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

A soft-bodied marine organism collected during a field expedition features an unsegmented body, a muscular foot for crawling, and a specialized chitinous rasping structure called a radula. To which phylum does this specimen belong, and what is the chief role of its surrounding mantle tissue?

  1. Mollusca; secreting the protective shell and enclosing the visceral mass.Answer
  2. B
    Annelida; facilitating true metameric body segmentation and hydrostatic locomotion.
  3. C
    Arthropoda; producing a rigid jointed exoskeleton replaced by periodic molting.
  4. D
    Echinodermata; regulating fluid pressure within a hydraulic water vascular system.

Answer

Mollusca; secreting the protective shell and enclosing the visceral mass.
The correct option correctly identifies the phylum Mollusca. Members of Mollusca are characteristically soft-bodied, unsegmented invertebrates with a body plan typically divided into a head, muscular foot, and visceral mass. The mantle is a specialized epidermal layer that secretes the calcareous shell and encloses the mantle cavity. The radula is a unique chitinous rasping tongue-like structure present in most molluscs (except bivalves) for scraping food.

Step-by-Step Solution

1
Identify key diagnostic features described in the stem.
The organism has an unsegmented soft body, a muscular foot, a radula, and a mantle tissue.
These anatomical features are diagnostic hallmarks of specific higher invertebrate phyla.
2
Map the diagnostic features to the correct phylum and identify mantle function.
The radula, soft body, and mantle are characteristic of Mollusca, where the mantle secretes the calcareous shell.
No other higher invertebrate phylum possesses a radula for feeding or a mantle cavity surrounding the visceral mass.

Key Concept

Diagnostic anatomical structures of phylum Mollusca
Estimated Time:1m 0s
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Topics

Higher Invertebrates: Annelida, Mollusca, Arthropoda, and Echinodermata

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