Zoology MCQs for NEET — Practice Questions with Answers

The correct pathway for air to reach the lungs is: Nostrils → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli. This sequence ensures that the air is properly filtered, warmed, and humidified before reaching the delicate alveolar sacs where gas exchange occurs.

The volume of air breathed in and out during effortless respiration is known as the tidal volume. It represents the normal amount of air exchanged with each breath without any extra effort. For a healthy adult, the tidal volume typically ranges from 500 to 600 milliliters.

At high altitudes, the oxygen levels are lower. To compensate for the reduced oxygen availability, the body increases the number of red blood cells (RBCs) to enhance the oxygen-carrying capacity of the blood. This process is called erythropoiesis and is stimulated by the hormone erythropoietin.

The maximum amount (70-75%) of carbon dioxide is transported in the blood in the form of bicarbonate ions (HCO3-). When CO2 enters the red blood cells, it reacts with water to form carbonic acid (H2CO3), which quickly dissociates into bicarbonate and hydrogen ions. This reaction is catalyzed by the enzyme carbonic anhydrase.

Oxygen is primarily transported in the blood bound to hemoglobin in red blood cells (RBCs). Carbon dioxide is transported in the blood in three forms: dissolved in plasma, as bicarbonate ions, and bound to hemoglobin (carbaminohemoglobin). Therefore, both oxygen and carbon dioxide are transported through RBCs and plasma.

Tidal volume is the amount of air that is inhaled or exhaled during normal, relaxed breathing. It has the lowest value compared to other respiratory volumes like vital capacity, inspiratory reserve volume, and expiratory reserve volume. Vital capacity is the maximum amount of air a person can expel from the lungs after a maximum inhalation, and both inspiratory and expiratory reserve volumes are additional volumes of air that can be inhaled or exhaled beyond the normal tidal volume.

A molecule of hemoglobin can carry up to 4 oxygen molecules. Hemoglobin has four subunits, each containing an iron atom that can bind to one molecule of oxygen. Thus, one hemoglobin molecule can transport four oxygen molecules.

Haemoglobin is a respiratory pigment found in red blood cells. It binds to oxygen in the lungs and transports it to tissues throughout the body. This is essential for cellular respiration, where oxygen is used to produce energy.

The vocal cords are located in the larynx, commonly known as the voice box. They vibrate to produce sound when air passes through them during exhalation, enabling speech and other vocalizations.