Gas Exchange In Insects

Question 1

How does air enter and leave the insect?

Answer 1

Air enters and leaves through small openings along the thorax and abdomen called spiracles.

Question 2

How are spiracles opened and closed?

Answer 2

By sphincters.

Question 3

Why are spiracles kept closed as much as possible?

Answer 3

To minimise water loss from the insect.

Question 4

What is the system called in which gas is exchanged in an insect?

Answer 4

The Tracheal System

Question 5

What happens to the spiracles when oxygen demands are low?

Answer 5

Spiracles are closed.

Question 6

What happens to the spiracles when oxygen demands are high?

Answer 6

More spiracles are opened up

Question 7

What is the tracheae and where is it located?

Answer 7

It is the largest tube in the insects respiratory system and it is located above the spiracles

Question 8

What are the tracheae tubes lined with?

What does this do?

Answer 8

Chitin spirals.

Keeps them open. Also it makes them impermeable to gas exchange so NO gas exchange occurs in tracheae.

Question 9

What are the narrow tubes called that the tracheae divide into?

Answer 9

Tracheoles. They are super tiny (0.6-0.8 micrometers)

Question 10

What is a tracheole?

Answer 10

One elongated cell which has no chitin lining so gaseous exchange can occur. These are also moist.

Question 11

How are gas and nutrients exchanged to every cell?

Answer 11

The really thin tracheole tubes go through and to every cell and gases are exchanged by diffusion.

Question 12

Insects have numerous tracheoles. Why?

Answer 12

For an increased surface area so more gas is exchanged.

Question 13

Where is the tracheal fluid in an insect?

Answer 13

At the ends of the tracheoles.

Oxygen dissolves in this.

Question 14

When an insect flies, what is there a build up of?
What does this do to the water potential in the tissues?
What does this lead to?
What does this do to the surface area of the tracheoles?

Answer 14

Lactic acid builds up in the tissues.

Lowers the water potential in the tissues.

Movement of water from tracheal fluid to the tissues by osmosis, down a concentration gradient.

This increases surface area of tracheoles for more gas exchange to occur which is needed due to the higher demand of flying.

Question 15

What three ways reduce water loss in insects?

Answer 15

A small surface area to volume ratio.
A waxy cuticle on the outside of the exoskeleton.
Spiracles close and open according to the environment.

Question 16

What do large insects have a high demand of?

Answer 16

Oxygen and energy.

Question 17

What two other ways do large insects exchange gases to help keep up with the demands?

Answer 17

1- mechanical ventilation

2- collapsible enlarged tracheae.

Question 18

Describe how mechanical ventilation of the tracheal system works to keep up with high oxygen demands in insects.

Answer 18

Pumping movements of the abdomen and thorax force air into the system as the pressure is increased and decreased inside the insect.

Question 19

Describe how collapsible enlarged tracheae works to keep up with high oxygen demands in insects.

Answer 19

The tracheae or air sacs are inflated and deflated by pumping movements of the abdomen. This increases the amount of air moved through the system by increasing the volume of the body.

Question 20

Show the path of air as it moves into the insect to each cell.

Answer 20

Spiracles
Tracheae
Tracheoles
Tracheal fluid
Tissues and cells

Question 21

Why do insects have relatively high oxygen requirements?

Answer 21

Insects are land-dwelling animals and active creatures

Question 22

Why do insects need a gaseous exchange system?

Answer 22

They have high oxygen requirements.
No gas can exchange directly through the exoskeleton.
There’s no blood pigment to carry oxygen.

Question 23

What is the tracheal fluid?

Answer 23

A fluid at the end of tracheoles, which limits the penetration of air for diffusion.

Question 24

What does DGC stand for?

Answer 24

Discontinuous Gas Exchange Cycles

Question 25

What happens in DGC?

Answer 25

Where the spiracles have three states; closed, open and fluttering.

Question 26

What happens when the spiracles are closed?

Answer 26

No gas moves in/out.
Oxygen moves into cells from trachea.
Carbon dioxide moves into the body fluids.
Held closed by a process called buffering.

Question 27

What happens when the spiracles are fluttering?

Answer 27

Spiracles open and close rapidly.
Moves fresh air into the trachea to renew oxygen supply.
This minimises water loss

Question 28

When do the spiracles open?

Answer 28

When carbon dioxide levels are high spiricles open wide to remove it.

Question 29

What three ways allow an insect to conserve water?

Answer 29

Waxy cuticle on the outside of the exoskeleton.
Spiracles open and close.
Small surface area to volume ratio.