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Question

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

Match each lower invertebrate representative organism on the left with its corresponding defining anatomical or physiological feature on the right.

  • SpongillaChoanocytes (collar cells) lining inner chambers for filter feeding
  • ObeliaMetagenesis involving alternating sessile polyp and motile medusa forms
  • PlanariaFlame cells (protonephridia) specialized for osmoregulation and excretion
  • AscarisPseudocoelomate body cavity enclosed by a tough, flexible cuticle

Answer

Spongilla matches with Choanocytes lining inner chambers for filter feeding; Obelia matches with Metagenesis involving alternating sessile polyp and motile medusa forms; Planaria matches with Flame cells specialized for osmoregulation and excretion; Ascaris matches with Pseudocoelomate body cavity enclosed by a tough, flexible cuticle.
Each genus represents a specific lower invertebrate phylum defined by key diagnostic traits: Spongilla (Porifera) uses choanocytes for filter feeding, Obelia (Coelenterata) exhibits metagenesis between polyp and medusa generations, Planaria (Platyhelminthes) uses flame cells for excretion and osmoregulation, and Ascaris (Nematoda) features a protective cuticle surrounding a pseudocoelom.

Step-by-Step Solution

1
Determine the taxonomic phylum for each representative genus
Spongilla belongs to Porifera; Obelia belongs to Coelenterata (Cnidaria); Planaria belongs to Platyhelminthes; Ascaris belongs to Nematoda.
Assigning each genus to its proper phylum clarifies its baseline anatomical organization.
2
Associate cellular, histological, and body cavity specializations with each phylum
Poriferans feature cellular-level filter-feeding choanocytes; Cnidarians display tissue-level polymorphism and metagenesis; Platyhelminthes utilize protonephridial flame cells; Nematodes possess a pseudocoelom and cuticle.
These diagnostic structures distinguish the evolutionary complexity among lower invertebrates.
3
Pair each organism with its specific diagnostic characteristic
Spongilla links to choanocytes, Obelia links to metagenesis, Planaria links to flame cells, and Ascaris links to pseudocoelom/cuticle.
Each match correctly aligns the representative organism with its phylum's key evolutionary hallmark.

Key Concept

Diagnostic anatomical structures and tissue organization across lower invertebrate phyla (Porifera, Coelenterata, Platyhelminthes, and Nematoda)
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Topics

Lower Invertebrates: Porifera, Coelenterata, Platyhelminthes, and Nematoda