The second major event in the evolution of metabolism was most likely which of the following?

• A. The emergence of aerobic respiration
• B. The evolution of multicellularity
• C. The development of anaerobic photosynthesis
• D. The origin of glycolysis

Answer: (C)

Verified step by step guidance

1. Understand the context of the question: The evolution of metabolism refers to the sequence of biochemical processes that organisms developed over time to harness energy from their environment. This question asks about the second major event in this evolutionary timeline.
2. Recall the first major event in the evolution of metabolism: The origin of glycolysis, which is a universal pathway for breaking down glucose to produce energy, is widely considered the first major event. Glycolysis is anaerobic, meaning it does not require oxygen.
3. Analyze the options provided: The emergence of aerobic respiration requires oxygen and likely occurred later in evolutionary history. The evolution of multicellularity is unrelated to the biochemical processes of metabolism. Anaerobic photosynthesis, which uses light energy to produce organic molecules without oxygen, is a plausible second event. Glycolysis, as mentioned earlier, is the first event, not the second.
4. Consider the environmental conditions of early Earth: Early Earth had little to no oxygen in its atmosphere, so metabolic processes that did not rely on oxygen, such as anaerobic photosynthesis, would have been advantageous and likely developed before aerobic respiration.
5. Conclude that the second major event in the evolution of metabolism was likely the development of anaerobic photosynthesis, as it represents a significant advancement in energy acquisition and aligns with the conditions of early Earth.