1. The need for an exchange system in multicellular organisms
Why doesn’t an amoeba need lungs or gills?
Amoeba

2. Practical – the effect of surface area on efficiency of exchange surfaces
You need – tile, scalpel, 3 small beakers, block of stained agar, stop clock
Use scalpel to cut block into 3 equally sized pieces (use a ruler)
block 1 stays complete,
block 2 cut into 4 equally sized pieces,
block 3 cut into 8 pieces (use a ruler)
Put each set of blocks into each of the 3 beakers with 10cm3 hydrochloric acid - start the stop clock immediately
Measure width, length and height of 1 block (mm)
calculate the total surface area for the smaller blocks,
(S.A .of 1 block x number of blocks)= total S.A.
While you are waiting –
Draw a suitable table to record the side measurements of the blocks
Describe relationship shown by your graph

3. Block
Width
(mm)
Length
Height
Surface area
(mm2)
Number of blocks
Total surface area of blocks (mm2)
Time taken for pink colour to disappear
(s) 1 2 3

4. Make a list of at least 5 errors in the construction of this table
Block
Width
Length
Height
(mm)
Surface area
Number of blocks
Total surface area of blocks
Time taken for pink colour to disappear 1
1cm
2cm 2
16cm2
1min 34sec
1.0 10 20
1min 10s 3
0.5
7.00 4 28
54.05s

5. Block
Width
(mm)
Length
Height
Surface area
(mm2)
Number of blocks
Total surface area of blocks (mm2)
Time taken for pink colour to disappear
(s) 1 10 20
1600 94 2 5
700 4
2800 70 3
400 8
3200 54

6. Why doesn’t an amoeba need lungs or gills?
An amoeba is single celled it therefore has ……
Multicellular organisms need lungs or gills because …..

7. What are the main materials that cells need to exchange with their surroundings?
Oxygen for ……
Glucose for …….
Water
Minerals for …….
Waste product removal eg ……..
Metabolism =

8. Surface area : Volume ratio
Which has the largest SA:V?

9. Calculating surface area : Volume ratio
Smaller animals have higher SA:V ratios V
Task:
Complete worksheet on SA:V ratio relationship

10. An Exchange System that Meets an Organisms Needs
Surface area to Volume Ratio
Activity/ energy requirements
Environment
Transport Solutions
Bacteria
Insect
Fish
Plant
Polar bear

11. Length of side cm
Surface area
cm2
Volume
cm3
Surface area:Volume 1 6
6.0 2 24 8
3.0 3 54 27
2.0 4 96 64
1.5 5
150
125
1.2 10
600
1000
0.6

13. Fungal hyphae absorb …..
Plant root hairs absorb…..

14. Exchange surfaces:
What do all exchange surfaces have in common?

15. Plenary question
Q1; Jan 2007

16. Plenary question
Q1; Jan 2007

17. Plenary question
Q1; Jan 2007