The evolution of the mitochondrion enabled multicellularity and diversity of life histories that necessitated not merely a large, but in many cases, a variable supply of energy. With that, individual organisms also need a means to precisely regulate energy to match life’s demands. Over the past 15 years, a growing number of researchers have delved into evaluating mitochondrial respiratory function to understand evolutionary adaption and constraints on energetic capacity. Within these data, we have seen many examples suggesting that the energetic capacity of mitochondria is not fixed within individuals and can vary with genotype, leakiness of the mitochondria’s inner membrane, and oxidative damage. Yet, these do not appear to be the only means by which animals can adjust their capacity for oxidative phosphorylation. With this presentation, I will review evidence from my lab and others suggesting that changes in mitochondrial morphology and mitochondrial dynamics (most notably fission and fusion) play an essential role in up and down-regulating oxidative phosphorylation and mitigating oxidative damage. I will propose that these processes are vital to the diversity of energetic ability observed throughout Animalia.