A Level Biology Practice Exam

What does the tracheal system in insects consist of?

1. A network of blood vessels

2. A system of air filled tubes

3. A series of digestive organs

4. A framework of muscle fibers

The correct answer is: A system of air filled tubes

The tracheal system in insects consists of a specialized network of air-filled tubes that transport oxygen directly to the tissues and cells. This system begins with small openings on the surface of the insect, called spiracles, which lead into a series of branching tubes known as tracheae. These tubes are highly efficient for gas exchange because they deliver oxygen directly to the cells without the need for a circulatory fluid to transport it, as seen in many other organisms. The primary function of the tracheal system is to facilitate the diffusion of oxygen from the atmosphere to internal tissues while simultaneously allowing carbon dioxide produced by respiration to exit the body. Unlike blood vessels, the tracheal system does not rely on a pumping mechanism like a heart; instead, the movement of air within the tubes can be influenced by the insect's movements and changes in body pressure. This adaptation is particularly effective for the small size and high metabolic demands of insects, making it essential for their survival.