What is the name of the nucleotide base substitute for thymine in DNA transcription and what is its purpose? adenine, to make the mRNA strand easily destroyed after use guanine, to make the mRNA strand stronger so it may be used many times uracil, to make the mRNA strand stronger so it may be used many times uracil, to make the mRNA strand easily destroyed after use

What is point source pollution of an aquatic ecosystem? a) pollution of freshwater sources b) pollution from many sources that combine into one c) pollution that occurs over a wide area; water that runs off from fields, parking lots, and other land surfaces d) pollution that can easily be identified with a single discharge source, such as an open pipe which drains into a body of water