Panspermia

Panspermia refers to the hypothesis that life exists throughout the Universe, distributed by meteoroids, asteroids and other spatial bodies.

Examples

 * In Prey earth was seeded by an alien races known as the Keepers to be harvested at a later time.
 * In Spore this is how life makes its way from world to world, the played of the game begins as life from within an meteorite.
 * In Star Trek the primordial oceans of several worlds through the Milky Way Galaxy (possibly even going as far as the Andromeda Galaxy as shown by the Kelvan) where seeded by the Ancient Humanoid.