Bio Lab Essay

1217 WordsDec 11, 20115 Pages
TEACHERS INSTRUCTIONS: To observe the rate of diffusion in three different sizes of agar gel with respect to surface area volume ratio. 1. Cut 3 cubes each of side 1cm, 2cm and 3cm from the slab of agar gel provided 2. Measure 75cm3 of sodium hydroxide solution in a beaker 3. Take one cube of agar gel of side 1cm and immerse in the measured sodium hydroxide solution 4. Cover the beaker with a Petri dish and start the stopwatch. 5. Remove the agar cube from sodium hydroxide solution and dry it with a tissue paper. 6. Place the same agar cube on a clean white tile and using a sharp knife cut it into half. 7. Using a cm scale measure the distance of colour change from the edge of the cube. 8. Repeat this experiment two more times for accuracy. 9. Using sodium hydroxide solution to the experiment with cubes of sides 2 cm and 3 cm. Aim: To investigate the effect of the size of the cube on the extent to which the agar gel cube has absorbed the sodium hydroxide solution. Background Information: The ratio between the surface area and volume of cells and organisms has an enormous impact on their biology. For example, many aquatic microorganisms have increased surface area to increase their drag in the water. This reduces their rate of sink and allows them to remain near the surface with less energy expenditure. Humans and other large animals cannot rely on diffusion for absorption and rejection of respiratory gases, for their whole body; however, animals such as flatworms and leeches can, as they have more surface area per unit volume. For similar reasons, surface to volume ratio places a maximum limit on the size of a cell. An increased surface area to volume ratio also means increased exposure to the environment. The many tentacles of jellyfish and anemones provide increased surface area for the acquisition of food. Greater surface area allows more of

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