The correct statement about respiration are
(i) In cockroach gaseous exchange occurs mainly between tracheoles and haemolymph
(ii) increase in inspiratory capacity does not involve an increase in tidal volume
(iii) partial pressure of oxygen in blood is less than that in alveoli
(iv) chloride shift in erythrocytes maintain the ionic balance

Options

A. I and ii
B. I iii and iv
C. I ii andiv
D. ii and iii

Answer

To determine the correct statements about respiration, let's analyze each statement one by one.

### Step 1: Analyze Statement (i)
**Statement:** In cockroach, gaseous exchange occurs mainly between tracheoles and haemolymph.

- In cockroaches, the respiratory system consists of a network of tubes called tracheae that branch into smaller tubes known as tracheoles.
- Gaseous exchange occurs primarily at the level of the tracheoles, which are in direct contact with the tissues of the cockroach.
- The tracheoles deliver oxygen directly to the tissues and remove carbon dioxide, which is then transported back through the tracheae to the outside.
- The hemolymph (the fluid equivalent to blood in insects) bathes the tissues but does not directly participate in gas exchange; it is the tracheoles that facilitate this exchange.

**Conclusion:** This statement is **incorrect** because gaseous exchange occurs between tracheoles and tissues, not primarily with hemolymph.

### Step 2: Analyze Statement (ii)
**Statement:** Increase in inspiratory capacity does not involve an increase in tidal volume.

- Inspiratory capacity is defined as the maximum amount of air that can be inhaled after a normal expiration, which is the sum of tidal volume (the amount of air inhaled or exhaled in a normal breath) and inspiratory reserve volume (the additional air that can be inhaled after a normal inhalation).
- If inspiratory capacity increases, it implies that either tidal volume, inspiratory reserve volume, or both must increase.

**Conclusion:** This statement is **incorrect** because an increase in inspiratory capacity must involve an increase in either tidal volume or inspiratory reserve volume.

### Step 3: Analyze Statement (iii)
**Statement:** Partial pressure of oxygen in blood is less than that in alveoli.

- The partial pressure of oxygen (PO2) in the alveoli is typically around 104 mm Hg, while the PO2 in venous blood (deoxygenated) is about 40 mm Hg and in arterial blood (oxygenated) it is around 95 mm Hg.
- This indicates that the PO2 in blood is indeed less than that in the alveoli, which is essential for the diffusion of oxygen from the alveoli into the blood.

**Conclusion:** This statement is **correct**.

### Step 4: Analyze Statement (iv)
**Statement:** Chloride shift in erythrocytes maintains the ionic balance.

- The chloride shift refers to the process where bicarbonate ions (HCO3-) move out of red blood cells (RBCs) into the plasma, and chloride ions (Cl-) move into the RBCs to maintain electrical neutrality.
- This process is crucial for the transport of carbon dioxide in the blood, as most CO2 is converted to bicarbonate in the RBCs.

**Conclusion:** This statement is **correct**.

### Final Conclusion
The correct statements about respiration are:
- (iii) Partial pressure of oxygen in blood is less than that in alveoli.
- (iv) Chloride shift in erythrocytes maintains the ionic balance.

Thus, the correct answers are **(iii) and (iv)**.

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