Ventilation in insects

Question 1

What is the exoskeleton? Can gases be exchanged through the exoskeleton?

Answer 1

External skeleton of insects.

Little to no gas exchange can take place through it

Question 2

What are spiracles?

Answer 2

Small openings along the thorax and abdomen of insects

Question 3

What is lost when air moves through spiracles?

Answer 3

Water

Question 4

What closes and opens spiracles?

Answer 4

Sphincters

Question 5

Why are spiracle sphincters kept closed as much as possible?

Answer 5

To minimise water loss

Question 6

When will spiracles be closed?

Answer 6

When insect is inactive and has low oxygen demands

Question 7

When will spiracles be open?

Answer 7

When insect is active and has high oxygen demands and high CO2 levels

Question 8

What leads away from the spiracles?

Answer 8

Tracheae

Question 9

What is the structure of tracheae? What is their function?

Answer 9

Largest tubes of insect respiratory system, 1mm in diameter.

Carry air into body.

Question 10

Where can tracheae be found?

Answer 10

Inside + along the insect body

Question 11

What are tracheae lined with?

Answer 11

Chitin

Question 12

What is the function of chitin?

Answer 12

Keep tracheae open when they’re bent

Question 13

Why does little gas exchange occur in the tracheae?

Answer 13

It’s made up of chitin, which is an impermeable gas

Question 14

What do tracheae branch into?

Answer 14

Tracheoles, 0.6-0.8 microns

Question 15

What is the structure of tracheoles?

Answer 15

Single, elongated cell with no chitin lining - freely permeable

Question 16

Where does most of the gas exchange in insects occur?

Answer 16

In tracheoles

Question 17

In most insects, how does air move through their body?

Answer 17

By diffusion, along tracheae and tracheoles

Question 18

Why do tracheoles enable efficient gas exchange?

Answer 18

Provide a large SA

Question 19

How does oxygen enter insect cells?

Answer 19

Oxygen dissolves in moisture on tracheole walls + diffuses into surrounding cells

Question 20

What is tracheal fluid?

Answer 20

Fluid found at end of tracheoles

Question 21

What is the function of tracheal fluid?

Answer 21

Helps control SA for gas exchange and water loss

Question 22

What happens when oxygen demands in an insect build up?

Answer 22

Lactic acid builds up + water moves out of tracheoles by osmosis

Question 23

What system supplies all insect oxygen needs?

Answer 23

Tracheal system

Question 24

What is the extent of gas exchange in insects controlled by?

Answer 24

Spiracles opening and closing

Question 25

What are the 2 alternative methods larger insects have to increase gas exchange?

Answer 25

1. Mechanical ventilation of tracheal system

2. Collapsible enlarged trachea/air sacs, which act as air reservoirs

Question 26

How does mechanical ventilation of the tracheal system increase gas exchange in larger insects?

Answer 26

• Air is actively pumped -> tracheal system by muscular pumping movements of thorax + abdomen
• These movements change volume of body + change pressure in tracheoles and tracheae
• Air is drawn into tracheae and tracheoles / forced out as pressure changes

Question 27

How do collapsible enlarged tracheae/air sacs, which act as air reservoirs, act as an alternative method of increasing gas exchange in larger insects?

Answer 27

The enlarged tracheae increase amount of air moving through gas exchange system.
They’re usually inflated + deflated by ventilating movements of thorax + abdomen