Gaseous Exchange Systems Of Other Organisms

Question 1

What are spiracles?

Answer 1

Small openings along the thorax and abdomen of most insects
Air enters and leaves the system through them
Water can also be lost through them (wants to be minimised)

Question 2

What are sphincters?

Answer 2

They open and close spiracles to minimise water loss from insects

Question 3

Describe the insect respiratory system

Answer 3

1. Air enters through spiracles which are controlled by sphincters
2. Air enters into the tracheae which carries it into the body and along the body
3. The tracheae branch to form narrower tubes until they divide into the tracheoles which run between individual cells
4. Gaseous exchange takes place here between the air and the respiring cells

Question 4

Describe the tracheae?

Answer 4

Largest tubes in the insect respiratory system - up to 1mm diameter
Lined by spirals of chitin - keeps them open if they are bent or pressed, relatively impermeable so little gaseous exchange takes place here

Question 5

Describe the tracheoles

Answer 5

Each tracheole is a single elongated cell
No chitin lining so completely permeable to gases

Question 6

How does air move through the insect respiratory system?

Answer 6

Moves along the tracheae by diffusion
Oxygen dissolves into moisture of the walls of the tracheoles and diffuses into surrounding cells

Question 7

What happens when an oxygen demand builds up in the insect respiratory system?

Answer 7

Towards the end of the tracheoles there is tracheal fluid which limits the penetration of oxygen
When the oxygen demands build up lactic acid builds up in the tissues
This causes water moving out of the tracheoles by osmosis
More surface area is exposed for gas exchange

Question 8

What are alternative methods of increasing the level of gaseous exchange for insects with very high energy demands?

Answer 8

1. Mechanical ventilation of the tracheal system - air actively pumped by abdomen and thorax as the movements change the volume and pressure of the tracheae and tracheoles
2. Collapsible enlarges tracheae or air sacs - act as air reservoirs, can be used to increase the amount of air moved through the system