To determine the correct chronological order of the events listed, we need to understand the sequence of biological and atmospheric changes in Earth's history:
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Single-celled organisms increase atmospheric methane concentrations - This event would occur very early in Earth’s history as primitive life forms were established.
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Photosynthesizing bacteria release oxygen into the sea - This happened with the emergence of cyanobacteria, which began the process of photosynthesis and released oxygen, leading to the oxygen being dissolved in the oceans.
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Oxygen concentrations increase in the atmosphere - Following the increase in dissolved oxygen in the seas, eventually oxygen levels also began to rise in the atmosphere, notably during the Great Oxidation Event.
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Many new animal species evolve - The rise in oxygen levels in the atmosphere paved the way for the evolution of multicellular organisms and eventually many new animal species.
Given this understanding, the correct chronological order is:
Single-celled organisms increase atmospheric methane concentrations. Photosynthesizing bacteria release oxygen into the sea. Oxygen concentrations increase in the atmosphere. Many new animal species evolve.
This sequence matches the third select option:
Single-celled organisms increase atmospheric methane concentrations. Photosynthesizing bacteria release oxygen into the sea. Oxygen concentrations increase in the atmosphere. Many new animal species evolve.
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