Gas Exchange - Insects

Question 1

How does the respiration strategy of insects differ from most active animals?

Answer 1

They bring the gas exchange surface close to all cells in their bodies

Question 2

What is the structure of the respiratory system in insects?

Answer 2

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

Question 3

How are the trachea distributed throughout the body of the insect?

Answer 3

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

Question 4

What is the fluid that sometimes fills the tracheoles?

Answer 4

Hemolymph. Is also the circulatory fluid

Question 5

Why do insects put hemolymph in the trachea?

Answer 5

Reduces the risk of drying out when at rest

Question 6

What structure in mammals are the insect tracheoles analogous to?

Answer 6

Alveoli

Question 7

What is the main site of gas exchange in insects?

Answer 7

The tracheoles

Question 8

What happens to the hemolymph when the insect is flying?

Answer 8

Gets reabsorbed into the body to allow gas to reach deeper into the trachea and allow better gas exchange

Question 9

What two equations relate to the amount of liquid in the trachea and the rate of diffusion?

Answer 9

Henry’s law and the Fick equation

Question 10

How is the rate of diffusion enhanced while the insect is flying?

Answer 10

The oxygen getting used up creates a negative pressure in the tracheoles and draws oxygen down towards the tissues

Question 11

Why is there a limit to the pressure gradient diffusion strategy?

Answer 11

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

Question 12

What are 3 strategies insects use to reduce the amount of time it takes for air to diffuse into the tracheoles?

Answer 12

Discontinuous ventilation, conspicuous ventilation and microscopic ventilation

Question 13

What is conspicuous ventilation?

Answer 13

Contraction of the thoracic or abdominal muscles drives air movements

Question 14

What is microscopic ventilation?

Answer 14

Fine contractions and relaxations of the trachea to move air quickly through the tubes

Question 15

What are two strategies used by aquatic insects for breathing underwater?

Answer 15

Bubbles and plastrons

Question 16

What two laws are very important for aquatic insects?

Answer 16

Henry’s law and the ideal gas law

Question 17

What is inside the air bubbles used by diving beetles?

Answer 17

A mix of gases, containing mostly oxygen and nitrogen

Question 18

What is happening to the gases inside an air bubble?

Answer 18

They are being used up with respiration, and diffusing in and out of the bubble according to their partial pressures and solubility

Question 19

Why does the bubble shrink?

Answer 19

Increased volume of nitrogen and decreased volume of oxygen

Question 20

What is a plastron?

Answer 20

Dense layer of water repelling hydrofuge hairs that surround the spiracles of certain insects

Question 21

How do plastrons work?

Answer 21

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

Question 22

Where does the oxygen come from as insects with plastrons use it up?

Answer 22

Diffuses in from the water and the nitrogen diffuses out

Question 23

What is the partial pressure of nitrogen and oxygen inside an air bubble at low depths?

Answer 23

High nitrogen partial pressure and lower oxygen partial pressure

Question 24

In air bubbles at low depths, which way do nitrogen and oxygen diffuse?

Answer 24

Nitrogen diffuses out, oxygen diffuses in

Question 25

What happens to the carbon dioxide exhaled by aquatic insects?

Answer 25

It quickly dissolves in water and only makes up a minimal part of the pressure in the bubble

Question 26

What happens to the air bubble at moderate depths?

Answer 26

The total pressure increases because of the additional water pressure, and the bubble shrinks