A Level Biology Practice Exam

What is the primary function of tracheal fluid in insects?

1. To aid in digestion

2. To control surface area for gas exchange and water loss

3. To transport nutrients

4. To protect against pathogens

The correct answer is: To control surface area for gas exchange and water loss

The primary function of tracheal fluid in insects is to control surface area for gas exchange and water loss. Tracheal fluid plays a crucial role in the insect respiratory system, which relies on a network of tubes (tracheae) that deliver oxygen directly to the tissues. The fluid can help regulate the amount of air that enters and exits these tubes by adjusting the surface area available for gas exchange. By controlling the surface area, tracheal fluid facilitates efficient oxygen uptake while minimizing water loss, which is particularly important for terrestrial insects that need to conserve moisture in their bodies. Insects do not have a circulatory system that transports gases like vertebrates do; instead, they rely on these adaptations in their tracheal system to maintain their respiratory efficiency. The presence of tracheal fluid allows insects to fine-tune their respiratory processes based on their activity levels and environmental conditions, a critical aspect of their survival.