| Explore | We already knew that plants grow by photosynthesis, and need light and carbon dioxide and water to produce glucose and oxygen. We have not yet learned anything else in class yet this year in Honors Biology. |
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| Research Question | Does the lack of light energy affect whether photosynthesis occurs? |
| Predictions | If light energy is necessary for photosynthesis, then algal balls in the dark will not perform photosynthesis and the pH will stay low which means the color of the phenol red will not change. |
| Experimental Design | Materials: Chlorella algae (prepared suspension) Prepared sodium alginate Prepared 0.2% sodium bicarbonate 6 small beakers pipet (tip cut) light source box Procedures: Prepare 120 algal balls as per instructions Label 6 small beakers: Light 1, Light 2, Light 3, Dark 1, Dark 2, Dark 3 Add to each beaker: -5 mL prepared 0.2% sodium bicarbonate solution -5 mL prepared phenol red indicator -20 algal balls Using pH test strips, test and record initial pH Record initial color Place Light 1, 2 and 3 beakers under light source Place Dark 1, 2 and 3 beakers under box Record color and pH every 5 minutes for 30 minutes Independent Variable: light Dependent Variable: pH (as indicated by pH test paper and phenol red indicator) Record data in table |
| Conclusion | We weren't able to make a claim because the evidence did not support a claim about the effect of light on photosynthesis in algal balls in this experiment. We had several possible sources of error: algal balls contained very low density of algae, algal balls were small, quantity of algal balls per volume may not have been adequate to result in enough photosynthetic activity to see results, use of sodium bicarbonate may have acted as a buffer- follow up discussion of using breath as a source of CO2, |
