6.2 - Gas Exchange in Insects

Question 1

How does lactate accumulation affect the rate of gas exchange: (3)

Answer 1

1. Lactate accumulation reduces water potential in tracheal fluid at the end of tracheoles
2. water leaves the tracheoles via osmosis
3. higher SA is exposed to gas exchange

Question 2

Ventilation mechanisms in insects (5)

Answer 2

1. mechanical active ventilation - when the muscles around the tracheae contract and relax - changing the volume and pressure in the abdomen and squeezing the tracheae to pump air in and out of the spiracles
2. tracheal fluids - moves out into the tissues during exercise to increase the diffusion rate and SA for gas exchange
3. enlarged collapsible tracheae, or accessory sacs and air reservoirs - these inflate or deflate to ventilate the tracheal system and increase the volume of air moved through the system
4. wing muscles connected to sacs - pump air to ventilate the tracheal system
5. vibration of thoracic muscles - pump air to ventilate the tracheal system

Question 3

how is the conc gradient between the tissues and air in the tracheal system maintained (3)

Answer 3

1. cells using up oxygen for respiration - keeps oxygen conc low in cells
2. cells producing CO2 in respiration - keeps CO2 conc high in cells
3. continuous ventilation - fresh air is supplied to the tracheal system via spiracles

Question 4

Stages of gas exchange in insects

Answer 4

1. air enters the tracheal system through open spiracles
2. air moves into larger tracheae and diffuses into smaller tracheoles
3. tracheoles branch throughout the body, transporting air directly to cells
4. oxygen dissolves in water in tracheal fluid and diffuses down its conc gradient from tracheoles into body cells
5. CO2 diffuses down its conc gradient out of body cells into the tracheoles
6. air is then diffused back to the spiracles via the tracheae and relreased from the body

Question 5

Adaptations of spiracles:

Answer 5

open and close - allows them to control gas exchange with the atmosphere and minimise water loss

Question 6

Adaptations of tracheoles (5):

Answer 6

1. penetrate directly into tissues
2. thin walls - reduce the gas diffusion distance
3. highly branched - maximises the SA
4. not reinforced with chitin - allows gas exchange to occur
5. fluids at the end of the tracheoles - allows oxygen to dissolve to aid diffusion and reduces water loss

Question 7

Adaptations of the tracheae (2):

Answer 7

1. reinforced with spirals of chitin - prevents collapsing
2. mutliple tracheae - increases SA

Question 8

Main structures in the gas exchange system of insects: (3)

Answer 8

1. trachae - air filled tubes branching throughout the body
2. tracheoles - fine branches of tracheae that deliver gases to cells
3. spiracles - external opening of the tracheal system on the exoskeleton along the abdomen and thorax

Question 9

What is an insect’s exoskeleton covered with to help prevent water loss?

Answer 9

A waterproof cuticle

Question 10

Adaptations of insect gas exchange systems to balance two conflicting needs (2):

Answer 10

1. maximising gas exchange efficiency
2. minimising water loss

Question 11

Why do insects require gas exchange? (2)

Answer 11

1. to deliver oxygen to cells - allows aerobic respiration to occur to release energy for cellular processes
2. to remove CO2 from cells - a waste product of respiration which reduces pH - can denature enzymes