2. Module 3 Exchange and transport
7. Exchange surfaces
7.4 Ventilation and gas exchange in insects

3. Learning Objectives Success Criteria
Demonstrate knowledge, understanding and application of the mechanisms of ventilation and gas exchange in insects
Identify the insect tracheal system as the site of gaseous exchange (Grade E - D)
Understand the mechanisms of ventilation and adaptations of gas exchange in insects
(Grade C –B)
Apply understanding to the examination and drawing of a insect trachea
(Grade B – A)
FISH DISSECTION?

4. Starter What challenges do insects face living on the land?
What adaptations do they have to ensure their survival?

5. Insects are adapted to conserve water
Small Surface area :Volume ratio to minimise water loss from the body surface
Waterproof coverings
e.g. In insects the exoskeleton is covered with a waterproof cuticle (impossible for gases to diffuse)
Insects have developed a breathing system of tubes that carry oxygen directly to the tissues/organs of body
Spiracles that open and close by sphincters

6. Insects are adapted for gas exchange Insect Tracheal System
Tracheal tubes run from the body surface into the tissues
Transport gases directly between the external environment and the body cells

7. Anatomy of insect gas exchange system
The thorax and abdomen) have a pair of lip-like openings called spiracles
Tracheal tubes connected to each spiracle branch into a series of tracheoles
Tracheoles repeatedly divide until their numerous microscopic ends penetrate into individual body cells
Towards the end of the tracheoles there is tracheal fluid which limits the penetration of air for diffusion

8. Adaptations of insects for gas exchange
Oxygen demand increases = spiracles open
Trachea lined with chitin (impermeable to gases) = keeps them open even when bent
Tracheoles = permeable to gases ,
= very small size, so can spread between cells
= large surface area
= moisture on walls so oxygen diffuses to cells
When oxygen demands are high, lactic acid builds up in tissues, so water moves out of tracheoles by osmosis, exposing more SA for gas exchange
Complete worksheet gas exchange

9. Insects with high energy demands
For example larger beetles, locusts and grass hoppers
Collapsible enlarged trachea or air sacs
Act as air reservoirs used to increase the amount of air moved through the gas exchange system by ventilating movements of the thorax and abdomen
Ventilation by rhythmic abdominal movements
Further speeds up the exchange of respiratory gases by generating mass movements of air in and out of the tracheal tubes by the changing pressure in the trachea and tracheoles by the movement of muscles

10. Histology of exchange surfaces
Look at slides of exchange surfaces for
Alveoli
Gills
Trachea in insects
Make a labelled diagram using skills previously learned

11. Homework
Complete exam questions

12. Plenary
Compile a table to compare the gas exchange systems of a human, an insects and a bony fish
What structures of the gas exchange systems allow the features below?
human
fish
insect
Large surface area
Short diffusion path
Steep concentration gradient