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

A biological sample of an endoparasitic lower invertebrate reveals the presence of specialized flame cells (protonephridia) for osmoregulation and excretion, a dorsoventrally flattened triploblastic body plan, and an acoelomate internal organization. Based on these anatomical features, which phylum does this organism belong to?

  1. PlatyhelminthesAnswer
  2. B
    Nematoda
  3. C
    Coelenterata
  4. D
    Porifera

Answer

Platyhelminthes
The presence of flame cells (protonephridia), dorsoventral flattening, and a triploblastic acoelomate body design strictly characterizes members of the phylum Platyhelminthes (flatworms).

Step-by-Step Solution

1
Analyze the diagnostic excretory and anatomical structures provided in the stem.
Identified key characteristics: flame cells (protonephridia), triploblastic acoelomate body organization, and dorsoventral flattening.
Excretory structures and body cavity types are major taxometric criteria for classifying lower invertebrate phyla.
2
Match the identified diagnostic traits to the correct invertebrate phylum.
Flame cells combined with an acoelomate triploblastic structure exclusively define members of the phylum Platyhelminthes.
Nematodes possess a pseudocoelom, Coelenterates are diploblastic, and Poriferans lack distinct tissue-level organs.

Key Concept

Diagnostic anatomical structures and excretory organ mapping in lower invertebrate phyla
Estimated Time:1m 0s
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Topics

Lower Invertebrates: Porifera, Coelenterata, Platyhelminthes, and Nematoda