Many different microscopic organisms can be found in pond ecosystems, including the three organisms shown in the diagrams below. The primary cellular structures in each of these single celled organisms are labeled in the diagram. Some of the structures are common to all three organisms and other structures are not. One of the three organisms below can obtain energy through photosynthesis. a. Based on the diagrams, identify which organism is able to perform photosynthesis. Explain your reasoning.

b. Identify the two reactants for photosynthesis.

c. At times, this photosynthetic organism can switch to being heterotrophic. Describe a condition that would favor this organism being heterotrophic. Explain your answer.

Answer using 2 to 3 complete sentences for each question.