02A_Agar+Experiment

__**BIOLOGY AGAR REPORT ** To explore the relationship between surface area to volume ration and rate of exchanging materials. __**Hypothesis: **__ The larger the surface area to volume ratio, the higher the rate of conductivity. This is because a larger ratio would indicate a larger number of sides. The higher the number of sides, the more efficiently the cell can gather nutrients and import/export various materials. __**Method: **__ Step 1: Use a scalpel to cut one of the agar cubes on the white tile till it is 2 x 2 x 2cm. Use ruler to measure the correct lengths before cutting. (Note: DO NOT use forceps to grip agar cubes as they will “break”)
 * Aim: **__

Step 2: Use the scalpel to cut the second agar cube into 8 smaller cubes of sides 1 x 1 x 1cm on a white tile. Use a ruler to measure the correct lengths before cutting.

Step 3: Use the scalpel to cut the third agar cube into 64 smaller cubes of sides 0.5 x 0.5 x 0.5cm on a white tile. Use a ruler to measure the correct lengths before cutting.

Step 4: Fill a beaker with 200ml of tap water and place the conductivity probe which is connected to the data logger in the water.

Step 5: Place the largest single agar block (2 x 2 x 2cm) into the water and click the “run” icon on the data logger to start recording data. Start the stopwatch concurrently.

Step 6: Stir the water with the glass rod continuously and gently, being careful not to hit the probe too much.

Step 7: After two minutes, stop the data logger. Record the change in reading (seen on the data logger) after two minutes.

Step 8: Take note of the graph and read the highest conductivity in the period of the two minutes.

Step 9: Repeat steps 4-8 for the 1 x 1 x 1cm cubes and the 0.5 x 0.5 x 0.5cm cubes and record the results in a table __**Results: **__ Results for the 0.5 x 0.5 x 0.5cm agar cubes
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Time(s) || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Conductivity I/O-1(mS) ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">0 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">0.63 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">10 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">2.57 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">20 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">1.7 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">30 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">1.8 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">40 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">1.89 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">50 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">2.25 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">60 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">5.88 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">70 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">5.5 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">80 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">7.65 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">90 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">8.09 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">100 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">7.85 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">110 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">8.16 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">120 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">8.04 ||

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Results for the 1 x 1 x 1cm agar cubes
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Time(s) || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Conductivity I/O-1(mS) ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">0 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">0.41 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">10 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">0.76 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">20 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">0.97 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">30 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">1.04 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">40 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">1.1 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">50 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">1.19 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">60 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">1.27 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">70 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">1.37 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">80 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">1.39 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">90 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">1.45 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">100 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">1.5 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">110 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">1.58 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">120 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">1.58 ||

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Results for the 2 x 2 x 2cm cubes **<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Comparison of rate of conductivity change for different surface area to volume rations **
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Time(s) || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Conductivity I/O-1(mS) ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">0 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">0.15 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">10 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">0.14 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">20 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">0.35 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">30 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">0.46 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">40 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">0.48 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">50 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">0.51 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">60 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">0.54 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">70 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">0.57 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">80 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">0.61 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">90 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">0.64 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">100 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">0.67 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">110 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">0.71 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">120 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">0.72 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">No. of pieces of agar cubes || **<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Length (cm) ** || **<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Surface area (cm2) ** || **<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Volume (cm3) ** || **<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Surface area to volume ratio ** || **<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Rate of conductivity change ** ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">1 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">2 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">24 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">8 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">3 : 1 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">0.72 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">8 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">1 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">6 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">8 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">3: 4 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">1.58 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">64 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">0.5 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">1.5 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">8 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">1.5 : 8 || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">8.16 ||

**<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Graph of the conductivity of the 0.5 x 0.5 x 0.5cm agar cubes **

**<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Graph of the conductivity of the 1 x 1 x 1cm agar cubes ** **<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Graph of the conductivity of the 2 x 2 x 2cm agar cube <span style="font-family: Helvetica,helvetica,sans-serif;"> ** **<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Data Analysis ** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Conductivity is the diffusion of ions through membranes, in this case the exchange of materials between the agar cells. The 0.5 x 0.5 x 0.5 cm agar cubes had the highest rate of conductivity, followed by the 1 x 1 x 1cm cubes, then the 2 x 2 x 2cm cubes (as seen in the graphs and tables). Also, the 0.5 x 0.5 x 0.5 cm agar cubes have the highest number of sides and the highest surface area to volume ratio, followed by the 1 x 1 x 1cm cubes, then the 2 x 2 x 2cm cubes (as seen in the table). This is probably because the higher the number of exposed sides, the higher the rate of conductivity. The exposed surfaces allow materials to be exported/imported and exchanged more efficiently, therefore explaining why the 0.5 x 0.5 x 0.5 cm agar cubes had the highest rate of conductivity-- There was the most number of 0.5 x 0.5 x 0.5cm agar cubes and hence the most number of sides, allowing efficient diffusion amongst cells, therefore having the highest rate of conductivity.

__**<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Discussion Questions **__ <span style="font-family: Helvetica,helvetica,sans-serif; font-size: 11px; line-height: normal;">**1. What precautions did you take** in **this experiment? -Forceps were not used to grip the agar cubes as they would cause the cubes to “break” -The stopwatch was started concurrently as the data logger was set to “run” so that the time recorded could be accurate. 2. **What can you infer from the results above? The higher the number of exposed sides, the higher the rate of conductivity. The exposed surfaces allow materials to be exported/imported and exchanged more efficiently.

3. **What do the graphs reveal to you about the rate of diffusion and the surface area of the agar? The conductivity was the highest in the graph of the 0.5 x 0.5 x 0.5cm cubes, followed by the 1 x 1 x 1cm cubes, then the 2 x 2 x 2cm cubes, indicating that the rate of diffusion got increasingly larger as the size of the cubes decreased. This was because the cubes of varying sizes were derived from blocks of agar of the same size, therefore causing the number of cubes derived from the agar blocks to be different. The smaller the cubes, the more could be derived from the same agar block, allowing for more exposed surfaces, causing the rate of diffusion to be higher.

4. **Compare this experiment with the one that you did in Lower Secondary where coloured agars were soaked in acid. Which do you think is more accurate? This one is more accurate. This is because in this experiment, we made use of the data logger and the conductivity probe to obtain the results. The machines would provide more accurate results as they are more much more sensitive and less prone to errors (eg. human error).

5. **How do you relate this to the shape of simple (eg. earthworm) to complex (eg. tiger) living organisms? The transport systems in complex organisms must be more developed and efficient as the products (food, water, waste etc.) have to be transported a further distance than in that of a simple organism.

6. **Examine the agar cells below and work out the surfaced area to volume ratio of each cell. Which is most efficient and which is least? <span style="font-family: Arial,helvetica,sans-serif; font-weight: normal;">The most efficient agar cells will be the 64 cubes with lengths of 0.5cm and a surface area to volume ratio of 1:16 because it has the smallest surfaced area to volume ratio. The least efficient one would then be the agar cube with the length of 2cm and a surface area to volume ratio of 3:1 because it has the largest surface area to volume ratio.