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Question

Difficulty: MediumLower Invertebrates: Porifera, Coelenterata, Platyhelminthes, and Nematoda

Match each lower invertebrate organism on the left with its primary diagnostic anatomical feature on the right.

  • SyconPorous cellular body wall lined internally with collar cells (choanocytes)
  • ObeliaAlternation of generations between sessile polyp and motile medusa forms
  • PlanariaDorsoventrally flattened acoelomate body with specialized flame cells
  • AncylostomaUnsegmented cylindrical body containing a fluid-filled pseudocoelom and complete gut

Answer

Sycon matches the porous cellular body wall lined with collar cells (choanocytes); Obelia matches the alternation of generations between polyp and medusa forms; Planaria matches the dorsoventrally flattened acoelomate body with flame cells; Ancylostoma matches the unsegmented cylindrical body with a pseudocoelom and complete gut.
Sycon (Porifera) is characterized by choanocytes; Obelia (Coelenterata) exhibits alternation of polyp and medusa forms; Planaria (Platyhelminthes) possesses flame cells within a flattened acoelomate body; and Ancylostoma (Nematoda) exhibits a pseudocoelomate cylindrical body with a complete gut from mouth to anus.

Step-by-Step Solution

1
Identify the phylum classification for each listed organism.
Sycon is a sponge (Porifera); Obelia is a hydrozoan (Coelenterata); Planaria is a flatworm (Platyhelminthes); Ancylostoma is a roundworm (Nematoda).
Determining the taxonomic phylum allows direct recall of diagnostic morphological traits.
2
Match each phylum to its unique anatomical organization.
Porifera key feature: choanocytes; Coelenterata key feature: metagenesis (polyp/medusa); Platyhelminthes key feature: acoelomate/flame cells; Nematoda key feature: pseudocoelom/complete digestive tract.
Diagnostic structures define evolutionary relationships and body plan complexity across lower invertebrate phyla.

Key Concept

Diagnostic anatomical structures and developmental characteristics across lower invertebrate phyla (Porifera, Coelenterata, Platyhelminthes, and Nematoda).
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Topics

Lower Invertebrates: Porifera, Coelenterata, Platyhelminthes, and Nematoda