Gas Exchange - Insects Flashcards
How does the respiration strategy of insects differ from most active animals?
They bring the gas exchange surface close to all cells in their bodies
What is the structure of the respiratory system in insects?
They have a bunch of blind-end trachea that are filled with gas and end at the tissues. The tubes are open to the atmosphere through spiracles
How are the trachea distributed throughout the body of the insect?
They branch throughout the entire body of the insect and end in very fine, thin walled tracheoles. More tracheoles will go to more metabolically active tissues
What is the fluid that sometimes fills the tracheoles?
Hemolymph. Is also the circulatory fluid
Why do insects put hemolymph in the trachea?
Reduces the risk of drying out when at rest
What structure in mammals are the insect tracheoles analogous to?
Alveoli
What is the main site of gas exchange in insects?
The tracheoles
What happens to the hemolymph when the insect is flying?
Gets reabsorbed into the body to allow gas to reach deeper into the trachea and allow better gas exchange
What two equations relate to the amount of liquid in the trachea and the rate of diffusion?
Henry’s law and the Fick equation
How is the rate of diffusion enhanced while the insect is flying?
The oxygen getting used up creates a negative pressure in the tracheoles and draws oxygen down towards the tissues
Why is there a limit to the pressure gradient diffusion strategy?
It takes time for the oxygen to diffuse, so the insect will have a problem if it is using up the oxygen faster than it can diffuse
What are 3 strategies insects use to reduce the amount of time it takes for air to diffuse into the tracheoles?
Discontinuous ventilation, conspicuous ventilation and microscopic ventilation
What is conspicuous ventilation?
Contraction of the thoracic or abdominal muscles drives air movements
What is microscopic ventilation?
Fine contractions and relaxations of the trachea to move air quickly through the tubes
What are two strategies used by aquatic insects for breathing underwater?
Bubbles and plastrons
What two laws are very important for aquatic insects?
Henry’s law and the ideal gas law
What is inside the air bubbles used by diving beetles?
A mix of gases, containing mostly oxygen and nitrogen
What is happening to the gases inside an air bubble?
They are being used up with respiration, and diffusing in and out of the bubble according to their partial pressures and solubility
Why does the bubble shrink?
Increased volume of nitrogen and decreased volume of oxygen
What is a plastron?
Dense layer of water repelling hydrofuge hairs that surround the spiracles of certain insects
How do plastrons work?
The gas is trapped along the surface of the body as a thin film of gas, and the hairs maintain surface tension so the bubble never shrinks and the insect never needs to resurface
Where does the oxygen come from as insects with plastrons use it up?
Diffuses in from the water and the nitrogen diffuses out
What is the partial pressure of nitrogen and oxygen inside an air bubble at low depths?
High nitrogen partial pressure and lower oxygen partial pressure
In air bubbles at low depths, which way do nitrogen and oxygen diffuse?
Nitrogen diffuses out, oxygen diffuses in
What happens to the carbon dioxide exhaled by aquatic insects?
It quickly dissolves in water and only makes up a minimal part of the pressure in the bubble
What happens to the air bubble at moderate depths?
The total pressure increases because of the additional water pressure, and the bubble shrinks
