Gas Exchange: Insect

Question 1

Explain how the body surface of a single-celled organism is adapted for gas exchange:

Answer 1

1. Thin, flat shape and large surface area to volume ratio
2. Short diffusion distance to all parts of cell → rapid diffusion eg. of O2 / CO2

Question 2

Describe the tracheal system of an insect:

Answer 2

1. Spiracles = pores on surface that can open / close to allow diffusion
2. Tracheae = large tubes full of air that allow diffusion
3. Tracheoles = smaller branches from tracheae, permeable to allow gas exchange with cells

Question 3

Explain how an insect’s tracheal system is adapted for gas exchange: Abdomen Pumping

Answer 3

1. Contraction of abdominal muscles (abdominal pumping) changes pressure in body, causing air to move in / out
2. Maintains concentration gradient for diffusion.
   3.Fluid in end of tracheoles drawn into tissues by osmosis during exercise (lactate produced in anaerobic respiration lowers ψ of cells).
   4.As fluid is removed, air fills tracheoles. So rate of diffusion to gas exchange surface increases as diffusion is faster through air

Question 4

Explain how an insect’s tracheal system is adapted for gas exchange: Tracheoles

Answer 4

1. Tracheoles have thin epithelial cell layer.
2. So short diffusion distance to cells.
   3.High numbers of highly branched tracheoles
3. So short diffusion distance to cells. So large surface area

Question 5

Explain how an insect’s tracheal system is adapted for gas exchange: Tracheae

Answer 5

Tracheae provide tubes full of air
○ So fast diffusion

Question 6

Explain structural and functional compromises in terrestrial insects that allow efficient gas exchange while limiting water loss:

Answer 6

1. Thick waxy cuticle / exoskeleton → Increases diffusion distance so less water loss (evaporation)
2. Spiracles can open to allow gas exchange AND close to reduce water loss (evaporation)
3. Hairs around spiracles → trap moist air, reducing ψ gradient so less water loss (evaporation)