Autotrophic does not need foreign organic matter, and can synthesize the required organic matter by itself; Heterotrophication requires external organic matter; Saprophytic enzymes: obtain nutrients from animal and plant carcasses or decaying tissues to maintain their own lives; Parasitism is the use of host nutrients to maintain their own lives; Prokaryotes have no nuclei, only pseudonuclei; Eukaryotes have nuclei.