7.4.1 - Ventilation and gas exchange in other organisms (insects)

Question 1

What are the main characteristics of the insect gas exchange system?

Answer 1

1. Oxygen is delivered directly to cells via tracheae and tracheoles.
2. The system is adapted to minimize water loss while maximizing gas exchange efficiency.

Question 2

Why don’t insects rely on blood pigments for oxygen transport?

Answer 2

The tracheal system directly supplies oxygen to cells, making blood pigments unnecessary.

Question 3

How is carbon dioxide removed in insects?

Answer 3

CO₂ diffuses out of the cells, through tracheoles and tracheae, and exits via spiracles.

Question 4

Why is minimizing water loss essential for insects?

Answer 4

Insects live in dry environments where dehydration is a significant threat.

Question 5

What adaptations help insects balance water conservation and gas exchange?

Answer 5

1. Controlled spiracle opening
2. Impermeable exoskeleton
3. Regulated tracheal fluid.

Question 6

What are spiracles, and where are they located?

Answer 6

Small openings along the thorax and abdomen for air entry and exit.

Question 7

What controls spiracle opening and closing?

Answer 7

Sphincters regulate spiracle activity to conserve water or increase gas exchange.

Question 8

How do spiracles respond to oxygen and carbon dioxide levels?

Answer 8

Spiracles open when oxygen demand is high or CO₂ levels build up.

Question 9

What happens to spiracles when the insect is inactive?

Answer 9

Spiracles are kept closed to minimize water loss.

Question 10

What are tracheae, and what is their structure?

Answer 10

Large tubes up to 1 mm in diameter, lined with chitin spirals for support.

Question 11

Why do tracheae have chitin linings?

Answer 11

To keep them open during movement or compression, ensuring uninterrupted airflow.

Question 12

Why is gas exchange limited in the tracheae?

Answer 12

The chitin lining is impermeable, so diffusion occurs mainly in the tracheoles.

Question 13

What are tracheoles, and how are they structured?

Answer 13

Fine tubes (0.6–0.8 µm in diameter), unlined and permeable to gases, extending to individual cells.

Question 14

Why are tracheoles highly efficient for gas exchange?

Answer 14

They provide a large surface area and a short diffusion distance.

Question 15

How do tracheoles interact with cells?

Answer 15

They penetrate tissues and run between cells, directly delivering oxygen.

Question 16

What role does tracheal fluid play in gas exchange?

Answer 16

It dissolves oxygen for diffusion and regulates surface area exposure by retracting during high oxygen demand.

Question 17

How is air transported through the tracheal system?

Answer 17

By passive diffusion along a concentration gradient.

Question 18

What factors enhance diffusion efficiency in insects?

Answer 18

Short diffusion distances and a high surface area provided by numerous tracheoles.

Question 19

Why is passive diffusion sufficient for most insects?

Answer 19

Their small size allows oxygen to reach cells quickly without active transport.

Question 20

What happens to tracheal fluid during intense activity?

Answer 20

Lactic acid buildup lowers water potential, causing fluid to be withdrawn by osmosis.

Question 21

How does withdrawing tracheal fluid improve gas exchange?

Answer 21

It exposes more tracheole surface area, increasing oxygen diffusion rates.

Question 22

Why do some insects require additional gas exchange adaptations?

Answer 22

Activities like flying require more oxygen than passive diffusion can supply.

Question 23

What is mechanical ventilation in insects?

Answer 23

Muscular movements of the thorax and abdomen pump air through the tracheal system.

Question 24

How do air sacs support gas exchange in high-energy insects?

Answer 24

Collapsible air sacs store and move large volumes of air to meet oxygen demands.

Question 25

Why can’t insects grow very large?

Answer 25

The tracheal system relies on diffusion, which is inefficient over long distances.

Question 26

What limits oxygen delivery in larger body sizes?

Answer 26

Increased diffusion distances reduce efficiency, making large sizes unsustainable.

Question 27

How has the insect respiratory system evolved for terrestrial life?

Answer 27

Impermeable exoskeletons and spiracles minimize water loss, while tracheoles ensure direct oxygen delivery.

Question 28

How does the exoskeleton affect gas exchange?

Answer 28

It’s tough, impermeable nature necessitates specialized structures like spiracles.

Question 29

How does flying increase oxygen demand in insects?

Answer 29

Intense muscle activity during flight requires rapid oxygen delivery to cells.

Question 30

How do insects meet increased oxygen demand during flight?

Answer 30

They use mechanical ventilation, withdraw tracheal fluid, and rely on air sacs.

Question 31

How do spiracles minimize water loss?

Answer 31

By staying closed during inactivity or low oxygen demand.

Question 32

What triggers spiracles to open?

Answer 32

Increased oxygen demand or elevated carbon dioxide levels.

Question 33

How is the insect gas exchange system unique compared to mammals and fish?

Answer 33

• Insects: Direct oxygen delivery through tracheoles without blood involvement.
• Mammals: Alveoli in lungs transfer gases to blood.
• Fish: Counter-current flow in gills maximizes oxygen uptake from water.

Question 34

Why is the insect gas exchange system efficient for its size?

Answer 34

It eliminates the need for blood transport, relying instead on direct diffusion.

Question 35

How do desert insects adapt their respiratory systems for dry environments?

Answer 35

By shortening spiracle opening durations and efficiently using tracheal fluid.

Question 36

Why is water conservation critical in insect gas exchange?

Answer 36

Preventing dehydration is essential for survival in terrestrial habitats.

Question 37

How do thoracic and abdominal movements help gas exchange?

Answer 37

They actively pump air into and out of the tracheal system, increasing airflow.

Question 38

What is the role of air sacs in the tracheal system?

Answer 38

They act as reservoirs, storing and moving larger volumes of air when needed.

Question 39

How does the large surface area of tracheoles improve efficiency?

Answer 39

It maximizes oxygen diffusion directly into cells.

Question 40

Why is the short diffusion distance important in insect gas exchange?

Answer 40

It ensures rapid oxygen delivery and carbon dioxide removal.

Question 41

How can insects increase the level of gas exchange?

Answer 41

1. Mechanical ventilation of the tracheal system
2. Collapsible and large tracheae or air sacs which act as air reservoirs

Question 42

How does the mechanical ventilation of the tracheal system, increase gas exchange?

Answer 42

Air is actively pumped into the system by muscular pumping movements of the thorax and/or the abdomen these movements change the volume of the body and this changes the pressure in the tracheae and tracheoles. Is drawn into the trachea and tracheolis or forced out as the pressure changes.

Question 43

How does the collapsible and large tracheae or air sacs which act as air reservoirs, help gas exchange?

Answer 43

These are used to increase the amount of air Moved Through the gas exchange system they are usually inflated and deflated by the ventilating movement of the thorax and abdomen.