Spores are tiny structures used by organisms to disperse into new environments, to survive temporarily unfavorable conditions, or to undergo sexual reproduction.

In zoology, spores are asexual, resting bodies, which depending on the species can be one-celled or multi-cellular. Many protozoans have a life-cycle stage involving the development of a spore (or cyst) that is capable of surviving drought or other extreme environmental conditions. Most parasitic species, for example, must survive extremely inhospitable conditions during transmission from host to host, which often occurs through the ambient environment. Free-living protozoans also commonly utilize a spore stage to survive periods of severe environmental stress, as might occur when a pond becomes dry in late summer, or freezes during winter.

Many kinds of bacteria, fungi, actinomycetes, yeasts, and algae also develop spores, allowing them to survive periods of unfavorable conditions. Most species of fungus also develop spores as part of their...