People living at sea level have- around 5 million RBC per cubic millimeter of their blood

whereas those living at an altitude of 5400 metres have around 8 million. This is because

at high altitude:

1. people get pollution-free air to breathe and more oxygen is available

2. atmospheric O₂ level is less and hence more RBCs are needed to absorb the required

amount of O₂ to survive

3. there is more UV radiation which enhances RBC production

4. people eat more nutritive food, therefore more RBCs are formed

Which one of the following statements is incorrect ?

1. The residual air in lungs slightly decreases the efficiency of respiration in mammals

2. The presence of non-respiratory air sacs, increases the efficiency of respiration in birds

3. In insects, circulating body fluids serve to distribute oxygen to tissues

4. The principle of countercurrent flow facilitates efficient respiration in gills of fishes

In the tissues, high concentrations of carbon doxide

1. increases the affinity of haemoglobin to both oxygen and hydrogen

2. increases the affinity of haemoglobin to oxygen but decreases its affinity to hydrogen

3. decreases the affinity of haemoglobin to oxygen but increases its affinity to hydrogen

4. decreases the affinity of haemoglobin to both oxygen and hydrogen.

During winter a person died during sleep, the room was closed and a container with burnt

charcoal was found in the room. What may be the possible reason of his death?

1. non-availability of oxygen

2. Hb has more affinity to combine with carbon monoxide

3. Hb has more affinity to combine with nitrogen

4. combined effect of 1. and 3.

The respiratory centre in the brain is stimulated by

1. CO₂ concentration in venous blood

2. O₂ concentration in artery blood

3. CO₂ concentration in artery blood

4. O₂ concentration in venous blood.

Which of the following match is correct?

1. Emphysema : reduction of surface area of alveoli and bronchi

2. Pneumonia : occupational disease with asbestos

3. Silicosis : inflammation of alveoli

4. Asthma : excessive secretion of bronchial mucus

When a man inhales air containing normal concentration of O₂ as well as CO he suffers from suffocation because

(1) CO reacts with O₂ reducing its percentage in air

(2) haemoglobin combines with CO instead of O₂ and forms carboxyhaemoglobin

(3) CO affects diaphragm and intercostal muscles

(4) CO affects the nerves of the lungs.

Respiration is controlled by

1. medulla oblongata

2. cerebellum

3. hypothalamus

4. cerebrum

Chemosensitive area of respiratory centre medulla is affected by

1. less CO₂ and H⁺ ions

2. less O₂ and H⁺ ions

3. excess CO₂ and H⁺ ions

4. excess O₂ and H⁺ ions.

Oxygen binding to haemoglobin in blood is

1. directly proportional to the concentration of CO₂ in the medium

2. inversely proportional to the concentration of CO₂ in the medium

3. directly proportional to the concentration of CO in the medium

4. independent of the concentration of CO in the medium.