Which one of the following organisms primarily utilizes cutaneous respiration (breathing through skin)?

Correct Option

The correct option is

Earthworm

Explanation

Respiration involves the exchange of gases (oxygen and carbon dioxide) between an organism and its environment. Different animal groups have evolved specific respiratory organs based on their habitat and level of organization. Cutaneous respiration refers to the process where gas exchange occurs directly through the moist surface of the skin.

Option Analysis

• Cockroach: Incorrect. Insects like cockroaches respire through a network of tubes called the tracheal system. Air enters through small openings on the body surface called spiracles, not through the skin itself for direct diffusion into the blood.
• Earthworm: Correct. Earthworms lack specialized respiratory organs like lungs or gills. They utilize their moist, vascularized cuticle (skin) for gas exchange. Oxygen dissolves in the moisture on the skin and diffuses into the blood capillaries, while carbon dioxide diffuses out.
• Fish: Incorrect. Most fish respire through specialized vascularized structures called gills (branchial respiration), which extract dissolved oxygen from water.
• Lizard: Incorrect. Lizards are reptiles, which are terrestrial vertebrates. They respire primarily through lungs (pulmonary respiration).

Key Takeaway

Earthworms rely entirely on cutaneous respiration, requiring their skin to remain moist to facilitate the diffusion of gases, whereas insects use tracheal systems, fish use gills, and reptiles use lungs.