Which of the following statements is/are correct ?
1. Dolphins and Whales breathe through blowholes.
2. Earthworm breathe through their skin.
Select the correct answer from the code given below :

Question

UnlockIAS · Accepted Answer

Correct — B, Both 1 and 2. Statement 1 is true: dolphins and whales are cetaceans — aquatic mammals, not fish — and they breathe atmospheric air using lungs. Over evolutionary time their nostrils migrated from the tip of the snout to the top of the head, forming the blowhole, so the animal can exhale and inhale by breaking the surface with only the crown of its head. A muscular flap seals the blowhole while the animal is submerged. Statement 2 is also true: the earthworm has no lungs, no gills and no tracheae. It respires cutaneously — oxygen dissolves in the film of moisture on its body surface and diffuses through the thin, permeable skin into a dense network of capillaries lying just beneath, where the respiratory pigment carried in the blood transports it onward. That is precisely why an earthworm must keep its skin moist, and why it comes to the surface when the soil is waterlogged. Both statements stand, so the key marks (b).

Why the other options are wrong — (a) It accepts the earthworm but rejects the blowhole. That usually comes from treating whales and dolphins as fish. They are mammals — warm-blooded, giving birth to live young and suckling them — and they never developed gills; they must surface to breathe through the blowhole, which is why a drowning cetacean is a real danger.  (c) Both statements are in fact correct, so rejecting both is doubly wrong. The blowhole is the standard textbook example of a nostril relocated for surface breathing, and cutaneous respiration in the earthworm is the standard example of gas exchange without any specialised respiratory organ.  (d) It accepts the blowhole but denies that earthworms breathe through the skin. The earthworm has no specialised respiratory organ at all — no lungs, gills or tracheal tubes — so the moist body wall is its only gas-exchange surface. This is the option chosen by candidates who assume every animal must possess a dedicated breathing organ.

Concept: Animals exchange gases in ways that follow their body plan, not simply their habitat. Very small or thin-bodied animals such as the earthworm rely on plain diffusion across the moist general body surface (cutaneous respiration). Insects run air directly to the tissues through a branching tracheal system opening at spiracles. Fish and most aquatic larvae use gills. Terrestrial vertebrates — and air-breathing aquatic mammals like whales and dolphins — use lungs. Cetaceans are the clearest proof that ancestry beats habitat: they returned to the sea but kept mammalian lungs, and simply moved the nostril to the top of the head.

State PCS 2025 Q66 — Science & Technology PYQ with Answer

State PCS 2025 Q66 — Science & Technology PYQ with Answer