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

Match each lower invertebrate representative on the left with its characteristic anatomical or diagnostic feature on the right.

  • Sponges (Porifera)Body perforated by pores (ostia) and lined with choanocytes
  • Hydra (Coelenterata)Tentacles armed with stinging cells (nematocysts)
  • Planaria (Platyhelminthes)Excretory system composed of specialized flame cells
  • Ascaris (Nematoda)Unsegmented cylindrical body with a pseudocoelom

Answer

Sponges correspond to 'Body perforated by pores (ostia) and lined with choanocytes'; Hydra corresponds to 'Tentacles armed with stinging cells (nematocysts)'; Planaria corresponds to 'Excretory system composed of specialized flame cells'; Ascaris corresponds to 'Unsegmented cylindrical body with a pseudocoelom'.
Each lower invertebrate group exhibits a unique evolutionary structure: Porifera (Sponges) feature porous bodies lined with choanocytes; Coelenterata (Hydra) feature nematocysts on tentacles; Platyhelminthes (Planaria) utilize flame cells for waste regulation; and Nematoda (Ascaris) possess a cylindrical body with a pseudocoelom.

Step-by-Step Solution

1
Identify the key structural features associated with Phylum Porifera.
Sponges possess ostia and choanocytes (collar cells).
Porifera organisms rely on cellular-level organization with flagellated cells to drive water through ostia.
2
Identify the diagnostic structures of Phylum Coelenterata (Cnidaria).
Hydra possesses nematocysts on its tentacles.
Coelenterates are diploblastic organisms characterized by stinging organelles for defense and food capture.
3
Identify the excretory structures unique to Phylum Platyhelminthes.
Planaria uses flame cells for excretion.
Flatworms lack a circulatory system and rely on specialized ciliated flame cells (protonephridia) to eliminate fluid waste.
4
Identify the body cavity arrangement characteristic of Phylum Nematoda.
Ascaris has an unsegmented cylindrical body with a pseudocoelom.
Nematodes are roundworms with a complete digestive tract supported by a pseudocoelomic cavity.

Key Concept

Diagnostic structural features and body organization of lower invertebrate phyla
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Topics

Lower Invertebrates: Porifera, Coelenterata, Platyhelminthes, and Nematoda