7 theories of origin of life on earth
Answers
Answer:
1 Panspermia.
2 Simple Beginnings. ...
3 RNA World. ...
4 Chilly Start. ...
5 Deep-Sea Vents. ...
6 Community Clay. ...
7 Electric Spark. ...
Answer:
Panspermia
In olden days, people believed that the universe and life on it was an act and result of God’s creation. There was, however, no evidence to support these claims.The early scientists and Greeks believed that life on earth never began on earth itself. They believed that it came from somewhere else in outer space and they named this phenomenon ‘panspermia’.
Simple Beginnings
Instead of developing from complex molecules such as RNA, life might have begun with smaller molecules interacting with each other in cycles of reactions. These might have been contained in simple capsules akin to cell membranes, and over time more complex molecules that performed these reactions better than the smaller ones could have evolved, scenarios dubbed "metabolism-first" models, as opposed to the "gene-first" model of the "RNA world" hypothesis.
RNA World
Nowadays DNA needs proteins in order to form, and proteins require DNA to form, so how could these have formed without each other? The answer may be RNA, which can store information like DNA, serve as an enzyme like proteins, and help create both DNA and proteins
Later DNA and proteins succeeded this "RNA world," because they are more efficient. RNA still exists and performs several functions in organisms, including acting as an on-off switch for some genes. The question still remains how RNA got here in the first place. And while some scientists think the molecule could have spontaneously arisen on Earth, others say that was very unlikely to have happened.
Chilly Start
Ice might have covered the oceans 3 billion years ago, as the sun was about a third less luminous than it is now. This layer of ice, possibly hundreds of feet thick, might have protected fragile organic compounds in the water below from ultraviolet light and destruction from cosmic impacts. The cold might have also helped these molecules to survive longer, allowing key reactions to happen
Deep-Sea Vents
The deep-sea vent theory suggests that life may have begun at submarine hydrothermal vents, spewing key hydrogen-rich molecules. Their rocky nooks could then have concentrated these molecules together and provided mineral catalysts for critical reaction
Even now, these vents, rich in chemical and thermal energy, sustain vibrant ecosystems.
Community Clay
The first molecules of life might have met on clay, according to an idea elaborated by organic chemist Alexander Graham Cairns-Smith at the University of Glasgow in Scotland
These surfaces might not only have concentrated these organic compounds together, but also helped organize them into patterns much like our genes do now.
Electric Spark
Electric sparks can generate amino acids and sugars from an atmosphere loaded with water, methane, ammonia and hydrogen, as was shown in the famous Miller-Urey experiment reported in 1953, suggesting that lightning might have helped create the key building blocks of life on Earth in its early days. Over millions of years, larger and more complex molecules could form
Although research since then has revealed the early atmosphere of Earth was actually hydrogen-poor, scientists have suggested that volcanic clouds in the early atmosphere might have held methane, ammonia and hydrogen and been filled with lightning as well.
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