Describe how water quality changes from the source of a river to the mouth.

What are the doorways into and out of cells, attached to the membrane, and built in the rough er.

Why do leaves change color in the fall? green pigments break down and no longer mask the color of chlorophyll. chlorophyll breaks down and no longer masks the colors of other pigments. red- and yellow-colored pigments grow and mask green-colored chlorophyll. green-colored chlorophyll breaks down and turns red and yellow.

Explain why biological control methods are generally environmentally superior to chemical pest control methods.