Examkin

Question

Difficulty: Very hardExcretion and Excretory Organs

An investigation into the excretory mechanisms of four diverse invertebrate species revealed distinct structures for nitrogenous waste elimination:
- Structure P: Uses ciliated flame cells to propel fluid through a network of branching tubules.
- Structure Q: Relies on ciliated funnels (nephrostomes) opening into the coelom for fluid filtration and tubular reabsorption.
- Structure R: Consists of blind-ending tubules lying free in the hemolymph that actively transport nitrogenous wastes as uric acid into the hindgut.
- Structure S: Relies entirely on simple diffusion across the general body wall without specialized excretory organs.

Which of the following correctly matches excretory structures P, Q, R, and S with their respective animal representatives?

  1. P: Planaria, Q: Earthworm, R: Cockroach, S: HydraAnswer
  2. B
    P: Earthworm, Q: Planaria, R: Cockroach, S: Hydra
  3. C
    P: Planaria, Q: Cockroach, R: Earthworm, S: Hydra
  4. D
    P: Hydra, Q: Earthworm, R: Planaria, S: Cockroach

Answer

Structure P is found in Planaria, Structure Q in Earthworm, Structure R in Cockroach, and Structure S in Hydra.
The correct alignment pairs Planaria with flame cells (protonephridia), Earthworm with ciliated nephridial funnels (metanephridia), Cockroach with Malpighian tubules eliminating uric acid via hemolymph, and Hydra with unspecialized body surface diffusion.

Step-by-Step Solution

1
Identify Structure P
Flame cells (protonephridia) with beating cilia are specialized excretory units characteristic of Platyhelminthes (e.g., Planaria).
Flame cells maintain osmoregulation and excretion by driving fluid through excretory canals.
2
Identify Structure Q
Nephridia (metanephridia) with ciliated funnels collecting coelomic fluid belong to Annelida (e.g., Earthworm).
Coelomic fluid enters the nephrostome and undergoes selective reabsorption along the nephridial tubule.
3
Identify Structure R
Malpighian tubules floating in hemolymph and excreting solid uric acid into the digestive tract are unique to terrestrial Arthropoda, specifically Insecta (e.g., Cockroach).
This adaptation conserves water by converting waste into insoluble uric acid.
4
Identify Structure S
Absence of specialized excretory organs, relying on direct diffusion of ammonia across body layers, is characteristic of simple diploblastic organisms like Cnidaria (e.g., Hydra).
High surface-area-to-volume ratio in thin body walls allows direct diffusion into the aquatic environment.

Key Concept

Invertebrate Excretory Structures and Evolutionary Adaptations
Estimated Time:2m 0s
Rate this question

Topics

Excretion and Excretory Organs

More questions from this topic