Any of numerous chiefly marine invertebrates typically having a soft, unsegmented body, a mantle, and a protective calcareous shell are categorized as?

The correct categorization of these organisms as mollusks is based on their defining characteristics, which include a soft, unsegmented body and a mantle. The mantle is a significant feature in mollusks, as it covers the body organs and often produces the calcareous shell that many of these invertebrates have.

Mollusks represent a diverse group of animals that inhabit a range of environments, mostly in marine settings. They include well-known species such as snails, clams, and octopuses. The presence of a protective shell serves a vital role in their survival, providing defense against predators and harsh environmental conditions.

In contrast, echinoderms like starfish and sea urchins have a distinct internal skeleton made up of calcareous plates, and their body structure is quite different from that of mollusks. Sponges are simple, multicellular organisms that lack true tissues and organs, featuring a porous body rather than the unsegmented form typical of mollusks. Crustaceans, which include crabs and lobsters, are characterized by a hard exoskeleton and segmented body structure, setting them apart from the unsegmented bodies of mollusks. Hence, the defining traits of moll