Starch molecules present in a maple tree are made from materials that originally entered the tree from the external environment as

Starch molecules present in maple tree from the external environment as INORGANIC COMPOUNDS.
Starch is made in the maple tree during the process of photosynthesis. The inorganic substances that are used during the process of photosynthesis are carbon dioxide and water; these two are mixed together in the presence of sunlight to form carbohydrates.

The atmosphere wasn’t strong enough to contain more oxygen when compared earths atmosphere today, the exosphere was full of rips and couldn’t contain enough oxygen to provide for land creatures, although aquatic earthlings could continue i exist in this environment