Which process has the greatest effect in determining which members of a population are the most likely to survive until reproductive age?

Apart of an ecosystem that can restrict the growth of a population is referred to as

Any sound above what db can cause hearing loss in human beings

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?