6.2 Gas Exchange In Single-celled Organisms And Insects

Question 1

How does gas exchange in a single-called organism work?

Answer 1

O2 diffused through cell-surface membrane, likewise CO2 is diffused out of the cell-surface membrane.

Question 2

Insects have evolved a network of tubes called ________.

Answer 2

Tracheae

Question 3

The tracheae divide into smaller dead end tubes called _________.

Answer 3

Tracheoles

Question 4

How do respiratory gases move in and out of the tracheal system in insects? (3)

Answer 4

• along a diffusion gradient
• mass transport
• ends of tracheoles filled with water

Question 5

Why are the ends of tracheoles filled with water?

Answer 5

As the insect anaerobically respirates, lactate is produced which lowers the water potential in the muscles, water therefore moves into the tracheoles by osmosis. More air is drawn into the tracheoles and the final diffusion pathway is liquid which increases the rate at which oxygen is diffused.

Question 6

What are the tiny pores that gases enter and exit the tracheae called?

Answer 6

Spiracles

Question 7

What reinforces the tracheae to keep it open?

Answer 7

Chitin

Question 8

What are 5 ways that an insects tracheal system is adapted for efficient gas exchange?

Answer 8

• tracheoles have thin walls for short diffusion pathway
• there’s a large number of tracheoles, therfore a large SA:V
• tubes are full of air so diffusion is fast
• fluid at end of tracheoles so diffusion is faster when exercising
• air is squeezed through by muscles to maintain a conc. grad.