Kingdom Protista includes mostly unicellular, eukaryotic life forms that behave similar to animals, plants and fungi based upon how the organisms obtain nutrition from their environment. These creatures do not fit into other kingdoms of life, mostly live in water and have a nucleus in their cells.
Animal-like protists are called protozoa. These organisms include amoebas, plasmodia and paramecia. Protozoans feed by absorbing nutrition through membranes, surrounding and engulfing food sources, engaging in parasitism or eat through a small mouth pore. These creatures move using flagella, cilia or pseudopods.
Plant-like protists include green algae, red algae, brown algae, plankton, kelp and sea lettuce, which all get their nutrition from photosynthesis. Many of these organisms are multi-cellular colonists that grow in freshwater or saltwater environments. Colonizing means life forms bunch together to form huge clusters that can overwhelm some ecosystems.
Fungi-like protists, or myxomycota, are colloquially called slime molds. These creatures absorb nutrition from their surrounding environments and move like amoebas. Entire masses of myxomycota inhabit rotting wood in forests and exist as a clump of cytoplasm.
Protists reproduce sexually, asexually, through fission or simply by multiplying. Individual protists are small and can be observed under a microscope. More than 30,000 different species exist around the planet.