Biology Homeostasis PMDC Conceptual Practice
PMDC Verified Question 20 of 99
Freshwater protozoans eliminate excess water entering continuously by osmosis using specialized organelles called:
A
Flame cells
B
Contractile vacuoles
C
Malpighian tubules
D
Nephridia
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Contractile vacuoles
Concept: Subcellular osmoregulation in unicellular protists.

Solution: Freshwater unicellular organisms (e.g., Amoeba, Paramecium) collect cytosolic water into a contractile vacuole, which periodically fuses with the plasma membrane to pump water out.

Why other options are incorrect:
  • Option A: Flame cells are multicellular excretory structures in flatworms (Planaria).

  • Option C: Malpighian tubules are excretory organs in insects.

  • Option D: Nephridia are excretory organs in annelids.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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