Origin of Life

The origin of life on earth is one of the mysteries to mankind. According to a common man, life is gifted by god whereas scientists believe that life has originated from non-living matter by natural means. This mystery of whether life originated from non-living matter was solved by scientists Pirie. It has been proved that the first non-cellular forms originated 3 billion years back from RNA, Protein, Polysaccharides, etc. The first cellular form of life was single cells that did not possibly originate till about 2000 million years ago. All life forms were present in the water only.

Also Read: RNA

What is the Evolution of Life?

Life is an inherent property of an organism by which it maintains and reproduces itself. There are different life forms (unicellular, multicellular, prokaryotes, eukaryotes, etc.) on this earth and these life forms are supposed to have evolved from simple organic molecules. This process in which an organism evolves from simple organic molecules in a gradual period of time is called evolution. The term evolution was first coined by Herbert Spencer. This is supposed to be how the evolution of life took place on this earth 500 million years after the formation of the earth, i.e., almost four billion years ago. To understand the origin of life on earth, it is very important to understand the origin of the universe.

Origin of Universe

The most accepted theory of the origin of life on earth is the Big Bang theory.

Big Bang Theory

 

This theory was proposed by Abbe Lemaitre in 1931. According to this theory, 15 billion years ago cosmic matter was in condensed form.
This condensed mass consisted of neutrons, protons, and electron-like particles.  Suddenly, this condensed mass exploded, and its fragments (cosmic materials or nebulae) got scattered into space at an enormous velocity making a “big bang” sound and thus the theory is known as the big bang theory. From the exploded fragments (cosmic materials or nebulae) the solar system was formed.

Formation of the Solar System and Earth

The nebular hypothesis explains the origin of the solar system. It was first proposed by Kant in 1755.  After the explosion, solar nebulae gradually cooled and contracted to form a cold cloudy mass of cosmic dust and gases.  As the universe expanded, the temperature decreased, and various galaxies were formed. For example-Milky Way galaxy. This galaxy consists of a solar system, in which the earth is present. Earth is one of the planets of the solar system and originated about 4.6 billion years ago.  When the earth was formed there was a rotating cloud of hot gases and cosmic dust called a Nebula.  There was no atmosphere on earth. The UV rays split water into Hydrogen and Oxygen and the lighter H2 escaped.  Water vapor, methane, carbon dioxide, and ammonia released from molten mass covered the surface. Oxygen reacts with ammonia and methane to form water, CO₂, and others.  Water vapor formed the rain and water fell down and filled all the depressions and formed oceans. First life emerged 500 million years after the formation of the earth, i.e., almost four billion years ago.

Theories of the Origin of Life

Once, the earth is formed then life starts appearing. There are several theories that give their own observations regarding the origin of life on earth. A few of them are discussed as follows:

1. Cosmozoic Theory (Panspermia): It was given by Richter in 1865. According to this theory, spores or seeds were the unit of life that got transferred to different planets and developed into life. These spores were known as panspermia.
2. Theory of spontaneous generation: This theory was given by Von Helmont. According to this theory, life originated abiogenetically (suddenly and spontaneously) from decaying and rotting matter like straw, mud, etc. However, the theory was strongly disapproved by Francisco Redi, Lazzaro Spallanzani, and Louis Pasteur who proved experimentally that life can originate only from pre-existing life forms. This is known as the theory of biogenesis.

FAQs on Origin of Life

Question 1: What is Biopoiesis?

Answer: 

The process of development of living organisms from non-living matter is known as biopoiesis.

Question 2: What is the Theory of Biogenesis?

Answer: 

The theory of biogenesis states that life has evolved from pre-existing life forms.

Question 3: What is the Theory of Abiogenesis?

Answer: 

Theory of abiogenesis states that life originated abiogenetically (suddenly and spontaneously) from any kind of non-living matter like mud, dust, etc.

Question 4: What is the Nebular Hypothesis? 

Answer: 

According to this theory, the solar system arrived at its current form after collapsing from a molecular gas cloud some 4.568 billion years ago.