The cell evolution it represents all the physical and chemical changes that gave rise to the highly organized and complex structures that we know as "cells." However, even though a lot of conjecture has been made about it, it is still not known exactly how they were formed.
Cells are the basic basic units of all living things on earth. There are two markedly different cell types in nature: prokaryotic cells and eukaryotic cells..
Prokaryotic cells lack internal membrane systems and always form unicellular organisms, meanwhile eukaryotic cells are more complex, since they have internal membranous compartments and can form both unicellular and multicellular living beings..
Although they can be very different, all cells are characterized by being surrounded by a membrane, by having inside them molecules of genetic material that provide the information necessary to produce all the cellular components and multiply to give rise to another cell..
The main important task for evolutionary biologists is the demonstration of the evolution of two fundamental aspects for cellular life:
Both questions remain open today, as evolutionary biologists have made only a few inferences in this regard, without any success from the point of view of experimental demonstration..
The most accepted theories propose that the beginning of cellular evolution occurred with the origin of nucleic acid-type molecules capable of replicating (DNA and RNA).
These hypotheses, collectively known as the “RNA world”, the “primal broth” or the “primitive broth”, are based on the fact that ribonucleic acid (RNA) polymers with autocatalytic capacity to produce new short RNA fragments have been observed..
According to these theories, it is probable that many times on earth, throughout its history, ribonucleic acids, nucleotides, amino acids, simple sugars and some phosphate compounds have been formed.
Although surely many of these compounds were degraded without transcending much further, it is currently thought that it may have been the case that molecules with the ability to replicate entered lipid "bubbles" and could continue with their autocatalytic activity from the " food ”obtained from other molecules that were also enclosed in these bubbles.
It is suggested that, later, these bubbles could be divided in two due to surface tension forces, each “daughter” maintaining its internal autocatalytic activity. The complexity of these bubbles could have implied the ability to feed on sunlight and some carbon compounds.
These "precellular" processes must have occurred on earth over hundreds of millions of years, during which time different "protocells" probably originated and extinguished, positively selecting those capable of reproducing and feeding efficiently..
Thus, the protocells resulting from natural selection acting for hundreds of millions of years would be the ancestors or the most primitive forms of the ultra-complex and organized cells that we know today, which form all living beings..
Probably the first products of cellular origin were prokaryotic cells, prokaryotes or bacteria, as they are commonly known; since it is believed that these inhabited the earth about two billion years before all eukaryotic organisms.
During those two billion years, the first prokaryotic organisms continuously transformed the Earth's surface and atmosphere. These microorganisms specialized their metabolism to obtain energy from the compounds that were abundant on the planet at that time..
This "specialization" was possible thanks to the evolution of metabolic processes such as fermentation, photosynthesis, the fixation of atmospheric nitrogen and the use of oxygen in respiration, etc. These abilities developed by bacteria were only possible thanks to three main processes:
All these characteristics, together with the close cooperation between bacteria, was what most likely gave rise to eukaryotic cells..
At present there are still doubts about the origin of eukaryotic cells. However, the hypothesis most accepted by researchers is that of “endosymbiosis”, which arose from the discovery of deoxyribonucleic acid (DNA) molecules in the mitochondria of eukaryotic cells..
With this information, evolutionary biologists inferred that the descendants of bacteria that lived roughly three billion years ago in primitive oceans somehow fused or engulfed other microorganisms..
This seems to be "supported" by the characteristics of the mitochondria division, which reproduce directly by binary fission and at different times than the cell division of eukaryotic cells..
It is believed that the engulfed organism was the first "protomytochondrion" of eukaryotes, and that it provided the engulfing organism with a waste elimination system and a source of energy from oxygen, while the "protomytochondria" gained food and shelter..
This “endosymbiosis” mechanism is described as a sudden evolutionary mechanism, which in few cases could have occurred successfully and permanently.
The symbiosis between microorganisms to form new organisms together is, perhaps, the most important force of change on earth and, taking place for millions of years consecutively, could have created the great diversity of forms that we observe in all the eukaryotic cells.
Cellular evolution has been going on for a long time; In contrast, scientists have only a few decades focused on answering the questions related to this process and many are of the opinion that it is probable that before the end of the 21st century the experimental demonstration of cellular evolution could be reached..
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