Origin of life
Topic: Origin and Evolution of the Earth and the Solar System · NCERT: Class 11, Ch 2 "The Origin and Evolution of the Earth"
Meaning
The origin of life is the last phase in the evolution of the Earth. The early Earth and its atmosphere were not suited to life. Life arose through chemical reactions. These first formed complex organic molecules (carbon-based building blocks), and then the molecules became arranged so they could copy themselves. In this way, lifeless matter turned into living matter. Life began about 3,800 million years ago and stayed in the oceans for a long time. It moved onto land only about 500–450 million years ago, after oxygen and the ozone layer had built up.
Example
The Miller-Urey experiment (1953) sent electric sparks through a copy of the early atmosphere and produced amino acids. This supports the Oparin-Haldane "primordial soup" idea. Hydrothermal vents (hot springs on the sea floor) are another possible setting for the start of life. These vents are found along ocean ridges such as the Mid-Atlantic Ridge in the Atlantic Ocean.