Investigating Photosynthesis Using Algal Balls

Transcription

1 Investigating Photosynthesis Using Algal Balls Safety Notes: There are no harmful chemicals in this investigation if handled appropriately Apparatus Beaker (100 or 250 ml) with ml calcium chloride (1.5% w/v) Clamp and clamp stand Small bottle with lid Nannochloropsis algal suspension Sodium alginate solution Syringe Distilled water Strainer Pipettes 1. You will be given a beaker with algae settled at the bottom. Carefully pipette off the water. DO NOT bubble air into the beaker as this may disturb the algae. 2. Pipette 3mls of the concentrated green algae at the bottom of the beaker into a plastic bottle. 3. Pipette 3mls of the sodium alginate into the plastic bottle with the algae. Place the lid onto the bottle. 4. Gently mix the algae and alginate together by tipping your bijou bottle back and forward. Try not to be too vigorous as this may trap air bubbles in the mixture. 5. Place a syringe vertically in the clamp stand. 6. Pour approx. 50ml calcium chloride in a beaker. Place the beaker directly underneath the syringe. 7. Pour your algae and alginate mixture into the syringe. The mixture will drip slowly into the beaker of calcium chloride. 8. When all the mixture has all dripped through, leave the algal balls in the beaker of calcium chloride for 3-5 minutes. They will become solid. 9. Tip the algal balls into a tea strainer and rinse with distilled water. 10. Place the algal balls in a beaker of fresh distilled water until you need them for the investigation.

2 Introduction Baseline Investigation The Effects of Light on Photosynthesis in Algal Balls You are going to use the algal balls you just made to answer the question Does photosynthesis need light to proceed? 1. Place the same number of algal balls (rinsed with distilled water) into two plastic bottles. 2. Fill each bottle full with 3mL of red indicator solution (1X hydrocarbonate solution) using a pipette and replace lid 3. Fill a third empty bijou bottle with the indicator solution (this is a control) 4. Wrap aluminium foil around one of the bottles containing algal balls and indicator so that no light can get into the bottle. 5. Place all three bottles the same distance from the light source. Leave for 20 minutes. 6. Prepare a results table to record the colour and ph in each bottle afterwards Bottle contents 1 control (indicator only) 2 algal balls + indicator no covering on the bottle 3 algal balls + indicator + aluminium foil Indicator colour at the start Indicator colour after 20 mins 1. What process in plants uses carbon dioxide? 2. In which of your bottles will this process be taking place? 3. What process in living things (including plants) produces carbon dioxide? 4. In which of your bottles will this process be taking place? 5. Why have we set up a bottle without the algal balls? 6. What are your predictions? Explain using the terms photosynthesis and respiration. After you have collected your results, compare them to other groups near you and say whether they fit your predictions. Try to explain any anomalies (odd results). Can you answer the question that you were investigating? The Next Step: Based on this baseline investigation, determine another variable to test using this method. Design the experiment by completing the inquiry proposal form fro approval. Your final

3 product will be a mini-poster presented in a Gallery Walk. This is due on.

4 Introduction Investigation 2a: Light Intensity (distance from lamp) You will either have made or been given some algal balls. You are going to use them to answer the question Does light intensity affect the rate of photosynthesis? 1. Place the same number of algal balls (rinsed with distilled water) into 5-6 bijou bottles. 2. Fill each bottle full with indicator solution using a pipette and replace the lid 3. Place the bottles equal distances apart along a 30cm ruler 4. Place a switched off lamp at one end of the ruler facing the bottles 5. Switch on the lamp and set your timer for the time you have chosen 6. When the time is up, record the colour and /or ph in each tube prepare a results table similar to the one below Distance from the lamp (cm) Indicator colour at the start or ph value at the start Indicator colour after 30 mins or ph value after 30 mins 1. What process in plants uses carbon dioxide? 2. In which of your bottles will this process be taking place most quickly? - explain 3. What process in living things (including plants) produces carbon dioxide? 4. In which of your bottles will this process be taking place? 5. What are your overall predictions? explain using the terms photosynthesis and respiration After you have collected your results, compare them to other groups near you and say whether they fit your predictions. Try to explain any anomalies (odd results). Can you answer the question that you were investigating? Questions on the method Was this a fair test? What were your variables (dependent, independent, control)? Can you think of a method that would have enabled you to collect more reliable data?

5 Investigation 2b: Light Intensity (neutral density filters) Introduction You will either have made or been given some algal balls. You are going to use them to answer the question, Does light intensity affect the rate of photosynthesis? 1. Wrap one of the three different neutral density filters around three different bijou bottles 2. Check there are no gaps then fix the filters into place with sticky tape 3. Leave a fourth bottle with no filter, and a fifth bottle covered in black paper 4. Place the same number of balls into each of the small bottles. 5. Fill each bottle full with hydrogen carbonate indicator solution and replace the lid 6. Place the bottles equal distances away from a switched off light source, making sure the sticky tape faces away from the light 7. Once they are all in place, switch on the light and leave for 30 mins 8. When the time is up, remove the filters and record the colour and /or ph in each tube Filter on bottle % light transmitted into the bottle Colour / ph value of indicator after x mins 0.00 ND (no filter) ND ND ND ND (black paper) 0 Note: When light hits a neutral density (ND) filter, some is absorbed and some is allowed through (transmitted) regardless of the colour of the light. Some ND filters transmit more light than others. 1. Which of your algal balls will be getting the most light? Which will be getting the least? 2. What process in plants uses carbon dioxide? 3. In which of your bottles will this process be taking place most quickly? - explain 4. What process in living things (including plants) produces carbon dioxide? 5. In which of your bottles will this process be taking place? 6. What are your overall predictions? explain using the terms photosynthesis and respiration After you have collected your results, compare them to other groups near you and say whether they fit your predictions. Try to explain any anomalies (odd results). Can you answer the question that you were investigating?

