Module 3: Ventilation and Gas Exchange in bony fish and insects

Question 1

Do insects have an open or closed circulatory system?
What does this mean regarding blood and the function of body fluid?

Answer 1

they have an open system
so blood does not transport oxygen , so body fluid acts as blood and tissue fluid

Question 2

Is circulation fast/slow in insects and what is it affected by?

Answer 2

circulation is slow and is affected by body movements

Question 3

Do insects have a tough/soft exoskeleton ?
What effect does this have on gas exchange?

Answer 3

they have a tough exoskeleton
so little to no gas exchange can happen through/across it

Question 4

Insects have an air filled tracheal system , describe the process of this system
5 points
What does this system do fundamentally?

Answer 4

it supplies air directly to all the respiring tissues
1)air enters the system via a pore in a spiracle
2)the air is transported into the body through a series of tubes called tracheae
3)these divide into smaller tubes called tracheoles
4)gas exchange occurs between the air in the tracheoles and the tracheal fluid
5)some exchange also occurs across the thin tracheole walls

Question 5

Describe the structure of the tracheoles…
(the end of them)

Answer 5

the ends are open and filled with fluid called tracheal fluid

Question 6

How is the tracheal system adapted to the high oxygen demand of insects?
3 points

Answer 6

-when tissues are active , tracheal fluid can be withdrawn into the body fluid
-this increases the surface area of the tracheole wall exposed to air
-this means more oxygen can be absorbed

Question 7

Describe one way in which larger insects move their bodies for ventilation…
3 points

Answer 7

-sections of the tracheal system expand as they have flexible walls
-so they act as air sacs which can be squeezed by action of the flight muscles
-repetitive expansion/contraction of these sacs ventilate the system

Question 8

Describe a second way that larger insects move their bodies for ventilation…
3 points

Answer 8

-movements of the wings can alter the volume of their thorax
-a decrease in volume puts the system under pressure and air is pushed out
-an increase in volume decreases the pressure within the system which forces air into the system from outside

Question 9

Describe a final way that larger insects move their bodies for ventilation…
4 points

Answer 9

-some insects (eg locusts) can alter the volume of their abdomen by specialised breathing movements
-these movements are coordinated with opening and closing valves in the spiracles
-as the abdomen expands , spiracles at front of body open and air enters system
-as volume of abdomen decreases , spiracles at rear end open and air leaves the system