Although not every species in existence has been specifically studied for sleep patterns, scientists generally agree that all organisms need to sleep in some fashion. Sleep patterns differ from species to species, though, making a definitive answer next to impossible.
Human beings, for example, generally sleep for hours at a time, while other species, like the giraffe, only sleep for about 30 minutes per day. Brown bats, on the other hand, can sleep for up to 20 hours per day. Some animals can alter their sleep patterns when necessary, while others practice unihemispheric sleep, a process that allows one half of the animal's brain to sleep while the other half remains alert.