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Any of about 500 species of primitive organisms that contain true nuclei and resemble both protists and fungi (seefungus). Originally grouped within the kingdom Fungi, some classification systems consider slime molds to be in the kingdom Protista. They typically thrive in dark, cool, moist conditions such as on forest floors. Bacteria, yeast, molds, and fungi provide the main source of slime-mold nutrition. The complex life cycle of slime molds, exhibiting complete alternation of generations, may clarify the early evolution of both plant and animal cells. In the presence of water a tiny spore releases a mass of cytoplasm called a swarm cell, which later develops into an amoebalike creeping cell called a myxamoeba. Both swarm cells and myxamoebas can fuse in sexual union; the resulting fertilized cell, or plasmodium, grows through nuclear division and forms a spore case, which, when it dries, disintegrates and releases spores to begin the cycle again.
This entry comes from Encyclopædia Britannica Concise. For the full entry on slime mold, visit Britannica.com.