Line graphing is an important skill in biology.  Graphs allow one to see relationships between numerical data and to more easily analyze data.   There is always at least one line graph on the Living Environment Exam.  Use the following guidelines to construct graphs in biology.

 I. Tools
      * pencil and a ruler

II. Choose Axes
* Place the independent variable on the x axis (horizontal axis or abscissa)
* Place the dependent variable on the y axis (vertical axis or ordinate)
note: The independent variable is usually the one that the person running the experiment can alter.

II. Choose Scales for Each Axis
* label the scale with the name and unit (ex. seconds) of the variable being plotted
* divide the axis into equal increments
* scales should increase toward the right and toward the top of the graph
* use as much of the graph paper as possible (spread out your data)

III. Choose a Title
 * write title at the top of the graph
* show relationship between the independent and dependent variables
example:
“The dependent variable (Y) as a function of the independent variable (X)”
            or
“The dependent variable (Y) based on the independent variable (X)”

IV. Plotting Points
* plot points as small dots surrounded by a circle
* When plotting a second set of data points on the same grid, surround the     second set of points with small triangles or squares and make a key in the corner of the graph explaining the symbolism of each set of points.

 V. Drawing the Curve

A) Linear Relationships
* best fit lines
* use a straight edge and draw a line that represents an average value

B) Non-Linear Relationships
* curve fitting
* connect points with a smooth curve so the points average around the line as well as possible

C) Random Data –
 * use a straight edge and connect points with straight lines

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