What is the main difference between primary and secondary
ecological succession?

Some plants rely on the wind to reproduce an example is it’s important for plants to use the forces of nature to reproduce because 1. 1a white tuft of dandelion seeds 2a spiked burrs surrounding seeds 3a hard shell on a walnut? 2. 1b require pollination to reproduce 2b reproduce only asexually 3b cannot move about freely?

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.

Ivan is looking at a cross section of a stem taken from a vascular plant. he sees two different types of vascular tissue: the xylem, which is closer to the center of the stem, and the phloem, located around the xylem, closer to the outside of the stem. how do these two structures work together in a living plant?