I think it’s organism since it already stated skeletal and respiratory then it means it cannot be tissue or organ because skeletal is included so i say go for organism
By consuming less than 1200 calories a day it impacts a person’s metabolism by slowing it down and forcing the body to break down its own tissues if it is not receiving sufficient calories to withstand vital functions. There are slight side effects of a less than 1200 calories which are faintness, tiredness, irregular periods, and unsteadiness. Some major side effects might have impact on the gallbladder, gout, excruciating inflammation of the joints and also death.
90% of the available energy is lost in some form of heat, transferring light energy into different living organisms
