A. to increase food production
D. functional group isomerism
I don't know if this is what you're looking for but...
examples of abiotic factors in a marine ecosystem could be the water, oxygen in the water which helps the animals in the water breathe, and the sun that reflects into the water.
Often these molecules are carbohydrates, attached to certain lipids, or also I believe are called as glycolipids. These are marker molecules and are used to distinguish cells from each other. As cells can differentiate from one another based on the composition of the carbohydrates present on the lipids, I believe.
