describe the various theories and experiments regarding the origin of life on earth
Answers
Answer:
There were lots of hypothesis regarding the origin of life on earth. This was followed by the theory of chemical evolution which suggested that atmospheric conditions of earth led to the formation of organic molecules from inorganic molecules. ... Few scientists conducted experiments regarding the same.
Explanation:
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Answer: Primitive Earth
The origin of life on Earth is a highly curious thing. In fact, many scientists have dedicated their entire lives to finding out how life came to be on Earth. There are a few key experiments that we will look at in order to gain an understanding of how scientists have best hypothesized how life started on Earth, but let's first take a trip back in time - about four billion years ago.
The atmosphere of primitive Earth did not contain oxygen and nitrogen, as it does now.
Primitive Earth was very different than the way things are now. There were probably many oceans and seas with many hot vents at the bottom of these waters and quite a bit of volcanic activity on land. The atmosphere most likely contained water, methane, ammonia, and hydrogen, unlike our current atmosphere, which is mostly nitrogen and oxygen.
Stages of Early Life on Earth
Now that we have an idea of what Earth may have looked like, let's take a look at what steps scientists have hypothesized led to early life. It is agreed by scientists that there are four main stages to how life came from non-living things.
The first step is that small organic molecules - such as amino acids that make proteins and nucleotides that make DNA - were made. While these organic molecules are found in living things, they aren't actually living things themselves, but are really just specific combinations of elements.
The second step is that these small organic molecules joined together to form larger molecules. The small molecules are called monomers since they are made of just one unit. However, when they join together, they create polymers that have many repeating units. You may be able to remember this because of the prefixes. 'Mono' means 'one' - like in the words monorail and monocle - while 'poly' means 'many' - like in polygon and polymorph. You can also think of it as putting paper clips together in a long chain. Each individual paperclip is a monomer, but the entire long chain of paperclips is a polymer.
The third step of early life on Earth is when things start to get a little tricky. The polymers that were formed from the monomers grouped together to form protobionts. Protobionts are very important to understanding early life. The name protobionts literally means 'early form of life,' but they are basically small droplets with membranes that are able to maintain a stable internal environment. They are similar to the cells with which we are familiar in that they can reproduce, metabolize, and even respond to their environments. Many experiments have shown that these pre-cell structures can spontaneously form.
The fourth step is that these simple protobionts evolved to pass on genetic information. Protobionts are capable of replicating - that is, they can make new protobionts. However, cells, which are the basic unit of life, are unique in that they can reproduce and pass on genetic information from one generation to the next, metabolize matter
and energy, and can evolve. These simple cells were created from complex molecules that were created from simple molecules, then continued to evolve into a wide variety of life forms.
The Oparin Hypothesis
Russian chemist A.I. Oparin
Now that we know the basic steps hypothesized to go from non-living chemicals to life, you may be asking yourself how this all happened. While we don't have a complete record of what actually happened, based on evidence and experimentation, scientists have agreed upon a few things.
The first widely accepted idea was proposed by a Russian chemist in the 1920s. A.I. Oparin proposed that the Earth's early atmosphere was very reactive and, along with lightning and UV radiation, was able to reduce substances. Now, when chemists talk of reducing substances, they don't mean making them smaller like when we reduce our debt. To chemists, reduction means adding electrons to molecules.
Along with this highly reactive atmosphere, Oparin thought that the early oceans contained an organically rich solution. This solution containing many essential elements and compounds is commonly referred to as a primordial soup. Based on this, we generally consider Oparin's hypothesis to be that early life on Earth formed through a series of reactions that made simple compounds gradually more complex.
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