Life … On Earth, it seems to swarm and occupy the entire surface, even the most extreme areas with almost impossible climatic conditions. Yet what seems so natural … is a small exception that for now, and I stress this term, we have not seen anywhere else.
Before seeing how this exception is life have appeared on our planet already see how to define it. After all, what is life?
Life in general is an explorer in a world hostileElle defined as the character of beings capable of evolving in an eco-system and an environment. With the particularity to grow, reproduce and therefore replace assimilation of elements such as air, water, food in general, atoms and small molecules constituents. Life is plant and animal, it can not be bottled under this definition. Note that all known living things have a finite life, and none are “immortal”.
Let us return to the beginning, the Earth as seen in the previous article is born there are 4.55 billion years, as the environment was very chaotic and hot, it will take hundreds of millions of years for the beginnings of life appear. Current estimates are starting life in its simplest form, prokaryotes (single-celled bacteria having no core), there are 3.8 billion years.
But how did we go from inert matter to life? By what “miracle”? Creationism and neo-creationism are not in any way credible answers on the matter. The first being the literal view of Genesis contained in the Old Testament or the Koran, addressing the creation of the world and of man. In summary, the Earth, the Sun, the Moon and all life were created without evolution of species there are about 10 000 years. The second is a very interpreted version of the same text, to make it less literal and try to stick a little to the evolution of species as well as modern cosmology, but always seeing God’s work with us to create specific (anthropocentric vision). This leader evolution and leaving no room for chance mutations.
But back to the subject so with a scientific approach. Despite the advances of science on the subject, this issue is so complex, even today, we do not have total certainty. But we have models with more or less likely to be good. We can consider that there is the model “first gene” and the model “metabolism first”. The second was developed before the discovery of DNA, therefore it gradually abandoned in favor of the first, although some still try to bring water to his mill. The latter will therefore not be discussed in this article.
simplified diagram for understanding RNA structure / ADNRevenons therefore the model “first gene”, again, it is divided into two predominant assumptions, which could be combined:
– The first is the development of life in the hot springs of the ocean. What we call the formation of RNA in the “primeval soup” landed.
The aminés1 acids would have combined to arrive at a structure “messenger” RNA, which means ribonucleic acid molecule present in virtually all living beings. Two pairs are the first manifestations of these combinations resulting in life: AT (adenine – uracil) and CG (cytosine – guanine). The fifth amino acid, which may have been entered, the “T” (thymine), come into play in the DNA by replacing the Uracil to form the A-T pair.
– The second is the Panspermia, a theory dating back to antiquity but modernized by Hermann von Helmholtz in 1878. This term contribution this cache, once again, of comets. They have already made a lot of water on Earth, but they could also have them bring life. With RNA or even prokaryotic already formed and trapped in the cometary ice.
Nevertheless, this is the first that the preference of the scientific community. The other is often used neo-creationists purposes.
These simple structures will be painfully slow progress in eukaryotes, ie multicellular units with cores. Prokaryotes having appeared there 3.8 billion years, it will take 1.7 billion years (therefore -2.1 billion years compared to today) to really see this development and therefore eukaryotes spread.
A time shorter half must elapse for life explodes diversity and multiplies the living forms and organisms. Between -528 and -510 million years, so the Cambrian explosion, which also appoint the ‘Wildlife Burgess “in relation to the site where was found an enormous diversity of arthropodes2 to brachiopodes3 of trilobites4 and sponges or algae.
An anatomical disparity as some paleontologists and biologists believe that she has never again been equaled, and is the origin of the different organization of current cash schemes. And yet … life was not even out of the water. This new development will there -430 million years, bringing the dinosaurs 200 million years later.
These companies will dominate the Earth, almost unchallenged, and the first small mammals will rub shoulders with some 70 million years later, will have to hide. It is the great extinction Cretaceous ago 65 million years ago that mammals will have their chance to dominate the terrestrial environment.
If two theories are initially confronted to understand the end of these behemoths that ruled the roost today it is commonly accepted that the cause is a gigantic nuclear winter, resulting from the impact with the Chicxulub meteorite. Strata “black”, impregnated with abnormal levels of iridium testify to the transition Cretaceous – Tertiary, as the crater that gave the name to the space object responsible for the disaster in Mexico. https://www.youtube.com/watch?v=Y8Ij9xboreA&nohtml5=False
And the man ultimately in?
The existence of the Earth with its biodiversity 24hLes first hominids appear that there are about 7 million years … or almost nothing on the scale of the Earth. And if we bring Homo sapiens, ie modern man … our presence seems even more ridiculous. Imagine that since the formation of the Earth, until today, does not in any one day of 24 hours. We would be born by respecting the time scale, at 23:59 and a few seconds …
Therefore, man is born a new fresh on Earth. Looking good the whole process of emergence of life, until we, homo sapiens, we have the right not to respect nature? Or rather we have a duty to accompany and protect it while continuing to evolve in it for maybe one day go elsewhere … life without being forced?
Humanity to protect itself, to protect life généralMatthieu Votta
1 – amino acids: molecules that go into the composition of proteins by their connections with what are called peptides, proteins are macromolecules performing various functions breast living cells of an organism.
2 – arthropods are the branch of the animal kingdom with the most living species, crustaceans, insects are included. These are invertebrate animals having a rigid shell and jointed legs.
3 – brachiopods are the “mollusk” branch of the animal kingdom, have experienced great success, today there are only a small part of biodiversity.
4 – trilobites are a specific class of arthropods, they have completely disappeared at the end of the Permian there are 250 million years.
– “was he was the world created in seven days? “Pascal Picq – paleoanthropologist at the Collège de France
-” A Brief History of Time “and” there he has a great architect in the Universe “by Stephen Hawking – Mathematical flesh Cambridge cosmologist
– Wikipedia on the origins of life on Earth: https://fr.wikipedia.org/wiki/Origine_de_la_vie
– “once upon a time life” in a nod to this beautiful cartoon passing on the public channel (FR3) from in September 1987 after a brief stint on Canal +. This taught children the basics of how the human body.