With this biology question

What are the formed elements (cell or parts of cell) in blood and what are their functions ?

Is there any species that went extinct in recent years due to natural causes (not caused by human interaction). if so, what caused it?

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.