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

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

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

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

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

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

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 =

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

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

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

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

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

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

Plenary question Q1; Jan 2007

Plenary question Q1; Jan 2007

Plenary question Q1; Jan 2007