Question

During which of the following intervals did life originate on the Earth?

• A. Mesozoic era
• B. Proterozoic eon
• C. Cambrian period
• D. Archean eon

Answer 1

The correct option is D Archean eon

• The Archean (or Archaean) eon is an interval of geologic time of about 1.4 billion years, beginning with the formation of Earth's crust and the oldest Earth rocks 3,960-3,800 million years ago (mya) and continuing until its boundary at 2,500 mya, with the Proterozoic eon.
• The origin of life has been traced to the Archean eon, with fossils of prokaryotes.
• During the Archean eon, prokaryotes spread over much of Earth's surface, often in mats comprising myriads of collaborating bacteria differentiated by the type of biochemistry each performed.
• During the Archean eon some prokaryotes developed the molecular structures for achieving photosynthesis, which permitted them initially to use sunlight for capturing hydrogen from the atmosphere and later to use it for capturing carbon from atmospheric carbon dioxide with the release of oxygen, thus helping to prepare an environment that could support eukaryotic cells and multicellular forms of life.
  

So the correct option is 'Archean eon'.