The correct option is (a).
Explanation
Insects possess a specialized respiratory system known as the tracheal system. Unlike vertebrates, insects do not rely on their circulatory system for gas exchange. Instead, they utilize a network of tubes that deliver oxygen directly to body tissues.
Statement-wise Analysis
- Statement 1 is Correct. Insects breathe through small openings on the sides of their body called spiracles. Oxygen-rich air enters through these spiracles and moves into a network of tubes called tracheal tubes, which further branch into finer tubes known as tracheoles to reach individual cells.
- Statement 2 is Incorrect. In insects, the blood (hemolymph) does not transport oxygen. It generally lacks respiratory pigments like haemoglobin (which is found in vertebrates). Instead, the tracheal tubes facilitate the direct diffusion of oxygen from the air to the tissues.
- Statement 3 is Incorrect. Carbon dioxide produced during cellular respiration diffuses out of the cells into the tracheal tubes and is expelled through the spiracles. Starch is a polysaccharide produced by plants through photosynthesis; it is not synthesized by insects from carbon dioxide.
Key Takeaway: The respiratory system of insects consists of spiracles and tracheal tubes that transport gases directly to and from cells, independent of the circulatory system (hemolymph), which lacks haemoglobin.