Why is it important for dna to be duplicated before mitosis

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.

The law of thermodynamics states that energy can't be created or destroyed. to natural sources of energy on earth are the

After dinner with his brother, charles darwin looked through a book by thomas robert malthus, who believed that humanity, if unchecked, could double its population size in 25 years . why then , wasn't the earth overrun with humans at this point ? how does this relate to the stoning of the darwin's carriage?