Which is the best example of organisms that have been naturally selected

Which system revise and send electrical signals throughout the body

The negative impacts of nonnative species generally outweigh the positive impacts

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.