1. Exchanging materials – the lungs
p.220

2. Requirements
Lung/alveolus diagrams
Lungs to dissect

3. Outcomes Most students should be able to:
describe the features of exchange surfaces that make them effective
describe the function of the alveoli
explain how the alveoli are adapted for the efficient exchange of gases.
Some students should also be able to:
evaluate the importance of adaptations which give increased surface area to the effectiveness of gas exchange.

4. Objectives Students should learn:
that many organ systems are specialised for exchanging materials
that exchange surfaces in humans and other organisms are adapted to maximise effectiveness
that the lungs are especially adapted for the exchange of gases
that the alveoli provide a large surface area over which gases can readily diffuse into and out of the blood.

5. Specification
Many organ systems are specialised for exchanging materials. The effectiveness of an exchange surface is increased by:
– having a large surface area.
– being thin, to provide a short diffusion path.
– (in animals) having an efficient blood supply.
– (in animals, for gaseous exchange) being ventilated. [B3.1.1 h)]
Gas and solute exchange surfaces in humans and other organisms are adapted to maximise effectiveness. [B3.1.1 i)]
The size and complexity of an organism increases the difficulty of exchanging materials. [B3.1.1 j)]
In humans:
– the surface area of the lungs is increased by the alveoli. [B3.1.1 k)]

6. Workbook P

7. Gas exchange mechanisms choose from body skin /gills /lungs /mesophyll cells
Letter
Organism
How it exchanges Oxygen and carbon dioxide A
Fish B
Frog C
Tadpole D
Amoeba E
Plant F
Locust G
Snail H
Worm

8. For each letter record how the organism exchanges its gasesB C A
For each letter record how the
organism exchanges its gases F D E H G

9. Question
What do you notice about the difficulty of gas exchange in a more complex organism?
It is more difficult/requires better adapted exchange surface

10. Adaptations of a gas exchange surface
Make a list of 4
Learn them!!

11. lung
intestine
Person is ~1.5 m tall and ~0.08 m3.
Skin is ~2 m2, so person as a box is ~1 m2 × 0.1 m thick.
Lung is ~100 m2 and ~0.01 m3, so lung as a sheet is ~7 m2 × ~10-4 m thick.
Intestine is ~300 m2 and ~0.01 m3, so intestine as a sheet is (~12 m2 x ~10-4m thick.

12. The human breathing system
How an alveolus is adapted for gas exchange

13. Alveolus on next slide and in book

14. Label your diagram carefully
B3 1.2 gas exchange in the lungs
Label your diagram carefully
Use page 224 in text book to help you 1 2 7 3 8 9 4 10 11 5 6

17. Q2 and 3 p.221
2. Gas exchange is the exchange of oxygen and carbon dioxide in the lungs in humans. Vital to supply oxygen to the red cells in the blood which is transported to tissues for respiration, and to get rid of the waste product of carbon dioxide from respiration carried back to lungs by the plasma in the blood

18. Q3 Many alveoli combined have a large surface area for gas exchange
Alveoli have a rich blood supply maintaining the concentration gradients of oxygen and carbon dioxide
Ventilation refreshes the gases in the alveoli maintaining the concentration gradients
The alveolar and capillary cells are flattened so there is a short diffusion pathway for the gases

19. Lung dissection
Or video if you wish