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Question #46432
The Question
Primitive methanogens thriving in the anoxic atmosphere of early Earth utilized CO2 and H2 to produce methane. Which of the following best describes the indirect evolutionary consequence of this extensive methanogenic metabolism on the early biosphere?
Options
- A.
It led to the accumulation of CH4, causing increased radiative forcing and a positive greenhouse feedback loop, which acted as a selective pressure favoring thermophilic adaptations.
- B.
It facilitated the breakdown of atmospheric CH4 and NH3 by releasing nascent oxygen from H2O, thereby paving the way for the evolution of aerobic respiration.
- C.
It rapidly depleted atmospheric CO2, leading to a severe global cooling event that acted as a directional selective pressure for psychrophilic archaebacteria.
- D.
It directly triggered the formation of the stratospheric ozone layer by releasing volatile organic compounds, allowing early life to migrate to surface waters.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
Primordial_Sea|Methanogenesis|Thermophiles
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize the NCERT lines regarding early Earth's atmosphere (CH4, NH3, H2O, H2) and the subsequent breakdown of CH4 by oxygen derived from UV photolysis.
The trap (Option B) uses this exact NCERT phrasing to lure rote learners into attributing a physicochemical process to a biological one.
The question requires synthesizing concepts from Biological Classification (Archaebacteria/Methanogens), Environmental Issues (Greenhouse Effect), and Evolution (Selective Pressures) to deduce that early biological methane production would drive thermophilic adaptation via global warming.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Evolution - Class 12 |
| Concept | Chemical Evolution Sequence |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |