Campbell Biology 11th Edition by Lisa Urry,Michael Cain,Steven Wasserman,Peter Minorsky,Jane Reece

Exercise 10

Interpreting a Scatter Plot with a Regression Line
How Does the Carbonate Ion Concentration of Seawater Affect the Calcification Rate of a Coral Reef Scientists predict that acidification of the ocean due to higher levels of atmospheric CO₂ will lower the concentration of dissolved carbonate ions, which living corals use to build calcium carbonate reef structures. In this exercise, you will analyze data from a controlled experiment that examined the effect of carbonate ion concentration ([
]) on calcium carbonate deposition, a process called calcification.
How the Experiment Was Done For several years, scientists conducted research on ocean acidification using a large coral reef aquarium at Biosphere 2 in Arizona. They measured the rate of calcification by the reef organisms and examined how the calcification rate changed with differing amounts of dissolved carbonate ions in the seawater.
Data from the Experiment The black data points in the graph form a scatter plot. The red line, known as a linear regression line, is the best-fitting straight line for these points.
When presented with a graph of experimental data, the first step in analysis is to determine what each axis represents. (a) In words, explain what is being shown on the x -axis. Be sure to include the units. (b) What is being shown on the y -axis (including units) (c) Which variable is the independent variable-the variable that was manipulated by the researchers (d) Which variable is the dependent variable-the variable that responded to or depended on the treatment, which was measured by the researchers (For additional information about graphs, see the Scientific Skills Review in Appendix F.)