Which aquatic ecosystems are composed of salt water? Select four options.
intertidal zones
neritic zones
open ocean
streams
coral reefs

i think the answer is

mass

biology is the study of life. it is the study of living organism.

amber has allowed scientists to study dna that has been preserved over millions of years.

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.