Before You Begin
Question #46433
The Question
According to the standard geological time scale, the first cellular forms of life appeared approximately 2000 million years ago (mya). The energy for the preceding chemical evolution was primarily provided by UV radiation and lightning. If a hypothetical decrease in early solar UV intensity had prolonged this chemical evolution phase, delaying the appearance of the first cellular life to 1000 mya, which of the following evolutionary events would be most directly subjected to temporal compression (i.e., forced to occur in a much shorter geological window)?
Options
- A.
The formation of the first non-cellular forms of life (giant macromolecules) from simple organic compounds.
- B.
The cooling of the Earth, condensation of water vapor, and the dissolution of atmospheric CO2 into primitive oceans.
- C.
The biological release of free oxygen into the atmosphere and the subsequent endosymbiotic origin of eukaryotic cells.
- D.
The formation of protobionts like coacervates and microspheres exhibiting differential permeability.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Comparative_Analysis
Sharpen your ability to evaluate multiple scenarios and distinguish between competing potential answers.
Concepts Behind This Question
Urey-Miller_Experiment|Cenozoic_Eras|Hominid_Evolution
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize the evolutionary timeline (4.5 BYA, 3 BYA, 2 BYA) without understanding the causal dependency between the stages.
The pivot here is recognizing that biological oxygenation and eukaryotic endosymbiosis are strictly 'post-cellular' events.
The trap relies on the student failing to distinguish between the prolonged pre-cellular phase (Options A, B, D) and the compressed post-cellular phase (Option C).
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 |