The evolution of species throughout its history has allowed the emergence of impressive qualities of living things. In this post I would like to review that I believe are the 10 most significant changes that have occurred in the history of life on Earth since it first appeared living beings. Obviously these steps were all very gradual and hard to pin it down in "one step". The list is arranged in chronological order onset based on replicating the first people whose specific characteristics we can only speculate now:
1-Fidelity in DNA copy of the current
Bacteria make a mistake in copying the DNA approximately every 10E10 generations. The ratio between mutations and fidelity allows adjustments while limiting errors quickly accumulate large that would wipe out the species. The main architect of this evolutionary marvel called DNA polymerase alone is able to copy accurately several thousand DNA bases before making a mistake. The more advanced versions that appeared later in the evolution of eukaryotes also have review mechanisms to minimize mistakes. Your need for life is such that there are creatures that lack this mechanism. Only a few viruses like HIV which in turn use the cellular machinery perfect.
2-The scourge
De wait until the food arrives, go for it. This one change led to major changes in the flagellum. Although previously developed bacteria tiny hairs (cilia) that allowed some movement it is true that you were totally subject to the forces that govern Brownian motion: Imagine that you are in a pool full of marbles that are propelled at high speed in all directions . The scourge also represented an improvement in the ability to colonize new and distant environments or to escape adverse circunstanrcias. You can see a video on the evolution of the flagellum is postulated here that appeared from an organelle for the subject.
3-The photoreceptor
And there was light. The ability to recognize the light initially supposed access to food (the synthesis of many organic compounds is catalyzed by light) and a guide for the movement (defined above and below). However, this small step would sow the seeds for two mechanisms of great relevance future: photosynthesis and vision. The photoreceptors are based on pigments capable of excited with the light and transmit the excited state to a protein.
4- Photosynthesis
Who needs food when you produce it? This is perhaps the most impressive evolutionary leap: the ability to produce organic compounds from inorganic, much more abundant. These reactions require high-energy that living things get the heat, degradation of other organic / inorganic or light. Photosynthesis could not be possible without the photoreceptors also probably co-evolved with the improvement of the flagellum. None of these "house of cards" would have endured without the copying-fidelity DNA.
5-Krebs cycle and oxidative respiration
Photosynthesis brought a new era of problems or opportunities as you look. The main waste of photosynthesis is oxygen. A molecule that now seems innocuous but when it appeared it was like living in a sea of \u200b\u200barsenic. Oxygen has the capacity to oxidize DNA and proteins and interfered in many of the reactions necessary for the bacteria at the time. The emergence of atmospheric oxygen was probably a quick process that just one stroke with most species. Some species (including oxygen production) developed mechanisms to inactivate oxygen, these mechanisms are the use of electrons and protons react with oxygen to produce water. Interestingly electrons can be obtained as waste products of metabolism of organic compounds. The sophistication of the metabolism of sugars called the Krebs cycle with a complex electron transport system possible to maximize the power of organic compounds.
6-The eukaryotic cell
The complexity of the emergence of life is the only fact comparable to the emergence of the eukaryotic cell. It has been speculated that eukaryotes from the bacterial symbiosis of various types, hypothesis is more powerful genetic analysis. In any case the appearance of cells with defined nucleus and organelles is a big black box. One of the most interesting evolutionary processes that remain to be deciphered. The breakthrough of the eukaryotic cell can be described by something as simple as compartmentalization. Everything in his corner. Many of the cellular chemical reactions require a very specific environment incompatible with other reactions.
7-cell specialization
The favorite son. One cell divides into two but it is the same in each daughter cell, one containing more waste than any other, different protein concentration or lacks any component. These may have been the history of cell specialization. Currently occurs in bacteria, yeast or some unicellular algae and in some cases, live in colonies, where some individuals specialize in certain functions depending on their location within the colony. Specialization means greater efficiency. From there to cells such as neurons or white blood cells would be still a long way.
8-
sexual reproduction would we be without sex! It has been suggested that sexual reproduction allows rapid adaptation of species to quickly eliminate harmful mutations and spread the benefit. His appearance could be related to viruses and other parasites or as a byproduct of the strategy of doubling the genome to reduce the effects of mutations. In any case, sexually reproducing life forms have diversified and acquired a complexity that no asexual can be overcome.
9-embryonic development
"Nothing that happens in life you will mark you as much as gastrulation. The instructions to form a body in a gradual and orderly accounted jump a world of jellyfish and worms today. Instructions are grouped into blocks or genetic packages that allow greater adaptability. One way to highlight in embryonic development is gastrulation, which involves the invagination of a layer of cells of the embryo. So, at first glance not seem so important but its appearance marked specialization in 3D, as in most animals as us versus 2D specialization that occurs in worms.
10-The brain and nervous system
Long before the appearance of the nervous system cells communicate only through contacts with neighboring cell and the emission of signals such as hormones. In my opinion, the jump is not so much in the formation of a network to deliver faster signals but in a centralization of signals in the long run would be the appearance of the brain. The study of neural networks has advanced considerably in recent years thanks to studies in several animal models, especially in the worm C. elegans, we are aware of the network formed by its 302 neurons.
Source: TALL & CUTE
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