Origin of Life for CBSE Class 12 Biology
- Last Updated Dec 21st 2022
The origin of life is viewed as one of a unique event in the history of the entire existence of the universe.
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Overview
Learn Origin of Life Biology | CBSE Class 12
The universe is huge. Generally the earth itself is practically just a bit. The universe is old – right around 20 billion years of age. Huge clusters of galaxies comprise the universe. . Universes contain stars and clouds of gas and dust.The air was absent on early earth.
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Basic Requirement
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Class 12 Student
Skills Covered
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The Biogenesis Theory
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The Theory of Oparin Haldane
Expert Review
Life and the universe are very closely related and both are integral parts of each other. We know that in our universe, matter has achieved "life is the most unique, complex organization of molecules, manifesting itself through chemical reactions leading to growth, development, responsiveness, adaptation, and reproduction". The origin of life is a unique event in the history of the
(i) Ancient theories of the origin of life: A variety of theories have been put forward to explain the phenomenon of the origin of life. Several were based only on speculation, while others had a scientific basis. The theories are as follows:
(a) Theory of special creation :
The whole universe was created in six days by God, according to a Spanish priest Father Suarez (1548 - 1617 B.C. ). God created the Earth and heaven on the first day, the sky on the second, dry land on the third, the sun on the fourth, fishes on the fifth, and animals and humans on the sixth day. It was based on some supernatural power.
(b) Theory of spontaneous generation or Abiogenesis :
According to this theory, life evolved spontaneously from non-living matter from time to time. The theory was supported by Plato, Aristotle, Anaximander, John Ray, Needham, Von Helmont, etc., up until the end of the seventeenth century. He argued that life originated from preexisting life and rejected the theory of evolution.
Life originates from non-living organisms through abiogenesis.
(c) Biogenesis:
The Biogenesis concept of Huxley was experimentally supported by scientists such as Redi (1668), Spallanzani (1767), and Louis Pasteur (1866–1862).
Francesco Redi (1668) demonstrated that maggots cannot be created from meat. Flies lay eggs on meat because of the smell of meat. The eggs hatch into flies.
Even primitive, unicellular organisms cannot arise from non-living matter, as Spallanzani (1767) demonstrated.
In 1860, Louis Pasteur (1860-62) obtained air samples from flasks of broth (yeast and sugar solution) that were sealed with a partial vacuum. Samples were obtained by opening the flasks. The flask was resealed after air was drawn in. The flasks were incubated. When flasks were opened on the streets, they became turbid, while those exposed to dust-free air rarely contained bacteria.
Similarly, Louis Pasteur employed swan-necked flasks whose long, curving necks allowed air to circulate between the outside and inside of the flask, but dust and bacteria were trapped along the neck wall. When the flask was tilted, bacteria got washed into the broth, resulting in cloudy broth because of bacterial growth.
(d) Cosmozoic or Extraterrestrial or Interplanetary or Panspermiatic Theory:
Richter (1865), Preyer (1880), Arrhenius (1908), Hoyle (1950) and Bondi (1952) all believed in eternal life. Arrhenius claimed that life was transferred to different planets from "cosmozoa" (life in outer space) in small units known as "spores". Spores were covered with a thick protective layer. Spore coats dissolve under favorable conditions and temperatures, giving rise to living organisms. Life cannot have originated in space or in spores impervious to ultraviolet and gamma radiation, according to this theory.
(e) Theory of Catastropism or Theory of sudden creation from inorganic material :
Catastrophism was a belief of Cuvier (1769-1832). He argues that after the catastrophe, new life arises on earth, which he calls the mechanistic theory.
(ii) Modern Theory / Oparin Haldane Theory / Chemical Theory / Naturalistic Theory / Materialistic Theory :
Haldane, a British scientist, suggested that carbon dioxide, ammonia, and water vapour predominated in the early atmosphere. When ultraviolet rays reacted to them, organic molecules were formed. Gradually, the quantity of these oceans which later gave rise to amino acids, proteins, carbohydrates, nucleic acids, etc.
Oparin's Modern Theory :
Oparain (1924) argued that life could have evolved from non-living organic molecules. He believed in the biochemical origin of life. Haldane (1929) held similar views. Oparin presented his ideas in "The origin of life" in 1936, which greatly expanded them.
The Earth originated about 4,500 million years ago, according to this theory. At that time, its atmosphere was reduced. The primitive atmosphere contained nitrogen, hydrogen, ammonia, methane, carbon monoxide, and water. Electric discharges caused by lightning and ultraviolet rays provided energy. During the formation of the earth's crust, it was folded heavily. For centuries, torrential rains dumped their contents deep into the earth.
In deep oceans, atmospheric compounds, inorganic salts, and minerals were found, and these molecules gave rise to a variety of compounds and then to the self-replicating molecules. These molecules were eventually enclosed in membranes made of lipids and proteins with water and chemical compounds, giving rise to cells. It is possible that random combinations led to the emergence of chlorophyll-containing organisms capable of producing their own food (autotrophs) through a process called photosynthesis. Due to the fact that they synthesized starch from carbon dioxide and water in the presence of sunlight, these organisms had a better chance of surviving.
Oxygen is produced during photosynthesis. Other organisms use the oxygen to breathe. Oxygen also forms an ozone layer when it is exposed to ultraviolet rays. Around 25 kilometers of this layer is formed. From the earth's surface. In the past, organisms that were thrown out of the ocean could survive on land if they reached the surface of the ocean because of the formation of the ozone layer. The Oparins's and Haldane's theories of life's origin are the most accepted theories of origin as they are supported by Miller's experiment, David Buhal's experiment, Melvin Kelvin's experiment, etc.
During the origin of life, there was no oxygen in the primordial atmospheres.
There are many other theories about the origin of life. Join the course today.
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