The curve on the left shows the height of a population of penguins the curve on the right shows the population five years later what has happened to this population?
a. stabilizing selection
b. disruptive selection
c. directional selection
d. polygenic selection

In an experiment examining the effects tai chi on arthritis pain, callahan (2010) selected a large sample of individuals with doctor-diagnosed arthritis. half of the participants immediately began a tai chi course and the other half (the control group) waited 8 weeks before beginning. at the end of 8 weeks, the individuals who had experienced tai chi had less arthritis pain that those who had not participated in the course.