The replacement stage of b by stage c and the replacement of stage c by stage d in a particular location is known as a exploitation b covercropping c ecological succession d punctuated equilibrium

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.