3.2.1 gas exchange (insects)

Explain the structure of terrestrial insects

• an exoskeleton made of hard fibrous material for protection

• A lipid layer to prevent water loss

What do terrestrial insects have instead of lungs

A tracheal system

How do insects limit water loss

1. Small SA:V, reducing where water can evaporate from

2. Waterproof exoskeleton

3. Spiracles can open and close

What 3 things make up the insects tracheal system

1. Spiracles

2. Trachea

3. Tracheoles

What are the spiracles

• round, valve like openings, running along the abdomen

• This is where oxygen and carbon dioxide enter/ leave

• The trachea attach to these openings

What are the trachea

• network of internal tubes

• Have rings inside them to strengthen the tubes and to keep them open

What are the tracheoles

• the trachea branched into smaller tubes

• Extend throughout all tissues to deliver oxygen to respiring cells

3 methods of moving gases in terrestrial insects

1. Diffusion

2. Mass transport

3. Pressure changes

How do gases exchange by diffusion in terrestrial insects

• when cells respire they use oxygen and produce carbon dioxide

• This creates a concentration gradient from the tracheoles to the atmosphere

How do gases exchange by mass transport in terrestrial insects

• an insect contracts and relaxes their abdominal muscles

• This allows gases to move in mass

How do gases exchange by pressure changes in terrestrial insects

• when the insect is in flight, muscle cells start to respire aerobically to produce lactate

• This lower water potential so water moves out of tracheoles and into cells by osmosis

• This decreases volume in the tracheoles, so air is drawn in

How are terrestrial insects adapted for efficient diffusion

1. Large number of branched tracheoles — large SA

2. Tracheoles walls are thin + short distance between spiracles and tracheoles — short diffusion pathway

3. Use of oxygen and production of carbon dioxide — steep diffusion pathway