6.2 gas exchange in single- celled organisms and insects

Question 1

describe how single- celled organisms exchange gases

Answer 1

• oxygen is absorbed by diffusion

- carbon dioxide diffuses

Question 2

what are the 3 ways in which respiratory gases move in and out the tracheal system of the insects

Answer 2

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

Question 3

gas exchange in insects- along a diffusion gradient

Answer 3

• oxygen moves down concentration gradient as oxygen is used up
• carbon dioxide moves down concentration gradient as carbon dioxide is produced

Question 4

gas exchange in insects- mass transport

Answer 4

• contraction of muscles can squeeze trachea

- diffusion is more rapid

Question 5

gas exchange in insects- the ends of the tracheoles are filled with water

Answer 5

• helpful during major activity
• lactate lowers water potential of muscle cells
• water moves in to cells from tracheoles
• final diffusion pathway is now in air not water
• diffusion is more rapid

Question 6

increasing rate of diffusion

Answer 6

• concentration gradient -> moves along diffusion gradient
• surface area-> many tracheoles
• diffusion pathway -> tracheoles brought directly to respiring tissue

Question 7

what are the tiny pores on the insect’s cell body called?

Answer 7

spiracles

Question 8

explain how the tracheal system limits the size of insects

Answer 8

• relies on diffusion to bring oxygen to the respiring tissue
• if insects were large it would take too long for oxygen to reach the tissues rapidly enough to supply their needs

Question 9

explain why there is a conflict in terrestrial insects between gas exchange and conserving water

Answer 9

• gas exchange requires a thin permeable surface with a large area
• conserving water requires thick, waterproof surfaces with a small area