3.2.1 gas exchange (insects)

How is the body of a single celled organism adapted for gas exchange

• thin, flat shape and large SA:V

• Short diffusion pathway to all parts of cell, so rapid diffusion of O2/ CO2

What are the 3 parts of the tracheal system of an insect

1. Spiracles

2. Tracheae

3. Tracheoles

Insect tracheal system — what are the spiracles

Pores on surface that can open/ close to allow diffusion

Insect tracheal system — what is the tracheae

Large tubes full of air that allow diffusion

Insect tracheal system — what are tracheoles

Smaller branches from tracheae, permeable to allow gas exchange with cells

How is an insects tracheal system adapted for gas exchange (the tracheoles)

• have thin walls, so short diffusion distance to cells

• High numbers/ highly branched, so short diffusion distance and large SA

How is an insects tracheal system adapted for gas exchange (the tracheae)

• provide tubes full of air, so fast diffusion

How is an insects tracheal system adapted for gas exchange (abdominal pumping)

• contraction of abdominal muscles, which changes pressure in the body, causing air to move in/out

• So maintains concentration gradient for diffusion

How is an insects tracheal system adapted for gas exchange (Fluid in end of tracheoles)

• fluid is drawn into tissues by osmosis during exercise (lactate produced in anaerobic respiration lowers water potential of cells)

• As fluid is removed air fills tracheoles

• So rate of diffusion increases as diffusion is faster through air

Explain how terrestrial insects limit water loss

• thick waxy cuticle/ exoskeleton. Increases diffusion distance so less water loss by evaporation

• Spiracles can open to allow gas exchange and close to reduce water loss by evaporation

• Hairs around spiracles. Trap moist air, reducing water potential gradient so less water loss by evaporation