Because of the similarity of these organelles to prokaryotic cells, the endosymbiotic model proposes that they arose from small prokaryotes that established residence inside larger ones, deriving their outer membranes from the plasma membrane of the host cell. Mitochondria arose from small heterotrophic prokaryotes that had great efficiency in aerobic respiration, and chloroplasts arose from small photosynthetic autotrophs. Because the organelles could not be digested, they eventually evolved to assume a closely interdependent relationship with the cell, and today could not even survive on their own. There is truly immense diversity within the Domain Eukarya. It includes the kingdoms Protista , Fungi , Plantae , and Animalia .
Fungi are chemoheterotrophic, mostly multicellular decomposers with a unique reproductive cycle.
Finally, Animalia are multicellular chemoheterotrophs with a simple life cycle and no cell walls.