Question

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

Lower invertebrates display key evolutionary innovations in their body plans, cellular organizations, and functional systems. Pair each of the following invertebrate phyla on the left with its defining structural feature on the right.

  • PoriferaPresence of flagellated choanocytes for maintaining water currents and filter feeding
  • CoelenterataSpecialized stinging organelles called nematocysts for prey capture and defense
  • PlatyhelminthesProtonephridial system containing flame cells for osmoregulation and waste excretion
  • NematodaFluid-filled pseudocoelom between mesoderm and endoderm serving as a hydrostatic skeleton

Answer

Porifera matches with presence of flagellated choanocytes; Coelenterata matches with specialized stinging nematocysts; Platyhelminthes matches with flame cells (protonephridia); Nematoda matches with fluid-filled pseudocoelom.
Each phylum is accurately matched with its primary evolutionary diagnostic feature: Porifera rely on choanocytes for feeding, Coelenterata utilize nematocysts for capture and defense, Platyhelminthes possess flame cells for osmoregulation, and Nematoda feature a pseudocoelom functioning as a hydrostatic skeleton.

Step-by-Step Solution

1
Analyze the characteristic features of Porifera
Porifera (sponges) possess specialized collar cells with flagella called choanocytes.
Choanocytes create water currents inside sponges to facilitate intracellular digestion.
2
Analyze the characteristic features of Coelenterata
Coelenterata (cnidarians) possess cnidocytes containing stinging capsules called nematocysts.
Nematocysts discharge toxins to immobilize prey and provide defense.
3
Analyze the characteristic features of Platyhelminthes
Platyhelminthes (flatworms) possess flame cells as their excretory units.
Flame cells harbor cilia that flicker like a flame to pump fluid out of the organism for osmoregulation.
4
Analyze the characteristic features of Nematoda
Nematoda (roundworms) feature an unsegmented body with a pseudocoelom.
The pseudocoelom is derived from the embryonic blastocoel and acts as a hydrostatic skeleton for movement.

Key Concept

Diagnostic anatomical structures and body cavity configurations of lower invertebrate phyla
Estimated Time:1m 30s
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