mary’s question. 1.5 Performing a scientific investigation

1 19 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

1 20 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

1 21 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

1 22 Introducing biology 1How can the hypothesis be tested? Principle behind the design rice raw papayas two identical boxes 1.5 Performing a scientific investigation

1 23 Introducing biology 1How 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

1 24 Introducing biology 2According to the hypothesis, predict the results of the investigation. Principle behind the design ripens more quickly 1.5 Performing a scientific investigation

1 25 Introducing biology 3Identify the variables. Independent variable Dependent variable Controlled 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

1 26 Introducing biology 4Is 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.

1 27 Introducing biology 5What assumption is made in this investigation? The two papayas are identical. 1.5 Performing a scientific investigation Principle behind the design

1 28 Introducing biology Procedure 1 identical transparent plastic boxes rice 1.5 Performing a scientific investigation

1 29 Introducing biology Procedure 2 raw papayas cover 1.5 Performing a scientific investigation Experimental set-up Control set-up

1 30 Introducing biology Experimental set-up Control set-up Procedure 3 Leave for 7 days … 1.5 Performing a scientific investigation

1 31 Introducing biology Procedure 3 take photos everyday to record their changes 1.5 Performing a scientific investigation

1 32 Introducing biology Degree of ripening (arbitrary unit) Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7 Box with rice Box without rice Performing a scientific investigation Results

1 33 Introducing biology The presence of rice does not speed up the ripening of papayas. 1.5 Performing a scientific investigation Conclusion