Respiratory System — Biology

Q.1

WBCS Prelims 2018

Which one of the following organs is the main respiratory organ of whale?

A. Integuments

B. Gills

C. Lungs

D. Trachea

Explanation

Why Correct: Whales are marine mammals that breathe atmospheric air using lungs, surfacing regularly through blowholes evolved from nostrils.
Distractor Analysis: Integuments refer to skin and cannot serve as primary respiratory organs in whales. Gills are respiratory structures of fish and aquatic invertebrates, not mammals. Trachea is the windpipe that conducts air to lungs but not the main gas exchange site.
Takeaway: Cetacean lungs feature reinforced airways and high myoglobin concentrations allowing prolonged dives, with sperm whales capable of 90-minute breath-holds.

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Q.2

WBCS Prelims 2013

Portion of the carapace which covers the gill of prawn is known as —

A. Bronchus

B. Branchiostegal membrane

C. Branchiostegite

D. Branchiostegal spine

Explanation

Why Correct: Branchiostegite is the lateral extension of the carapace that forms the gill cover in crustaceans like prawns, enclosing the branchial chamber.
Distractor Analysis: Bronchus refers to air passages in mammalian lungs. Branchiostegal membrane is a thin membrane in fish that supports gill filaments. Branchiostegal spine is a bony element in fish that supports the branchiostegal membrane.
Takeaway: In crustacean anatomy, the carapace covers the cephalothorax dorsally, while branchiostegites protect gills laterally.

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Q.3

WBPSC Miscellaneous Prelims 2009

Tracheal Gill is found in

A. Limulus or King crab

B. Mosquito Larva

C. Fish

D. Salamander

Explanation

Why Correct: Tracheal gills are respiratory structures found in some aquatic insect larvae, including mosquito larvae, where they allow gas exchange from water through thin-walled outgrowths containing tracheae.
Distractor Analysis: Limulus (horseshoe crab) has book gills, not tracheal gills. Fish possess gill slits with gill filaments, not tracheal gills. Salamander larvae have external gills, which are not tracheal.
Takeaway: Tracheal gills are characteristic of certain insect larvae (e.g., mayflies, caddisflies, and mosquitoes) and are distinct from gills of fish or amphibians.

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Q.4

WBPSC Miscellaneous Prelims 2007

Respiratory organ of whale is

A. Gills

B. Lungs

C. Both lungs and gills

D. Air sacs

Explanation

Why Correct: Whales are marine mammals and breathe air through lungs; they must surface to inhale and exhale.
Distractor Analysis: Gills are present in fish and aquatic arthropods; air sacs are found in birds; whales do not have both respiratory systems.
Takeaway: All mammals, including fully aquatic ones like whales and dolphins, possess lungs as the primary respiratory organ.

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