Symbiogenesis, or endosymbiotic theory, is an evolutionary theory that explains the origin of eukaryotic cells from prokaryotes.It states that several key organelles of eukaryotes originated as a symbiosis between separate single-celled organisms.he theory of symbiogenesis (Greek: ÏÏÎ½ syn together, Î²Î¯ÏÏÎ¹Ï biosis living, and Î³Î­Î½ÎµÏÎ¹Ï genesis origin or birth) theory were first articulated by the Russian botanist Konstantin Mereschowsky in 1910, although he described the fundamental elements of the theory were described in a paper five years earlier.
Definition of rider: Additional clause, document, or slip of paper that adds, alters, amends, or removes the provisions of an associated or attached agreement or contract (such as an insurance policy) or a negotiable ...
n., pl. horsâ¢es, (esp. collectively) horse, n. 1. a large, solid-hoofed, herbivorous mammal, Equus caballus, domesticated since prehistoric times, bred in numerous varieties, and used for carrying or pulling loads and for riding. 2. a fully mature male animal of this type; stallion. 3. something on which a person rides, sits, or exercises, as if astride the back of such an animal: rocking horse. 4. Also called trestle. a frame or block, with legs, on which something is mounted or supported.