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Difficulty: HardMorphological and Physiological Adaptations to Environments

Marine elasmobranchs, such as sharks, maintain hyperosmotic body fluids relative to seawater primarily by retaining high concentrations of urea and trimethylamine oxide (TMAO) in their blood plasma, allowing water to enter passively across their gills without the need to drink seawater.

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Answer

The statement is True. Marine elasmobranchs accumulate urea and TMAO in their blood to stay hyperosmotic to seawater, gaining water passively via osmosis.
The statement correctly details how marine cartilaginous fishes solve osmotic stress. By accumulating urea and TMAO in their blood plasma, their body fluids become hyperosmotic to seawater, drawing water inward passively through osmotic pressure.

Step-by-Step Solution

1
Identify the organism group and habitat
Marine elasmobranchs (cartilaginous fishes like sharks and rays) inhabiting high-salinity aquatic environments.
Environmental salinity dictates the osmotic gradient and necessary physiological adjustments for water balance.
2
Analyze the osmoregulatory mechanism
Elasmobranchs retain metabolic urea and TMAO in blood plasma instead of excreting them immediately.
High solute concentrations raise internal osmotic pressure above that of seawater (hyperosmolality).
3
Determine the direction of water movement and evaluation
Water continuously diffuses into the fish passively across the gills, making active drinking unnecessary.
This confirms that the statement accurately describes physiological adaptation in elasmobranchs.

Key Concept

Physiological Osmoregulation in Marine Elasmobranchs
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Topics

Morphological and Physiological Adaptations to Environments

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