Scientific Method

•Scientists use two main approaches to learn about nature

– Science• Is a way of knowing• Seeks natural causes for natural

phenomena•Discovery Science•Hypothesis Based Science

• Scientists describe some aspect of the world and use inductive reasoning to draw general conclusions

• Scientists attempt to explain observations by testing hypotheses

• Observations, questions, hypotheses as tentative answers to questions

• Deductions leading to predictions, and then tests of predictions to see if a hypothesis is falsifiable

•Questions or statements that are testable through experimentation or observation

•If - then format•Preliminary explanation to problem

Observations

Question

Hypothesis # 1:Dead batteries

Hypothesis # 2:Burnt-out bulb

Prediction:Replacing batterieswill fix problem

Prediction:Replacing bulbwill fix problem

Test prediction Test prediction

Test falsifies hypothesis Test does not falsify hypothesis

•Tests the predictions made by a hypothesis

•Double Blind•Controlled

•One group receives the drug to be tested; One group receives the placebo

•Researchers do not know which subject is receiving the actual drug

•Eliminates the bias that may influence the results

•Experiment isolates a single factor that is directly responsible for an effect.

•Condition in the experiment that differs

•Independent Variable: Variable that is independent of experiment–pH, time, temperature

•Dependent Variable: •What you are testing

–Dependent of results of experiment

•Provides a standard of comparison for the one factor in the experiment that varies

A Case Study of

Hypothesis-Based Science

– In experiments designed to test hypotheses

• The use of control groups and experimental groups helps to control variables

Per

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100

80

60

40

20

0

83%

17% 16%

84%Artificial king snakes

Artificial brown snakes

Coral snakesabsent

Coral snakespresent

Figure 1.8B Figure 1.8C

Figure 1.8D

Figure 1.8E

•Not all science discoveries strictly follow the “scientific method”. Which of the following would best be described as discovery science?

– Sequencing the human genome.– Describing a new bird species from the

Philippines. – A project to find preserved specimens of

the probably extinct Rocky Mountain locust frozen in glaciers .

– All of the above.

•Not all science discoveries strictly follow the “scientific method”. Which of the following would best be described as discovery science?

– All of the above.

•These two snakes look remarkably similar to each other. The coral snake (right) is very poisonous to

vertebrates. Hypotheses:

•H1: The coral snake’s bright color pattern serves to warn off potential predators.

•H2: The king snake suffers less predation because it mimics or looks like the coral snake.

•H3: The protection that king snakes receive by mimicking coral snake will depend on the presence of coral snakes.

•A team of scientists designed an investigation that used artificial snakes to test the previous hypotheses. •Which of the previous hypotheses

are supported by the results displayed at the right?

– H1: The coral snake’s bright color pattern serves to warn off potential predators.

– H2: The the king snake suffers less predation because it mimics or looks like the coral snake.

– H3: The protection that king snakes receive by mimicking coral snake will depend on the presence of coral snakes.

– Both 1 and 2

•A team of scientists designed an investigation that used artificial snakes to test the previous hypotheses.

•Which of the previous hypotheses are supported by the results displayed at

the right?

– Both 1 and 2

•Biologists placed artificial snake mimics in two different localities to test the hypothesis that looking like a poisonous snake only works where the poisonous snake is found:1. Outside of the coral snake range—only king snakes present.2. Inside the coral snake range—both coral and king snakes are present.

•The data graphed at the right __________ the hypothesis that the effectiveness of mimic coloration depends upon the presence of the poisonous model is:

– supports– does not support – is irrelevant to

•The data graphed at the right __________ the hypothesis that the effectiveness of mimic coloration depends upon the presence of the poisonous model is:

– supports

•Based on this data which of the following is a logical hypothesis or prediction?

– King snakes outside of the range of coral snakes will more closely resemble coral snakes than populations of king snake living within the range of coral .

– King snakes outside of the range of coral snakes will not resemble coral snakes as closely as populations of king snakes that live within the range coral snakes.

– Neither prediction is valid.

•Based on this data which of the following is a logical hypothesis or prediction?

– King snakes outside of the range of coral snakes will not resemble coral snakes as closely as populations of king snakes that live within the range coral snakes.