Final answer:
Foraminiferans are unicellular protists that form shells made of calcium carbonate, essential for marine environments.
Explanation:
Foraminiferans, also known as forams, are unicellular heterotrophic protists that produce shells made of various organic materials, typically hardened with calcium carbonate. These organisms range in size and play a vital role in marine environments, with their pseudopodia aiding in movement and feeding.
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