In a successional community, some kinds of organisms like fungi or beetles are present in every stage of succession. however, the particular species of fungi or beetles that may be there at the earliest stages of succession are often not the same species present in the last successional stage. this is a result of:

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.