Anaerobic organisms are those that do not require oxygen for their metabolic processes. Mitochondria are organelles within eukaryotic cells that are responsible for cellular respiration, which is the process of converting oxygen and glucose into energy in the form of ATP. Since anaerobic organisms do not utilize oxygen for respiration, they do not require mitochondria for energy production. Instead, they may rely on alternative metabolic pathways, such as fermentation, to generate energy. Hence, the absence of mitochondria is expected in anaerobic organisms.