AP BIOLOGY

Detailed explanation-1: -High water temperature, absence of oxygen and of living organisms facilitated chemical reactions between above mentioned gases to form simple organic compounds such amino acids, fatty acids, glycerols and nucleotides.

Detailed explanation-2: -Earth’s earliest climates, before 4000Ma, reflected a relatively faint young Sun and a soupy greenhouse atmosphere rich in dust and gas, such as CO2 and NH3, generated by asteroid impacts, magmatic degassing, and high radioactive heat flux.

Detailed explanation-3: -Oxygen is produced by plants by the process of photosynthesis, earlier there were no plants and vegetation, which’s why no oxygen in the early atmosphere.

Detailed explanation-4: -In a paper appearing today in Science Advances, the team reports that the Earth’s atmosphere experienced the first significant, irreversible influx of oxygen as early as 2.33 billion years ago. This period marks the start of the Great Oxygenation Event, which was followed by further increases later in Earth’s history.