What can cause a reduction in dissolved oxygen levels in an ecosystem? A. an increased load of animal waste B. there is no exact cause C. fewer pesticides in the water D. improved water health​

Average annual precipitation and are the two major features that define the biomes on earth.

Adigestive system that is a series of tubes beginning at the mouth and ending at the anus is a digestive system.

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?