What is the primary source of freshwater for a river stream

The source of the water in lakes, reservoirs, and ponds may be rivers, streams, groundwater, rainfall, melting snow runoff, or a combination of these. Any of these sources may carry contaminants. Because water exits from these water bodies at a slow rate, pollutants can become trapped and build up.

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.

image result for how many calories of energy will 20 grams of carbohydrates provide in one gram provides 4 calories

consuming the right balance of protein, carbohydrates and fat can you maintain a healthy weight and optimize your energy levels. protein and carbohydrates both contain 4 calories per gram, while fat provides 9 calories per gram.