How Does Science Work, Anyway?

CHAPTER 2: BIOLOGY AS A SCIENCE

Biology as a Science

• Science…– Is the investigation of the natural word in such

a way to explain events, and make useful predictions

– Uses the scientific method – Uses data gathered from observations to

make inferences

GROUP WORK:

MAKING OBSERVATIONS AND INFERENCES

Biology as a Science

Information you gather with your

senses

Observation

Logical conclusions based on

observations

Inference

The Scientific Method

The scientific method is an organized way to solve a problem using

prediction and experimentation

Steps of the Scientific Method

Steps of the Scientific Method

1. Make observation & State the problem• Formulate a question that needs to be answered

3. Propose a hypothesis

• A hypothesis is an educated guess about what the solution to the problem is.

• If…then… statement

• Independent Variable: What the scientist is testing

2. Research the problem• Conduct a research plan to find available

information

Problem

Hypothesis

Steps of the Scientific Method4. Conduct an experiment

• Controlled Experiment: an experiment with a control and an experimental group, with several constants

DOES NOT RECEIVE THE INDEPENDENT VARIABLE (WHAT THE SCIENTIST IS

TESTING)

DOES RECEIVE THE INDEPENDENT VARIABLECONTROL

EXPERIMENTAL

QUALITIES KEPT THE SAME BETWEEN BOTH THE CONTROL AND THE EXPERIMENTAL GROUP; REMOVES

OTHER EXPLAINATIONS FOR THE RESULTS

CONSTANTS

Test the Hypothesis

experimental control group group

Constants:

Experimental Group Control Group

Steps of the Scientific Method5. Observations and data.

• Observations are made with our senses and instruments; the data is measureable• Data measured with numbers is quantitative • Data measured with words is qualitative

• Often the data or results of the experiment is called the dependent variable

• Dependent Variable: the aspect of an experiment that changes (as time passes), the data being collected• Graphed in the y-axis

Observations & Data

Steps of the Scientific MethodAs data is collected, it must be organized in a data table,

diagram, chart or equation.Data is interpreted by a graph. Graphs organize data tables

and make results more clear.

Control Group - plant height

Experimental Group - plant height

Day 1

0.0 cm 0.0 cm

Day 2

0.2 cm 0.5 cm

Day 3

0.3 cm 0.9 cm

Day 4

0.5 cm 1.3 cm

Day 5

0.7 cm 1.7 cm

1 2 3 4 50

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

Fertilizer Effect on Plant Growth

Control GroupExperimental Group

Day

Pla

nt

Heig

ht

(cm

)

Steps of the Scientific Method

6. Analysis & Conclusions

• The data from the experiment needs to be looked at and analyzed.

• Conclusion: determines if the stated hypothesis was supported by the results

7. Repeat Experiment & Report• Results are only valid after other scientists have

repeated the experiment several times and get the same results

• Research reports must be peer reviewed and can be published in scientific journals

Report and Repeat

Repeat your experiment to make sure you get the same results.

Tell other tomato growers about your results and let them try the experiment to see if they get the same results.

Scientific Explanations…• are TENTATIVE• can become a THEORY• are SHARED with other scientists

• are NOT BIAS

How Does Science Work, Anyway?

Designing a GOOD Controlled Experiment

1. Have two groups: control and experimental

2. Have ONE independent variable

3. Perform several trials (trial: an experiment’s test)

4. Have a large sample size (subjects in the experiment)

5. Have as many constants as possible

6. Have a detailed Data Table

RESEARCH HOW THIS SCIENTIST USED THE SCIENTIFIC METHOD:

LOUIS PASTEUR’S SPONTANEOUS GENERATION EXPERIMENT

What was the QUESTION he was trying to answer?

What was his HYPOTHESIS?

Describe his EXPERIMENT.

Explain his RESULTS.

What CONCLUSIONS did he make?

Louis Pasteur’s Spontaneous Generation Experiment

• http://bcs.whfreeman.com/thelifewire/content/chp03/0302003.html

2005-2006

Examples of experiments 1 • How does fertilizer affect the growth rate

of plants?– we set up an experiment testing different

amounts of fertilizer on different plants & measuring the growth (height) of the plants:

• dependent variable (Y-axis)?

• independent variable (X-axis)?

The effect of _____________on _____________

2005-2006

Examples of experiments 2 • How does exercise affect heart rate of

10th grade student?– we set up an experiment testing different

lengths of time of exercise (minutes) on the heart rate of students:

• dependent variable (Y-axis)?

• independent variable (X-axis)?

The effect of _____________on _____________

2005-2006

Examples of experiments 3 • What’s the favorite drink of students?

– we set up an experiment surveying students and asking which is their favorite drink :• dependent variable (Y-axis)?

• independent variable (X-axis)?The effect of _____________on _____________