Carbon dioxide makes up less than 1 percent of Earth's atmosphere, and oxygen makes up
about 20 percent. These percentages are maintained most directly by
A)
respiration and photosynthesis
the ozone shield
C)
synthesis and digestion
D)
energy recycling in ecosystems

Glucose, also called grape sugar, blood sugar or corn sugar, is among the simplest and one of the primary naturally occurring sugars. produced naturally by plants as the primary photosynthesis product, it is heavily used by living beings as a main energy source and is necessary for cellular respiration. chemically, it is a monosaccharide carbohydrate and serves as a building block for complex sugars like starch.