Mainly the molecules used in the Calvin Cycle are from the light reactions prior to it, and therefore, the ATP energy made in the light reaction fuels the Dark Reaction which will eventually form Glucose
carbon dioxide
Water
naDH
Why is photosynthesis essential to animals?
# photosynthesis 2. Water is the source of hydrogenduring the light dependent reaction of photosynthesis. Water is split into hydrogen and oxygen. The oxygen is released into the atmosphere and the hydrogen is transferred to a carrier molecule called NADP, to produce NADPH. The NADPH is then used in the light independent reaction to reduce carbon dioxide to carbohydrate. See my answer to this question on WikiAnswers: What connects the light dependent reaction to the light independent reaction?
Water is the molecule that is split during the light reaction of photosynthesis when releasing oxygen.
Water is the molecule that is split during the light reaction of photosynthesis when releasing oxygen.
Water 
Why is photosynthesis essential to animals?
With the production of one molecule of sugar six molecules of oxygen are produced during photosynthesis.
photosynthesis is the process of a plant making food.
The Mitochondria of an animal cell is responsible for producing ATP in an animal while the Chloroplast of a plant cell is responsible for producing ATP in a plant. More specifically, for plants, the Glucose which is produced in the light stage of photosynthesis (C6H12O6) is responsible for the production of adenine triphosphate (ATP), which is where a plant gets the energy to produce food in the dark stage of photosynthesis. The answer you are looking for is Glucose. The Glucose molecule is most responsible for the production of ATP.
Water is the molecule that is split during the light reaction of photosynthesis when releasing oxygen.
Oxygen
chlorophyll
Photosystem
chlorophyll
CO2
6 molecule of oxygen and water,1 molecule of glucose.
# photosynthesis 2. Water is the source of hydrogenduring the light dependent reaction of photosynthesis. Water is split into hydrogen and oxygen. The oxygen is released into the atmosphere and the hydrogen is transferred to a carrier molecule called NADP, to produce NADPH. The NADPH is then used in the light independent reaction to reduce carbon dioxide to carbohydrate. See my answer to this question on WikiAnswers: What connects the light dependent reaction to the light independent reaction?