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Difficulty: EasyHigher Invertebrates: Annelida, Mollusca, Arthropoda, and Echinodermata

Members of a specific higher invertebrate group possess soft, unsegmented bodies that are typically protected by a hard calcareous shell secreted by a specialized muscular fold called the mantle. Which phylum exhibits these diagnostic features?

  1. MolluscaAnswer
  2. B
    Annelida
  3. C
    Arthropoda
  4. D
    Echinodermata

Answer

Mollusca is the correct phylum because its members are characterized by soft, unsegmented bodies, a mantle, and often a protective calcareous shell.
The defining diagnostic feature of Phylum Mollusca is a soft, unsegmented body typically divided into a head, muscular foot, and visceral mass, covered by a dorsal tissue fold called the mantle, which secretes a protective calcareous shell.

Step-by-Step Solution

1
Identify key diagnostic features described in the stem
The organisms are unsegmented, soft-bodied, and possess a mantle that produces a calcareous shell.
These physical features serve as fundamental criteria for distinguishing higher invertebrate phyla.
2
Match these characteristics to the appropriate invertebrate phylum
The mantle and calcareous shell uniquely define members of Phylum Mollusca.
Annelids are segmented, arthropods have jointed exoskeletons, and echinoderms have internal spiny skeletons.

Key Concept

Diagnostic characteristics of Phylum Mollusca
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Topics

Higher Invertebrates: Annelida, Mollusca, Arthropoda, and Echinodermata

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