Photosynthesis is a process carried out by the cells of autotrophic organisms in order to synthesize their own food in form of sugars (glucose). As rightly stated in this question, Carbon dioxide (CO2) is a major ingredient for this process to occur. Inorganic CO2 enters an organism like plankton and is used to make organic molecules.
The organic molecules produced via the photosynthetic process are in form of sugar (glucose) i.e. C6H12O6 whose principal elemental component is CARBON. In other words, the organic molecules contain carbon in their structure, got from the CO2 source.
Student 1’s methods would be more accurate, because the student would control more factors. Only one variable at a time (either temperature or acidity) would be tested on each group of worms. On the other hand, Student 2 is testing both factors on all the worms, which could make the results unclear.
