Correct Option
The correct option is (a).
Explanation
The tracheal system is a specialized respiratory network primarily found in insects and certain other terrestrial arthropods. It functions to transport respiratory gases directly between the external environment and the body tissues, bypassing the need for a liquid transport medium for oxygen.
Statement-wise Analysis
- Statement 1 is Correct: The tracheal system consists of an elaborate network of air tubes known as tracheae, which subdivide into finer tubes called tracheoles. These tubes permeate the body tissues of insects, allowing air to reach cells directly.
- Statement 2 is Incorrect: A defining feature of the tracheal system is that it does not rely on blood (hemolymph) to transport oxygen. In insects, the hemolymph transports nutrients and waste but lacks respiratory pigments like hemoglobin for oxygen transport. Instead, oxygen diffuses directly through the tracheal tubes to the tissues.
- Statement 3 is Incorrect: The tracheal system is specific to insects and some arthropods. The primary respiratory system in humans consists of the lungs and the respiratory tract (including the trachea or windpipe, which is structurally different and part of the pulmonary system), relying on blood circulation to transport gases.
Key Takeaway: The tracheal system in insects facilitates direct gas exchange between the atmosphere and body cells without the involvement of the circulatory system, unlike the pulmonary system in humans where blood acts as the transport medium.