Flexi Says: Most eukaryotes have mitochondria, while every multi-cellular eukaryote does. However, a few one-celled eukaryotes lack mitochondria. All of this type of eukaryote live as parasites. Additionally, some multicellular eukaryotes lack mitochondria in specific cells. For example, human red blood cells lack mitochondria, an adaptation that either reduces the cells' size or prevents them from using the oxygen they carry.
