Why are fatty acids better than glycogen for storing large amounts of chemical energy?

The fatty acids or fats provide a large amount of energy about 9 kcal g⁻¹ than glycogen which provides about t 4 kcal g⁻¹.

This large difference in the calorific value is due to the nature of the fatty acids as these are much more reduced than the glycogen as well as they are stored in the body in anhydrous form due to non-polar triacylglycerols in the adipose cells. The carbohydrates are highly hydrated compounds as they contain polar molecules in their structure which binds the water molecules.

So, the evolution selected the fatty acids over glycogen for the production of the chemical energy.

small, big, or no change could occur in the phenotype. it could cause something as simple as a cats ears to curl backwards or something as frighting as death. it could also occur in the protien-coding area and have an effect on that but no effect on the amino acids. what has to occur is a changing in the hox gene or the control gene.