Respiration in insects Is called direct because

Options

A. the cells exchange `O_(2)//CO_(2)` directly with the air in the tubes
B. the tissues exchange `O_(2)//CO_(2)` directly with coelomic fluid
C. the tissues exchange `O_(2)//CO_(2)` directly with the air outside thorugh body surface
D. tracheal tubes exchange `O_(2)//CO_(2)` directly with the haemocoel which then exchange with tissues.

Answer

### Step-by-Step Solution:

1. **Understanding Insect Respiration**: Insects have a unique respiratory system known as tracheal respiration. This system is different from the lungs found in many other organisms.

2. **Components of the Tracheal System**: The tracheal system consists of spiracles and tracheae. Spiracles are small openings on the body surface of the insect that allow air to enter.

3. **Air Pathway**: When an insect breathes, air enters through the spiracles. From the spiracles, the air travels into the trachea, which are tube-like structures.

4. **Tracheoles**: The trachea further branches into smaller tubes called tracheoles. These tracheoles extend throughout the insect's body and reach the individual cells.

5. **Direct Gas Exchange**: The tracheoles are in close contact with the cells, allowing for direct exchange of gases (oxygen and carbon dioxide) between the air in the tracheal system and the cells of the insect.

6. **Conclusion**: Since the exchange of gases occurs directly between the air in the tracheal tubes and the cells, respiration in insects is termed "direct respiration."

### Final Answer:
Respiration in insects is called direct because the cells exchange oxygen and carbon dioxide directly with the air in the tracheal tubes.

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