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

Which of the following developmental features provides strong evidence of a close evolutionary relationship between the phyla Annelida and Mollusca?

  1. The presence of a trochophore larval stage during early developmentAnswer
  2. B
    The presence of jointed appendages and a chitinous exoskeleton
  3. C
    The excretion of metabolic waste solely through Malpighian tubules
  4. D
    The development of a water vascular system for locomotion

Answer

The presence of a trochophore larval stage during early development
Both Annelida and Mollusca exhibit a trochophore larva during their embryonic development. This shared larval stage is a key ancestral characteristic demonstrating evolutionary affinity between these two higher invertebrate phyla.

Step-by-Step Solution

1
Identify the shared developmental characteristics among higher invertebrate phyla
Annelida and Mollusca both belong to the Lophotrochozoa clade and produce a distinct ciliated larval form called a trochophore.
Larval morphology often preserves ancestral evolutionary lineages that adult structures may conceal.
2
Evaluate alternative phyla characteristics to eliminate incorrect options
Jointed appendages belong to Arthropoda, Malpighian tubules belong to terrestrial arthropods, and the water vascular system belongs to Echinodermata.
Distinguishing diagnostic phylum-specific adaptations prevents cross-phylum misattribution.

Key Concept

Evolutionary relationships and developmental stages in higher invertebrates
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Topics

Higher Invertebrates: Annelida, Mollusca, Arthropoda, and Echinodermata

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