gas exchange in insects (module 3)

Question 1

how is water loss limited in insects?

Answer 1

• chitin in trachea is impermeable so reduce water loss
• spiracles close during inactivity
• small surface area:volume

Question 2

what is the first method of gas exchange in tracheal system?

Answer 2

• open spiracles allow O2 to diffuse into trachea and then into tracheoles

Question 3

what is the second method of gas exchange in tracheal system?

Answer 3

• insects contract and relax abdominal muscles to move gases in and out of tracheoles

Question 4

what is the third method of gas exchange in tracheal system?

Answer 4

• when insects are active it produces lactate in muscle cells
• this reduces the water potential in cells so water moves into cells from tracheoles via osmosis
• this lowers volume in tracheoles bringing more oxygen into them (increase diffusion)

Question 5

how does ficks law apply to gas exchange in insects?

Answer 5

• tracheoles are highly branched so large surface area
• tracheole walls are thin so short diffusion distance to cells
• concentration gradient maintained due to tracheoles near cells have less oxygen than tracheoles further so oxygen diffuses in more often