Energy in ecosystems must be continuously supplied by the sun as the warmth from the sun allows plants to grow plus photosynthesis depends on the sun's energy also. Animals also depend on the sun for warmth to survive (or else hibernate). Also, the sun powers the water cycle, the carbon cycle and the nitrogen cycle
It is only nucleotide phosphates e.g. adenosine triphosphate (ATP) that stores energy for all cell's use. It is also a molecule that is similar to one of the nucleic acids in DNA and RNA.
ln most cases inorder to obtain the mass of a liquid one measures the mass of both the liquid and the container it is in and after wards remeasures the container alone and later subtract the mass of the container alone from the total mass of both the container and the liquid