Usually located at an average altitude of 50 to 80 kilometers above the Earth's surface. Mesotrophic Lake Lake with a moderate nutrient supply. Also see eutrophic lake and oligotrophic lake . Metabolism Describes all of the enzymatic reactions performed by the cells of an organism. Metal A mass of material that is composed of a single element that is characterized by specific characteristics of opacity, ductility, conductivity, and luster.
Some common metals are copper, silver, and gold.
Metamorphic Rock A rock that forms from the recrystallization of igneous , sedimentary or other metamorphic rocks through pressure increase, temperature elevation or chemical alteration. Metamorphism Process that creates metamorphic rocks . The spread of malignant cancer cells to other parts of the body. The scientific study of the atmosphere and its associated phenomena. Methane Methane is very strong greenhouse gas found in the atmosphere.