Question

How do most insects respire?

• A. Through skin
• B. Through gills
• C. By lungs
• D. By tracheal system

Hint:

Think of the small pores called spiracles on an insect's body and where the air goes after entering them.

Answer 1

The Correct Option is D

Step 1: Understanding the Question.
The question asks about the main way insects take in oxygen and release carbon dioxide.

Step 2: Key Concept.
Insects have a network of small air tubes called tracheae running through their body. These tracheae open to the outside through small pores on the body wall called spiracles, and they branch into finer tracheoles that reach almost every tissue and deliver oxygen straight to the cells.

Step 3: Detailed Explanation.
Respiration through skin is mainly seen in animals such as earthworms and amphibians, where a thin, moist skin allows gases to pass through by diffusion. Most insects have a hard, waterproof outer cuticle that blocks this kind of exchange.
Gills are used by aquatic animals such as fish and by the young stages of a few aquatic insects, but they are not the general breathing organ for insects as a group.
Lungs are the breathing organs of many vertebrates, including reptiles, birds and mammals. Insects do not have lungs.
The tracheal system is the actual breathing system of insects. Air enters through spiracles, moves through the tracheae, and reaches individual cells through fine tracheoles, so oxygen gets delivered without needing to be carried by blood.

Step 4: Final Answer.
Most insects respire by the tracheal system.