Which group includes organisms characterized by soft bodies and often a hard shell?

The group that includes organisms characterized by soft bodies and often a hard shell is Mollusca. This diverse phylum encompasses a wide variety of animals, such as snails, clams, and octopuses. Mollusks typically have a soft, unsegmented body divided into three main parts: the foot, the visceral mass, and the mantle. The mantle secretes the hard shell, which serves as protection and support for many mollusks, particularly in marine and freshwater environments.

Mollusks are known for their unique body plan and significant ecological roles, including their contribution to nutrient cycling and serving as food sources for various predators. Their adaptability allows them to inhabit a range of environments, from deep oceans to freshwater rivers and lakes. The presence of a hard shell in many members of this phylum is a distinguishing feature that protects them from environmental threats and predation.

Understanding the characteristics of Mollusca is essential in taxonomic certification, as it highlights the diversity and ecological significance of these organisms within freshwater ecosystems.