The Nature of Science

Biology 20

What is Science?

• An activity devoted to making sense out of events in the natural world that often seem unrelated and confusing.

• In science, what we claim to know depends on connections between what we observe and what we think we already know.

• In every experiment there is always a control group and experimental group. What is the difference?

Essential Skills to Experimentation

Control Group Experimental Group

Essential Skills: Variables

• Most scientific experiments have a specific set of variables. These are: – Manipulated variable – Responding variable – Controlled variables

Essential Skills: Variables

• Manipulated Variable –• The variable that is being

“tested”• Responding Variable –

• The results• Control Variable –

• Factors that need to stay the same

smoking

Level of health

Age, sex, # of people, health, exercise, diet, length of time, type of smokes, amount smoked.

Essential Skills: Hypothesis and Prediction• An hypothesis is an educated

prediction according to a known scientific concept. An hypothesis must be testable. On the other hand, a prediction is a statement about the way things will happen in the future, often but not always based on knowledge or experience.

Essential Skills: Evidence (Data Collection)Types of Data:

Qualitative dataQualitative data

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Quantitative dataQuantitative data

Qualitative vs. Quantitative

Qualitative data- Uses descriptions or words- Observed with the senses

Examples:

Quantitative data- Uses direct measurements- Determined using an instrument or by counting

Examples:

Essential Skills: Data Analysis• Data collected is generally manipulated,

transformed and presented in a form suitable for evaluation

• Analysis of data includes:– Graphs– Tables– Labeled drawings

Line Graph Used when time is the manipulated variable

Bar Graph Used for comparisons (categories of data)

Rules for GraphingRule # 1:• The title of the graph is written across the top of

the graph paper. It is stated to indicate the relationship between the manipulated variable and the responding variable. The word "versus” should not be included.

Rules for GraphingRule #2:• On the horizontal axis place the name of the

manipulated variable and its unit of measure.

Rule #3:• 3. On the vertical axis place the name of the

responding variable and its unit of measure.

Rules for GraphingRule # 4:• Calculate the values for the scales

so the plotted data extends over most of the graph. All plotted points must fit on the graph paper.

Rule # 5:• In most cases the scales should

start at zero. • If not, use the zigzag at the start of

the axis

X

Y

Manipulated variable

Responding Variable

Rules for GraphingRule # 6:• Plot the coordinate points for the manipulated and

responding variables on the graph and connect the dots.

Rule #7:• If you are plotting two or

more variables, a legend should be placed in the lower right corner of the graph. The legend should identify each of the lines on the graph.

Practice Questions:

A. You keep track of the average price of gas per week over a one year period.

(____) average price of gas per week (____) week What type of graph would work best to show the trend of gas prices? _______________

B. You measure the amount of toxin found in various animals found in the Pacific Ocean.

(____) amount of toxin (____) type of animalWhat type of graph would work best to show amount of toxin is animals? ____________

For each of the following decide which of the variables would be placed on the x axis and which would be placed on the y axis.

YX

Line

YX

Bar