Mutation rates are similar in Bacteria and Archaea, yet under certain stressful conditions mutation rates increase. Why is the mutation rate not constant and close to zero all of the time

This part insulates the reaction chamber from the transfer of heat to or from the surrounding environment

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?

What is the most common structure of volcanoes?