Biggest questions in front of scientists are How did life origin on Earth? How did we all come into existence? Why are there so many species on Earth? The answer to these questions is not that obvious. These questions have puzzled scientists and researchers from many centuries. Yet we don’t have concrete answers to all these questions.
We will try to explore the possibilities in the light of our scientific knowledge….
Before we understand how did life origin, we need to know …….
What are we made up of?
From our knowledge of Biology, we can say that all the living beings are made up of CELLS. Cell is the structural and functional unit of all living organisms. So, we can say that we are like what we are because of CELLS. Cells are made up of biomolecules like proteins, carbohydrates, nucleic acid, etc. These biomolecules are in turn made up of carbon, hydrogen and oxygen. From all this we can deduct that we are made up of Carbon, Hydrogen and Oxygen. Now an obvious question should arise that…….
How old is life on the Earth?
Researchers have found the oldest rock with the evidence of fossils on it which is 3.5 billion years old. There are few more rocks which have chemical traces on it. This chemical is the signature of carbon isotope which is produced by living organisms. This rock is 3.8 billion years old. So, we can say that life on Earth is somewhere between 3.5 to 3.8 billion years old. The oldest known living being on Earth is dinosaur which existed 250 million years ago and atmosphere at the beginning of Earth’s origin was way different than it is today.
Early Earth’s atmosphere
Early Earth just few centuries after its creation comprised of liquid water, hot gases and carbon- based chemicals. The gases included hydrogen in abundance, methane and ammonia mainly. There was one more gaspresent in abundant and that was carbon dioxide. All this knowledge is enough to say that life on Earth originated accidentally. The accidental origin of life
This theory tells that life originated accidentally. Earth after its origin was too hot. Eventually is cooled down and rained. The rain on the early Earth had two different effects. Firstly, the rain reacted with the chemicals, present then in abundance in the atmosphere, and formed complex compounds like sugar, amino acid, etc. Secondly, the rain water after reaction formed some microscopic structure that didn’t dissolve in water like oil. These microscopic structures formed coacervates (which are organic rich droplets formed by liquid-liquid phase separation). Researchers attempted to recreate them in lab. These coacervates when observed under microscope gave shocking results. Their behavior changed like a living cell. They grew and changed shape as well. One more shocking thing noticed was that they divided into 2 parts like living cells do when reproducing. So, it might be possible that the first living cell might have originated accidentally and eventually evolved. One more evidence to support this theory came in the year 1828
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Preparation of life building chemicals in lab
In 1799, urea was discovered in urine. It was believed that urea cannot be prepared in lab, it can only be produced by a living body. But in the year 1828, synthesized urea from ammonium cyanate. This discovery brought a revolution in our thinking of the origin of life. It brought an end to Vitalism (the belief that living organisms are different from non-living things). This also proved that urea has no connection with living being, as it was thought. More evidence in support of the theory came in 1952 …….
Miller-Urey experiment
In 1952, Stanley Miller and Harold Urey conducted an experiment. A series of glass was connected. Four chemicals were circulated i.e. boiling water, methane, hydrogen and ammonia. These gases were selected because these were present in the early Earth’s atmosphere. These were subjected to repeated electric shocks (trying to imitate thunderstorm). The observations were shocking. After 1st day the solution turned pink and after a week the solution became deep red and turbid. The experiment was repeated by changing the conditions many times (all same as that existed on early Earth). A mixture of chemicals was obtained. These included glycine and alanine in large quantity, which are amino acids. Amino acids are the building block of life. This experiment synthesized 2 important components of life from scratch by using the things that might have been present in the early Earth. This made clear that life existed from the non-living things …
Life originated from non-living stuff
It is well known fact that 99% of the mass of Universe and that of life is composed of just 6 elements. Those are hydrogen (87%), helium (12%), carbon (0.03%), nitrogen (0.008%), oxygen (0.06%) and neon (0.02%). Shocking right?
Some more shocking results are: -
✓ In 17th century, William Harvey showed that every animal come from an egg
✓ In 17th century, Francesco Redi told that maggots in meat come from flies’ egg
✓ In 1850, Louis Pasteur proved that most minute creature come from germs floating downwards in air.
A botanist, B.S. Haldane gave a hypothesis that all living organisms are formed purely by chemical means. The organic chemicals which are the building blocks of living cells could be build up in water. Though, he didn’t give any experimental evidence but this hypothesis makes sense if we correlate it with the results of Miller-Urey experiment. There are several methods by which organic molecules can be produced non biologically. So, it is possible that these organic molecules might have formed from hydrogen in the early atmosphere.
Moreover, most of the essential building blocks of protein, carbohydrate and nucleic acid can be prepared in the conditions that prevailed on early Earth. If life is formed accidentally then why so many different species? the answer lies here …
Theory of Evolution
This theory was proposed by Charles Darwin. It tells that all life on Earth is correlated. All living organisms have arisen from single ancestor. The vast diversity of life is due to modification of population by natural selection. Some traits favored in environments over the
other traits. Natural selection is the process where the organisms with favorable traits are more likely to reproduce. It is of 2 types :-
1. Microevolution
In this type there are minor changes like color change, size change, etc. for example the sparrows in northern latitudes are large bodied than sparrows in the south.
2. Macroevolution
This kind of evolution needs more time. This type of changes includes complete species change into a new one. For example, apes evolved to humans.
Life has originated on Earth 3.5 billion years ago. The biomolecules which are the building blocks of living beings can be prepared in lab in the conditions that prevailed on early Earth. A 2016 study showed that all living things have their origin from bacterium. Hence proving the point of Theory of Evolution. So, it is proved from all this that life has originated from nonliving things accidentally and eventually evolved according to the suitable environmental conditions. With due course of time scientist will prove it scientifically.
Very comprehensively yet concisely articulated... Keep it up, budding scientist...
ReplyDeleteThankyou so much ❤️❤️❤️ keep supporting 🤗🤗
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