[Campbell Biology P.106] In Miller's control experiment, no sparks were discharged, and no o... | Practice Question

In Miller's control experiment, no sparks were discharged, and no organic compounds were found. Based on Figure 4.2 and the experimental description, what is the most likely explanation for this result?

  • A: The absence of a condenser prevented the formation of cooled 'rain' containing organic molecules.
  • B: Electrical discharges (sparks) were essential to provide the energy required for the abiotic synthesis of organic molecules from simple gases.
  • C: The water in the 'sea' flask was not heated sufficiently without the sparks.
  • D: The specific mixture of gases (H2, CH4, NH3, water vapor) cannot react without an external energy source like UV radiation, not just sparks.

Explanation

The 'sparks were discharged to mimic lightning' is explicitly stated in Figure 4.2 as a key component of the experiment. Lightning or sparks provided the high energy input necessary to break chemical bonds in the simple gases and allow them to recombine into more complex organic molecules. Without this energy, the reactions would not occur, and no organic compounds would form.