Question

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

In lower invertebrates, metabolic waste elimination and osmotic regulation rely on distinct structural adaptations across different phyla. Match each phylum on the left with its corresponding excretory or osmoregulatory feature on the right.

  • PoriferaIntracellular diffusion via choanocyte-driven water currents through the osculum
  • CoelenterataDirect diffusion across body layers surrounding a central gastrovascular cavity
  • PlatyhelminthesNetwork of flame cells (protonephridia) functioning primarily in osmoregulation
  • NematodaRenette cells and longitudinal excretory canals in a pseudocoelomic cavity

Answer

Porifera matches intracellular diffusion via choanocyte-driven water currents through the osculum; Coelenterata matches direct diffusion across body layers surrounding a central gastrovascular cavity; Platyhelminthes matches network of flame cells (protonephridia) functioning primarily in osmoregulation; Nematoda matches renette cells and longitudinal excretory canals in a pseudocoelomic cavity.
Each lower invertebrate phylum demonstrates an evolutionary progression in waste management and fluid balance: Porifera rely on individual cell diffusion powered by choanocyte water movement; Coelenterata use direct diffusion across their two tissue layers into the gastrovascular cavity; Platyhelminthes employ flame cells within protonephridia for osmoregulation; and Nematoda utilize renette cells coupled with excretory canals housed in their pseudocoelom.

Step-by-Step Solution

1
Identify the cellular organization and water flow mechanism in Porifera.
Porifera (sponges) depend on choanocyte-maintained water currents through ostia and osculum for waste diffusion.
Sponges lack true tissues and excretory organs.
2
Determine the waste removal mechanism in diploblastic Coelenterata.
Coelenterates diffuse metabolic wastes across two cell layers into the surrounding aquatic environment or gastrovascular cavity.
They possess a tissue-level body plan with a single opening to their body cavity.
3
Recall the characteristic excretory/osmoregulatory structure of Platyhelminthes.
Flatworms rely on protonephridia with flame cells.
Flame cells maintain fluid balance and eliminate excess water and nitrogenous wastes in acoelomates.
4
Analyze the excretory system in pseudocoelomate Nematoda.
Nematodes use specialized renette cells and longitudinal excretory canals.
Roundworms have an unsegmented pseudocoelom with specialized excretory cells running along their body length.

Key Concept

Excretory and osmoregulatory mechanisms across lower invertebrate phyla
Rate this question