Gas Exchange

Question 1

Fick’s law

Answer 1

Rate of diffusion
= (Difference in conc. x Surface area) / Diffusion distance

Question 2

Movement of oxygen in insect

Answer 2

• Enters insect through spiracles into tracheae
• spiracles close
• oxygen diffuses through tracheae into tracheoles (DOWN concentration gradient)
• O2 delivered directly to respiring tissues

Question 3

Adaptations of insect to limit water loss

Answer 3

Waterproof coating; rigid exoskeleton covered with waterproof cuticle

Question 4

What happens to SA:Vol ratio when an organism gets larger?

Answer 4

Decreases

Question 5

Name 2 adaptations of insects to minimise water loss

Answer 5

• Relatively small SA:Vol ratio to minimise area over which water is lost
• Rigid exoskeleton covered with waterproof cuticle

Question 6

Explain 3 ways in which an insect’s tracheal system is adapted for efficient gas exchange

Answer 6

• Highly branched tracheoles for larger SA for gas exchange / shorter diffusion distance
• Tracheoles have thin walls so shorter diffusion distance between tracheoles and respiring cells (increase R.O.D)
• Body can be moved by muscles to cause mass movement of air to increase rate of gas exchange

Question 7

Explain 2 ways in which the structure of fish gills is adapted for efficient gas exchange

Answer 7

• Many filaments/lamellae so large surface area
• Lamellae thin for shorter diffusion distance