Cockroach has no R.B.C. but respires due to :

Options

A. Gaseous exchange takes place directly through tissues
B. Haemoglobin combines with oxygen
C. Oxygen is taken by lungs
D. Oxygen is taken by book lungs

Answer

To answer the question "Cockroach has no R.B.C. but respires due to:", we need to understand the respiratory system of the cockroach and how it functions without red blood cells (RBCs). Here’s a step-by-step breakdown of the solution:

### Step-by-Step Solution:

1. **Understanding the Circulatory System of Cockroach**:
- Cockroaches have an open type of circulatory system. This means that their blood, known as hemolymph, flows freely within the body cavity (hemocoel) rather than being confined to blood vessels.

**Hint**: Remember the difference between open and closed circulatory systems.

2. **Composition of Cockroach Blood**:
- The blood of a cockroach is called hemolymph, which is not red because it does not contain red blood cells (RBCs) or hemoglobin. Therefore, it does not transport oxygen in the same way that vertebrate blood does.

**Hint**: Consider why the color of blood is important for its function.

3. **Gaseous Exchange Mechanism**:
- Instead of using hemoglobin to carry oxygen, cockroaches have a specialized system for respiration. They utilize a network of tubes called trachea, which are responsible for gas exchange.

**Hint**: Think about how insects might have adapted their respiratory systems differently from mammals.

4. **Structure of Trachea**:
- The tracheal system consists of six longitudinal tracheal tubes (two dorsal, two ventral, and two lateral) that are interconnected by transverse commissures. This network allows for efficient transport of gases.

**Hint**: Visualize the tracheal system as a branching network that delivers air directly to tissues.

5. **Role of Spiracles**:
- The atmospheric air enters and exits the cockroach's body through small openings called spiracles. There are ten pairs of spiracles that facilitate the diffusion of air in and out of the body.

**Hint**: Consider how the location and structure of spiracles might affect gas exchange.

6. **Direct Gas Exchange**:
- The gaseous exchange occurs directly at the tissue level. Oxygen diffuses directly from the trachea into the tissues, and carbon dioxide diffuses back into the trachea to be expelled.

**Hint**: Reflect on how this direct exchange might be more efficient for small organisms like cockroaches.

### Conclusion:
The correct answer to the question is that cockroaches respire due to the direct exchange of gases through their tracheal system, which allows oxygen to reach tissues without the need for red blood cells.

### Final Answer:
Cockroach has no R.B.C. but respires due to direct gaseous exchange through the tracheal system.