There is a good chance higher animals would not exist without mitochondria, according to Molecular Expressions from The Florida State University. Without these organelles, it would be very difficult for some organisms to produce enough energy to survive.
Mitochondria convert oxygen and nutrients into a form of energy called adenosine triphosphate, or ATP. Cells need ATP to perform all of their metabolic functions. Researchers from The Florida State University say cells are able to produce approximately 15 times more energy with mitochondria than they would without it.
If cells did not have any mitochondria, they would have to use anaerobic glycolysis to produce ATP, according to the fourth edition of "Molecular Biology of the Cell." This process converts glucose into a substance called pyruvate, but it is less efficient than aerobic respiration so only a small amount of the energy from glucose is released. When pyruvate enters the mitochondria, however, the sugars are completely metabolized. As a result, more energy is available to the cell.
Humans also need mitochondria to produce cholesterol and a component of hemoglobin, notes Genetics Home Reference. Even if cells were able to produce enough energy using anaerobic glycolysis, it is likely humans would still not be able to survive without mitochondria to help regulate these functions.