Organisms Exchange Substances with their Environment: Gas Exchange - Insects

Question 1

Why can’t insects use their bodies as an exhange surface?

Answer 1

• They have a waterproof chitin exoskeleton and a small SA:V in order to reduce water loss

Question 2

Name and describe the three main features of an insect’s gas transport system

Answer 2

• Spiracles
- Holes on the body’s surface which may be opened or closed by a valve for gas or water exchange

•Tracheae
- Large tubes extending through all body tissues, supported by rings to prevent collapse

• Tracheoles
- Smaller branches dividing off the tracheae

Question 3

Explain the process of gas exchange in insects

Answer 3

• Gases move in and out of the tracheae through the spiracles
• A diffusion gradient allows oxygen to diffuse into the body tissue while waste CO2 diffuses out
• Tracheae branch off into tracheoles which have thin, permeable walls and go to individual cells
• Ventilation mechanism -contraction of muscles in the tracheae allows mass movement of air in and out of spiracles

Question 4

How is a diffusion gradient established in insects?

Answer 4

• As cells are respiring oxygen is used up
• This creates a low concentration of oxygen in the cells
• Oxygen diffuses into cells
• As carbon dioxide is produced this has a high concentration in the cells
• CO2 diffuses out of cells
• Diffusion gradients are set up and as diffusion is more rapid in air than water gases can be exchanged efficiently

Question 5

How do insects control water loss?

Answer 5

• They have a waterproof exoskeleton that is covered with waterproof chitin
• They have small SA:V
• Spiracles can be closed with valves to reduce water loss
• They have hairs around their spiracles that traps water vapour, which reduces Ψ gradient which therefore reduces water loss