Question at position 17 Which is thought to be the original energy source for the metabolism of the first living cells?PhotosynthesisGeothermal heatSolar energyLightningFireClear my selection

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BlackTom AI · Accepted Answer

To tackle this question, let’s evaluate each proposed energy source in the context of how the first living cells likely obtained energy.
Option 1: Photosynthesis. While photosynthesis is a major energy-harvesting process in many modern plants and some microbes, it is generally considered to have evolved after the earliest life forms. The very first metabolism is thought to have relied on chemical energy from the environment rather than light-driven processes. This makes photosynthesis unlikely as the original energy source for the earliest cells.
Option 2: Geothermal heat. This choice aligns with models of early Earth biology that emphasize chemotrophic metabolism powered by chemical energy derived from geochemical energy sources, such as redox reactions at hydrothermal vents or geothermal gradients. Such settings provide steady chemical energy without requiring light, supporting the idea of heat-driven, inorganic-energy–based metabolism in the origin of life.
Option 3: Solar energy. Solar energy is abundant on Earth today, but the earliest life likely could not directly harness sunlight before photosynthesis evolved, and even after photosynthesis developed, the very first metabolic systems probably did not rely on solar energy as their primary source. Therefore, solar energy is not the best fit for the original energy source of the first cells.
Option 4: Lightning. Lightning produces energy and can drive some chemical reactions, but it is episodic and not a reliable, sustained energy source for the continuous metabolism envisioned for early cells. This makes it an unlikely primary energy source for the origin of metabolism.
Option 5: Fire. Fire is a high-temperature chemical process that would require oxygen and is destructive rather than a controlled energy-harvesting mechanism suitable for the emergence of metabolism. It does not provide a plausible sustained energy source for the earliest life forms.
In sum, when considering mechanisms available to early Earth and the need for a continuous, reliable energy source to support primitive metabolism, geothermal heat (chemical energy from geochemical environments) stands out as the most plausible origin of metabolic energy for the first living cells, while the other options either postdate early metabolism or lack the continuity and suitability required for primordial life processes.

Question at position 17 Which is thought to be the original energy source for the metabolism of the first living cells?PhotosynthesisGeothermal heatSolar energyLightningFireClear my selection

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