What is the role of unicellular organisms in nature

In nature, free-living unicellulars perform diverse roles. There are unicellular ones that carry out photosynthesis – autotrophs (green algae), there are herbivorous – phytotrophs (feed on algae), there are predators and parasites – heterotrophs (feed on other unicellular or small multicellular organisms), and there are saprotrophs (feed on dead plant or animal material).
In unicellular organisms, metabolic processes proceed relatively quickly; therefore, they make a great contribution to the cycle of substances in biogeocenosis, especially to the carbon cycle. In addition, unicellular animals (protozoa), swallowing and digesting bacteria (i.e., primary destructors), accelerate the process of updating the composition of the bacterial population. Herbivorous and predatory organisms also fulfill their function in the ecosystem, directly participating in the breakdown of plant and animal material.

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