Gas Exchange in Insects

Question 1

When spiracles are closed…

Answer 1

oxygen concentration decreases at a constant rate and then levels off, indicating it is at its lowest possible concentration.

Question 2

What causes spiracles to open

Answer 2

A spike in CO2 conc. (/pp) in trachea

Blood becomes too acidic

Question 3

Advantages of spiracles

Answer 3

Helps to decrease water loss by diffusion, while allowing gas exchange

Question 4

CO2 removal from a single-called organism

Answer 4

Diffusion over the cell surface

Question 5

Conflict between water retention and gas exchange

Answer 5

Increasing surface area, thinness and permeability is beneficial for gas exchange because it increases the interface area, but it also increases the rate of evaporation (because conserving water needs thick, waterproof surfaces and a small SA), decreasing water conservation.

Question 6

How tracheal system limits insect size

Answer 6

The tracheoles have to extend throughout the body tissues of the insect for the oxygen to be transported via simple diffusion– tissues that were too far away would not receive sufficient oxygen (in sufficient time for aerobic respiration) and would die

Question 7

Tracheal adaptations

Answer 7

• very close to respiring body cells through the branching – provides short diffusion pathway and large surface area
• can be opened wider to allow a greater concentration of air to flow into the trachea
• tracheal fluid
• thin walls
• ventilation to maintain diffusion
• trachea are full of air

Question 8

Tracheal fluid

Answer 8

osmoses from a high water potential to a low water potential into anaerobically repsiring cells due to the production of soluble lactate decreasing their water potential, increasing the volume of the tracheoles and therefore decreasing the pressure, allowing more air to flow into the tracheoles to equalise the pressure.

Question 9

When an insect is at rest

Answer 9

• oxygen undergoes simple diffusion from a high concentration to a low concentration from the atmosphere into the trachea
• the oxygen diffuses down the trachea into the tracheoles and then into the respiring cells which are using up oxygen from a high to a low concentration
• oxygen is used in cellular respiration

Question 10

Abdominal pumping

Answer 10

• abdominal pumping is linked to CO2 release
• abdomen contracts, increasing the pressure in the tubes causing the spiracles at the back of the body to open and those at the front, letting CO2 undergo simple diffusion (down a pressure gradient) out of the back of the insect