SUMMARY
Protistans are a diverse group of organisms that are found in moist or aquatic habitats. The protistans are similar in that they are eukaryotic, but they differ with regard to nutrient acquisition, reproductive strategies, and mechanisms for movement.

Although most of the protistans are unicellular microscopic organisms, they affect the macroscopic world profoundly, in both good and bad ways. For example, although they are important producers and members of the food chain, dinoflagellates, when present in large numbers, are capable of producing toxins that harm other members of the marine community (such as occurred with the manatees off the Florida Gulf Coast in 1996). Some protistans are able to cause disease in humans and other animals. Yet, overall, protistans are beneficial to the living world. Photosynthetic algae form the base of food chains in many aquatic environments, and the protozoa and slime molds play an important role in the cycling of nutrients through ecosystems.

Activity
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