Graphing AP Biology

Use Computer Software Excel

Components Title Each line or bar must be easily identifiable Informs the reader about the experiment and tells the reader exactly what is being measured Each line or bar must be easily identifiable Axes must be clearly labeled with units X axis shows the independent variable Y denotes the dependent variable Example: time, light intensity, concentration of a hormone or nutrient DRY MIX = dependent responding on y axis manipulated independent on x axis independent (IV) = what I the scientist manipulated dependent (DV) = responds according to changes made to the independent variable

Component Intervals must be uniform If one square on the x axis equals five minutes, each interval must be the same and not change to 10 minutes or one minute. If there is a break in the graph such as a time course over which little happens for an extended period, it should be noted with a break in the axis and corresponding break in the data line. It is not necessary to label each interval. Labels can identify every 5 or 10 intervals as appropriate Labels on the x and y axis should allow the reader to easily see the information.

Components More than one condition of an experiment may be shown on a graph by the use of different lines. Ex: products in an enzyme reaction at different temperatures can be compared on the same graph. Each line must be clearly diffrentiated from the others by label, different style or colors indicated by a key to aid in comparing the results.

Components Clarify if the data starts at the origin (0,0) or not. The line should not be extended to the origin if the data do not start there! The line should not extend beyond the last data point (extrapolation) unless a dashed line clearly indicates that this is a prediction about what may happen.

Components Error Bars Included in most graphs For counted, measured data Shows standard error (SE) Do not use standard deviation on bar graphs Can be used on scatter plots of means

Components How to create error bars

Types of Graphs Scatterplots Comparing one measured variable against another Looking for trends or associations Plot of individual data points If the relationship is thought to be linear to see corelation Find by linear regression Draw a line showing pattern Draw a line connecting all

Types of Graphs Bar Graph Comparison of populations Measured variables Ex: compare spine length with and without preditors, shape of leaves in or out of sun Measured variables Must include standard error

Types of Graphs Scatterplots continue Plot of manipulated independent x variable against the dependent y variable General shapes/trends=biological implications Bell curve: random samples or normal distributions Concave upward curve: exponential increasing function (early stages of bacterial growth) Sine wave: biological rhythm

Types of Graphs Box and Whiskers

Types of Graphs Hystograms

Source College Board Quantitative Skills Guide page 6-14 http://apcentral.collegeboard.com/apc/public/repository/AP_Bio_Quantitative_Skills_Guide-2012.pdf