Answer: Adaptation to arid conditions -- temporally separating CO 2 fixation (night) from Calvin cycle (day) to minimize water loss.
- A An adaptation enabling survival specifically in persistently cold, frost-prone alpine and arctic mountain climates in routine practice
- B Adaptation to arid conditions -- temporally separating CO<sub>2</sub> fixation (night) from Calvin cycle (day) to minimize water loss
- C An adaptation for capturing limited light filtering down through deeply shaded forest understory regions overall in most cases
- D An adaptation allowing root respiration to continue normally within waterlogged, oxygen-poor soil environments under typical conditions
Correct answer: B. Adaptation to arid conditions -- temporally separating CO<sub>2</sub> fixation (night) from Calvin cycle (day) to minimize water loss
Explanation: CAM: evolved in desert plants (cacti, agaves, succulents) for maximal water use efficiency. Night CO<sub>2</sub> fixation (PEP carboxylase) stores CO<sub>2</sub> as malate; day decarboxylation feeds Calvin cycle with stomata closed.
Simplified photosynthesis diagram: light energy, CO2, and H2O enter the leaf and are converted in the chloroplast into glucose and O2.
Concept context
Light reactions, the Calvin cycle, C 3 /C 4 /CAM pathways, photorespiration, and factors affecting the rate of photosynthesis. One of the highest-yield NEET chapters.