endosymbiont theory


endosymbiont theory

[‚en·dō′sim·bē‚änt ‚thē·ə·rē] (cell and molecular biology) A theory that the mitochondria of eukaryotes and the chloroplasts of green plants and flagellates originated as free-living prokaryotes that invaded primitive eukaryotic cells and become established as permanent symbionts in the cytoplasm.