Origin of Life on Earth
Looking at pictures of extinct prehistoric animals, it's hard to
believe that they once roamed our planet. In fact, the Earth
and its life forms were originally quite different. Understanding
the changes in life forms on Earth over millions of years
requires understanding how life originated. The origin of life
forms, or biodiversity, is interlinked with the evolution of the
Earth, which is closely associated with the evolution of the
universe.
The Big Bang Theory
The universe is vast and comprises many galaxies. It is almost
twenty billion years old. The Big Bang theory attempts to
explain the origin of the universe. According to this theory, a
singular huge explosion caused the infinitesimally small, hot,
and dense universe to expand, which resulted in lowering
temperatures. The theory states that the universe continues to
expand even today. After the passage of time, gases such as
hydrogen and helium formed. They condensed due to
gravitation and gave rise to different galaxies in the universe.
One of these galaxies is the Milky Way, which contains our
solar system. The Earth is one of the planets in this system.
Formation of the Earth
At the time of its formation, there was no atmosphere on Earth.
Its surface was covered by water vapor, methane, carbon
dioxide, and ammonia released from the molten mass.
Gradually, the ultraviolet rays of the sun broke up the water,
which was in vapor state, into hydrogen and oxygen. Hydrogen
being a lighter gas than oxygen escaped. Thereafter, oxygen
combined with ammonia and methane, which led to the
formation of water, carbon dioxide, and other gases. The high-
energy ultraviolet rays of the sun struck the oxygen molecule
and split it into oxygen atoms, which in turn reacted with other
oxygen molecules to form ozone. Thus, the ozone layer was
formed. Some of the water vapor cooled and came down as
rain, which filled all the deep depressions on Earth and formed
oceans.
Theories of the Origin of Life
It is estimated that life appeared on Earth 500 million years
after its formation. There are different theories that try to
explain the beginning of life on Earth. Some of them are man's
premier spontaneous generation, biogenesis, and chemical
Looking at pictures of extinct prehistoric animals, it's hard to
believe that they once roamed our planet. In fact, the Earth
and its life forms were originally quite different. Understanding
the changes in life forms on Earth over millions of years
requires understanding how life originated. The origin of life
forms, or biodiversity, is interlinked with the evolution of the
Earth, which is closely associated with the evolution of the
universe.
The Big Bang Theory
The universe is vast and comprises many galaxies. It is almost
twenty billion years old. The Big Bang theory attempts to
explain the origin of the universe. According to this theory, a
singular huge explosion caused the infinitesimally small, hot,
and dense universe to expand, which resulted in lowering
temperatures. The theory states that the universe continues to
expand even today. After the passage of time, gases such as
hydrogen and helium formed. They condensed due to
gravitation and gave rise to different galaxies in the universe.
One of these galaxies is the Milky Way, which contains our
solar system. The Earth is one of the planets in this system.
Formation of the Earth
At the time of its formation, there was no atmosphere on Earth.
Its surface was covered by water vapor, methane, carbon
dioxide, and ammonia released from the molten mass.
Gradually, the ultraviolet rays of the sun broke up the water,
which was in vapor state, into hydrogen and oxygen. Hydrogen
being a lighter gas than oxygen escaped. Thereafter, oxygen
combined with ammonia and methane, which led to the
formation of water, carbon dioxide, and other gases. The high-
energy ultraviolet rays of the sun struck the oxygen molecule
and split it into oxygen atoms, which in turn reacted with other
oxygen molecules to form ozone. Thus, the ozone layer was
formed. Some of the water vapor cooled and came down as
rain, which filled all the deep depressions on Earth and formed
oceans.
Theories of the Origin of Life
It is estimated that life appeared on Earth 500 million years
after its formation. There are different theories that try to
explain the beginning of life on Earth. Some of them are man's
premier spontaneous generation, biogenesis, and chemical
