7.4a - Ventilation & Gas Exchange in other Organisms

Question 1

What features of insects means little to no gas exchange can take place?

Answer 1

Insects have a high oxygen demand

• Hard exoskeleton so no gas can diffuse
• No blood pigments to carry oxygen

Question 2

What is a spiracle and its function?

Answer 2

• Small openings along thorax and abdomen of an insects.
• Air enters and leaves the spiracles, but water is also lost

Question 3

If spiracles lead to water loss, how do insects maximise gas exchange and minimise water loos?

Answer 3

• Sphincters open and close spiracles
• Sphrinter are closed most of the time (to reduce water loss)
• When CO₂ levels rise or O₂ demand increases, sphincters open spiracle

Question 4

What is the structure of an insect ventilation system?

Answer 4

• Leading from the spiracles is the tracheae
  
  • Which run parallel to the insect’s body
• From the trachea branch the tracheoles into respiring tissue/muscles
  
  • They run adjacent to the tracheae

Question 5

What are the adaptations of the tracheae?

Answer 5

• Largest tube of the insect respiratory system
• Lined with chitin - impermeable to gas so no gas exhange occurs in the tracheae

Question 6

What are the features and functions of the tracheoles?

Answer 6

• Each tracheole is a single elongated cell
• Has no chitin so freely permeable to gas
• Small size so they spread between tissues for gas exchange

Question 7

How is gaseous exchanged performed in an insect?

Answer 7

• Air moves along tracheae and tracheoles by diffusion
• Tracheoles have large surface area for diffusion
• Oxygen dissolves into moisture of walls and diffuses into necessary cells

Question 8

What is the function of tracheal fluid?

Answer 8

Tracheal fluid exists at the ends of the tracheoles, it is in contact with fluid and cells of the insect’s body

When insect is @ rest:

• Fluid enters from body cells into end of tracheoles

When insect is active and muscles respiring:

• Muscles draw tracheal fluid from tracheole
• Fluid has O₂ which diffuses directly into respiring cells
• Once the fluid leaves the tracheoles, it increases SA for direct O₂ diffusion into cells
• Fluid leaving lowers tracheolar pressure, drawing more air in

Question 9

What alternative methods for increasing gas exchange in insects?

Answer 9

Mechanical Ventilation:

• Air actively pumped by muscular pumping of the thorax and abdomen
• Causing pressure changes which maximises the volume of air drawn in or expired

Collapsible Air Sacs:

• They are air reservoirs
• Used to increase amount of air moved through gas exchange system
• Inflated and deflated by thorax/abdomen