This is a two-part paper-based in-class activity for a class of any size that deals with the concept of growth curves. Given a set of data, students should be able to plot a growth curve and calculate the doubling time and growth rate. Students then predict how the growth rate will be affected by changing nutrients, oxygen, and physical conditions (such as pH, temperature, and salt). Students will demonstrate that they have successfully learned the exercise objectives when they can plot the growth curve, calculate the growth rate, and predict the changes in the growth curve given new information. The understanding of the growth curve concept may be assessed by exam questions.