6 Investigation 3: Compensation point between photosynthesis and respiration Introduction You will either have made or been given some algal balls. You are going to use them to investigate the question: At what light intensity will the algae reach their compensation point? Respiration produces CO 2 and photosynthesis uses CO 2. When the two processes are in balance there is no net production of CO 2 and we call this point the compensation point. We can use neutral density (ND) filters to find the light level at which this compensation point is reached. Neutral density filters reduce transmittance of all wavelengths of light. As the ND rating increases, the amount of light transmitted into the bottle decreases and so the indicator solution containing the algal balls goes more yellow as photosynthesis slows down and respiration takes over. 1. Wrap one of the three different ND filters around three different bijou bottles 2. Check there are no gaps and then fix the filters into place with sticky tape 3. Leave a fourth bottle with no filter, and a fifth bottle covered in black paper 4. Place the same number of balls into each of the small bottles 5. Fill each bottle full with hydrogen carbonate indicator solution and replace the lid 6. Place the bottles equal distances away from a switched off light source, making sure the sticky tape faces away from the light 7. Once they are all in place, switch on the light and leave for 30 mins 8. When the time is up switch off the lamp. Use a pipette the remove the indicator solution from one of the bottles and pipette this solution into a cuvette. 9. Place the cuvette into the colorimeter set at an absorbance of 550nm and record the reading. 10. Repeat with the solutions from the other bottles using clean cuvettes each time 11. Plot a graph of absorbance at 550nm against % light transmitted into the bottle 12. Find the value of light intensity at the compensation point (when absorbance is 0) Filter on bottle % light transmitted into the bottle Absorbance at 550nm 0.00 ND (no filter) ND ND ND ND (black paper) 0

7 Introduction Investigation 4: Light Colour / Wavelength You will either have made or been given some algal balls. You are going to use them to investigate the question Does light colour (wavelength) affect the rate of photosynthesis? 1. Wrap different colour (red, blue, green) acetate round each of three bottles. Take care not to leave gaps where white light could get in. 2. Leave a fourth bottle with no acetate, and a fifth bottle covered in black paper 3. Place the same number of algal balls into each of the small bottles 4. Fill each bottle full with hydrogen carbonate indicator solution and replace the lid 5. Place the bottles equal distances away from a switched off light source and with any sticky tape facing away from the lamp 6. Switch on the light and leave for 30 mins 7. When the time is up, remove the acetates, and record the colour and /or ph in each tube Bottle covering Colour of light being transmitted into the bottle Colour of light being blocked by the acetate so not getting into the bottle colour / ph value after 30 mins Filters act by absorbing some colours of light and letting other colours through. So for instance, a red filter looks red because it is absorbing all the other colours except for red, and it is allowing red to pass through it (it transmits red light). 1. What coloured light is getting into each of your bottles? 2. What process in plants uses carbon dioxide? 3. In which of your bottles will this process be taking place? Explain. 4. What process in living things (including plants) produces carbon dioxide? 5. In which of your bottles will this process be taking place? After you have collected your results, compare them to other groups near you. Can you answer the question you were investigating and suggest under which colour light do algae have the fastest rate of photosynthesis?

8 Investigation 5: Number of algal balls/concentration of algae Introduction You will either have made or been given some algal balls. You are going to use them to answer the question Does the number of algae/algal balls increase the rate of photosynthesis? 1. Place a different number of algal balls in each of your bijou tubes (make sure there is a regular interval between the different numbers) or 2. Place the same number of algal balls in each of your bijou tubes, making sure that each bottle contains algal balls of a different algal concentration to the other bottles 3. Fill each bottle full with hydrogen carbonate indicator solution & replace lid 4. Make sure each tube has equal and safe illumination by a lamp 5. Switch on the lamps and set your timer for the time you have chosen 6. When the time is up, record the colour and /or ph in each tube Number of algal balls Or Concentration of algae in the algal balls 0 (control) Colour / ph of indicator Colour / ph of indicator 1. What process in plants uses carbon dioxide? 2. In which of your bottles will this process be taking place? - explain 3. What process in living things (including plants) produces carbon dioxide? 4. In which of your bottles will this process be taking place? 5. What are your overall predictions? Will the colour change in all of your bottles? Will it be faster in some bottles than others? Explain your predictions. After you have collected your results, compare them to other groups near you and say whether they fit your predictions. Try to explain any anomalies (odd results). Can you answer the question that you were investigating?