6.1 and 2 : Gas exchange in insects
How are insects adapted to reduce water loss? - correct answer ✔✔1. Waterproof/waxy cuticle all over
their body surfaces = reduce evaporation.
2. Small SA:V ratio = minimize area over which water is lost.
3. Spiracles may be open and closed by a valve.
- When open, water may evaporate from the insect.
- Much of the time insects keep their spiracles closed to prevent this water loss.
- Periodically they open them to allow gas exchange.
4. Tiny hairs around spiracles = reduces evaporation.
What is the structure of the gas exchange system of an insect? - correct answer ✔✔1. Internal network
of tubes = tracheae
2. Tracheae are supported by strengthened rings to stop them collapsing
3. Tracheae divide into smaller tubes called tracheoles
4. Tracheoles extend throughout the body tissues of the insect = in this way air and the oxygen it
contains is brought directly to the respiring tissues. They have thin permeable walls and go to individual
cells.
How does the gas exchange surface of an insect work? - correct answer ✔✔1. Air diffuses into tracheae
through spiracles. Respiring cells use O2, so lowers [O2] so O2 diffuses down concentration gradient
towards the ends of the tracheoles where respiring cells are
2. CO2 produced by respiring cells move down concentration gradient along tracheoles, into tracheae,
towards spiracles to be released into the atmosphere.
3. Insects use rhythmic abdominal movements to move air in and out of spiracles - speeds up gas
exchange.
= DIFFUSION IN AIR IS MUCH MORE RAPID THAn IN WATER, GASES EXCHANGED QUICKLY BY THIS
METHOD.
, What is the trade off between gas exchange and water loss in insects reduced? - correct answer ✔✔-
Spiracles can be opened and closed by valves
- Small exposed SA:V to less water evaporates
- Waterproof coverings/ waxy cuticle
- Tiny hairs around spiracles reduce evaporation.
How it works = via ventilation - correct answer ✔✔1. Movement of muscles in insects can create mass
movements of air in and out of the tracheae.
2. This further speeds up the exchange of respiratory gases.
3. This is because an insects circulatory system DOES NOT transport oxygen
What feature do the trachea have? - correct answer ✔✔Have thin, permeable walls
Limitations of this gas exchange system - correct answer ✔✔1. Relies mostly on diffusion to exchange
gases between the environment and cells.
- For diffusion to be effective, diffusion pathway needs to be short.
- This limits the size that insects can attain.
Advantage of liquid in tracheoles passing into muscle fibres during flight? - correct answer ✔✔larger
surface area for gaseous exchange
Substances produced during metabolism cause liquid in tracheoles to pass into muscle fibre during flight,
explain how. - correct answer ✔✔lowers water potential of tissues;
liquid moves in by osmosis;
Explain why a muscle fibre cannot be large than 20 micrometres in diameter - correct answer ✔✔1.
diffusion pathway is too long/related to
surface area to volume ratio;
2. to supply enough oxygen;
Abdominal pumping increases the efficiency of gas exchange between the tracheoles
How are insects adapted to reduce water loss? - correct answer ✔✔1. Waterproof/waxy cuticle all over
their body surfaces = reduce evaporation.
2. Small SA:V ratio = minimize area over which water is lost.
3. Spiracles may be open and closed by a valve.
- When open, water may evaporate from the insect.
- Much of the time insects keep their spiracles closed to prevent this water loss.
- Periodically they open them to allow gas exchange.
4. Tiny hairs around spiracles = reduces evaporation.
What is the structure of the gas exchange system of an insect? - correct answer ✔✔1. Internal network
of tubes = tracheae
2. Tracheae are supported by strengthened rings to stop them collapsing
3. Tracheae divide into smaller tubes called tracheoles
4. Tracheoles extend throughout the body tissues of the insect = in this way air and the oxygen it
contains is brought directly to the respiring tissues. They have thin permeable walls and go to individual
cells.
How does the gas exchange surface of an insect work? - correct answer ✔✔1. Air diffuses into tracheae
through spiracles. Respiring cells use O2, so lowers [O2] so O2 diffuses down concentration gradient
towards the ends of the tracheoles where respiring cells are
2. CO2 produced by respiring cells move down concentration gradient along tracheoles, into tracheae,
towards spiracles to be released into the atmosphere.
3. Insects use rhythmic abdominal movements to move air in and out of spiracles - speeds up gas
exchange.
= DIFFUSION IN AIR IS MUCH MORE RAPID THAn IN WATER, GASES EXCHANGED QUICKLY BY THIS
METHOD.
, What is the trade off between gas exchange and water loss in insects reduced? - correct answer ✔✔-
Spiracles can be opened and closed by valves
- Small exposed SA:V to less water evaporates
- Waterproof coverings/ waxy cuticle
- Tiny hairs around spiracles reduce evaporation.
How it works = via ventilation - correct answer ✔✔1. Movement of muscles in insects can create mass
movements of air in and out of the tracheae.
2. This further speeds up the exchange of respiratory gases.
3. This is because an insects circulatory system DOES NOT transport oxygen
What feature do the trachea have? - correct answer ✔✔Have thin, permeable walls
Limitations of this gas exchange system - correct answer ✔✔1. Relies mostly on diffusion to exchange
gases between the environment and cells.
- For diffusion to be effective, diffusion pathway needs to be short.
- This limits the size that insects can attain.
Advantage of liquid in tracheoles passing into muscle fibres during flight? - correct answer ✔✔larger
surface area for gaseous exchange
Substances produced during metabolism cause liquid in tracheoles to pass into muscle fibre during flight,
explain how. - correct answer ✔✔lowers water potential of tissues;
liquid moves in by osmosis;
Explain why a muscle fibre cannot be large than 20 micrometres in diameter - correct answer ✔✔1.
diffusion pathway is too long/related to
surface area to volume ratio;
2. to supply enough oxygen;
Abdominal pumping increases the efficiency of gas exchange between the tracheoles
