Gaseous Exchange In Insects

Question 1

Why do insects need a different way of exchanging gases?

Answer 1

they have relatively high oxygen requirements

their exoskeleton is impermeable to gases so none can take place

they need a different way to deliver oxygen directly to cells and to remove carbon dioxide in the same way

Question 2

How do gases enter an insect?

Answer 2

along the thorax and abdomen most insects have small openings known as spiracles

gases are exchanged through here the spiracles lead the the tracheAE

Question 3

What are the function of the sphincter on the spiracles?

Answer 3

minimise water loss

Question 4

When does a insect close its sphincters?

Answer 4

when inactive or oxygen demands are low, spiracles will be closed most of the time

they open when carbon dioxide levels are too high or when oxygen demand is increased

Question 5

What are the features of the trachea?

Answer 5

the tubes are lined with chitin which keeps them open if they are pressed

chitin is relatively impermeable to gases 1mm in diameter

Question 6

What does the trachea lead into?

Answer 6

the trachea branch smaller and smaller into tracheoles (0.7 micrometres)

each tracheole is a single, greatly elongated cell that is permeable to gases

they spread through the tissue of the insect, this is where most gaseous exchange takes place

Question 7

How do insects increase the surface area for gaseous exchange?

Answer 7

many tracheoles give a very large surface area

lactic acid build up on tissues results in water moving out the tracheoles and exposes more surface area for gas exchange when the O2 demand is high

Question 8

What is mechanical ventilation of the tracheal system?

Answer 8

muscular pumping movements in the thorax/abdomen changes the pressure in the trachea and tracheoles and air is forced in or out

Question 9

What is the function of collapsible enlarged trachea?

Answer 9

act as air resivoirs used to increase the amount of air moved through the gas exchange system

inflated and deflated by the ventilating movements of the thorax and abdomen

Question 10

What problems do insects have to overcome to gain oxygen?

Answer 10

tough, impermeable external exoskeleton very active - high metabolic demands blood doesn’t contain oxygen carrying pigment

Question 11

What are the states of gas exchange

Answer 11

insects have three states of gas exchange

• • open,
    
    • release built up CO2
    • , pumping of abdomen maximises gas exchange
• closed
  
  • no gas moves
  • CO2 held in bodu
• or fluttering
  
  • spiracles rapidly close and open
  • moves oxygen towards the trachea
  • minimises water loss
    *

Question 12

What is the fluid responsible for gaseous exchange in insects?

Answer 12

tracheal fluid