What adaptation allows cacti to efficiently conserve water in arid environments, making them crucial for the survival of animals in these ecosystems?

Why is it difficult for C3 plants to carry out photosynthesis in very hot, dry environments such as deserts?

a. The light is too intense and destroys the pigment molecules.

b. The closing of stomata keeps CO₂ from entering and O₂ from leaving the plant.

c. They must rely on photorespiration to make ATP.

d. CO₂ builds up in the leaves, blocking carbon fixation.

How is photosynthesis similar in C4 plants and CAM plants?

a. In both cases, the light reactions and the Calvin cycle are separated in both time and location.

b. Both types of plants make sugar without the Calvin cycle.

c. In both cases, rubisco is not used to fix carbon initially.

d. Both types of plants make most of their sugar in the dark.

To synthesize one glucose molecule, the Calvin cycle uses _________ molecules of CO₂, _________ molecules of ATP, and _________ molecules of NADPH.