Evidence of Early Life
Earth and the solar system itself estimated 4.6 billion years old. Meanwhile, the earliest time of formation of life on earth is estimated to appear about 4 billion years ago. This caused a lot of asteroids and comets with the earth from the heavily bombarded during the formation of up to 4 billion years ago. Scientists know about the earth that broken because they see no conflict of locations on the moon that are not covered by erosion, as well as on earth. Given the size of the valley in a collision in that month, then certainly that asteroids and comets that strike in the initial formation of the earth is very big. Once the size, until the energy released when colliding with the earth's surface causes the increase in ocean temperature until it boils and evaporates. This is the condition which causes the planet uninhabitable because somehow water is essential for life.
Scientists from the Scripps Institution of Oceanography in San Diego, California, reported in November, 1996 in the journal Nature that the carbon composition of ancient rocks from an island in the vicinity of Greenland indicate that the process of life began about 3.8 billion years ago. Ancient rock near Greenland is believed to no older than the rock formations of Greenland, known as the Isua Formation, consisting of the oldest sedimentary rocks are decomposed by water. Radioactive dating indicates isua 3.8 billion years old. (Radioactive dating using the rate of disintegration of the radioactive element properties to estimate the age of the sample)
Indirect evidence for life found on this rock is a clear distinction between light isotope ratios with a heavier isotope. Isotopes are atoms that have a common set of number of protons but differ in the number of neutrons, giving each a different isotope of atomic weight. (Sum of protons and neutrons). Rocks studied by a team from Scripps contain more carbon-12 are estimated to come from non-biological processes. Living organisms tend to be less like elements of the lighter isotope than the heavier. Therefore, organisms use carbon - 12 more often than carbon - 13 (which contains one extra neutron), and oxygen - 16 compared to oxygen -18. (Which contains two additional neutrons)
The first direct evidence of life on earth that is the discovery of the oldest fossils, dating from 3.55 billion years ago. This fossil consists of microscopic sections, the degraded cell wall cylindrical or elliptical-shaped fused. The line outside the cell wall is preserved in rocks in the form of a thin sheet of carbon-rich.
Thus, fossil evidence indicates that life began about 3.8 billion to 3.55 billion years ago. Geological evidence to prove that the earliest forms of life must have evolved first in the absence of oxygen molecules in the atmosphere. Few traces of free oxygen in the atmosphere 4 billion years ago. Evidence of the lack of oxygen is in sedimentary rock, such as sand, clay, and chert are buried deep in the ocean in the early formation of continents, which are now in the territory of Australia, South Africa, Northern Canada, and Greenland.
Some of these ancient rocks found in large quantities in the form of iron compounds than in marine sediments. The water current that keeps sediment rich in dissolved oxygen, and iron when exposed to oxygen would quickly rust, in a process called oxidation. Rust is not soluble in water. In fact, iron is not oxidized soluble and move into the ocean following the river flow. Very few traces of oxygen can cause the iron to separate from the water (precipitation) and fell to the bottom of the ocean, without changes to rust. Iron in large numbers found in ancient sedimentary rocks to convince us that very little oxygen in the initial formation of the earth, whether it is in the atmosphere or dissolved in the ocean.
Primitive Bacteria: Living Fossils?
Most primitive organisms, which exist today are bacteria that live in the area and the blast of hot water on the ocean floor where hot water flows originating from volcanic activity. Relatively recently, scientists believe the significant role of this organism in the evolutionary process.
The discovery of these primitive organisms makes possible the development of new techniques of biotechnology in recent decades to allow scientists to determine the order sheets of the genetic code of organisms. Scientists then can estimate the amount of change in this code. Based on the assumption that organisms carry more genetic code in its body that handed down by ancestors-ancestors. It is possible to put together to suggest a link with the evolutionary process called "tree of life".
The results of genetic comparisons showed that living organisms, including in 3 basic groups, called domains. Domain of a living being that is, consists of:
v eukaryotes: organisms whose cells contain the genetic code; animals, plants, fungi, algae and protozoa.
v Bacteria: single-celled organisms that do not have a cell membrane.
v Archaea: a single-celled organisms, microscopic. Biochemical differences with the bacteria.
Bacteria or the most primitive archaea have two unique characteristics. They Autothrops, meaning able to make its own food, synthesize complex molecules using chemical energy they captured from the outside environment. This is very surprising, because at that time many scientists believed that the first living organism is heterothrops (organisms that absorb the complex molecule as a food rather than mensintesisnya). Animals are heterothrops, while green plants, cyanobacteria, such as bacteria and arcahea primitive, is autothrops.
Primitive Autothrop quite different from green plants and cyanobacteria in how they synthesize complex molecules. Green plants and cyanobacteria absorb energy from sunlight, CO2, H2O, and O2 to synthesize complex molecules. Meanwhile, organisms such as Archaea that live near hot springs absorb the energy of chemical substances such as Hydrogen Sulfide (H2S) that came out of the volcanic vein to make complex molecules (compounds containing carbon).
The fact that the most primitive organisms that live today in very hot environments, concluded that life, or at least the embryo's life may have originated from there.
4 billion years ago, surely there are many veins in the volcanic ocean floor than today. Scientists believe that the early formation of the earth there are many piles of radioactive atoms. Some of the radioactive atoms are fused into non radioactive substance on earth, removing the heat when it exploded.
Explanation and Statement of Life
To learn more about life originated, then we would need a definition of "life" itself. Many scientists agree that a living thing must have 2 things;
metabolism and reproduction. The first, was living organism metabolism, which absorbs energy from the environment, save energy in the form of complex organic molecules such as carbohydrates and then turn it into energy. Energy from the outside can be shaped light or chemical energy, as in the case of green plants and archaea, or, heterothrops like humans and animals, in the form of food.
Various chemicals formed and changed in the metabolic processes of living things. This earthly life are derived from chemical reactions that include carbon molecule, called an organic chemical reaction. Chemical bonds between carbon with oxygen, nitrogen, hydrogen or other organic molecules is weak when compared with other chemical bonds. Weak chemical bonds which means that organisms can easily arrange the structure of complex molecules, or even break it down when needed. Heat, light photons, radioactive energy is a substance that can easily change the structure of carbon.
The second definition of life is reproduction. All life on earth involves 2 molecules - deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) - as the draft-Basic reproduction. DNA and RNA is the most complex molecules from the organism. Without his presence, the organism will not be able to make a replica of itself. Both have the form of a very long, spiral staircase and has 6 basic components that are repeated throughout the molecule; Sugar, Phosphate, and 4 nucleotida basis. Nucleotide that forms the basis of this pair of ladder rungs of the DNA spiral. This series of nucleotide base that carries the genetic code of organisms.
When a reproduced cell, its DNA into the cells replicate themselves, and lead to splitting of cells, with each of 2 cell receives one set of DNA. Series of DNA determines which proteins are made in the cell, and in what form they are made. RNA, like DNA molecules, translating instructions contained in the DNA and pass instructions to the appropriate place within the cell to build protein.
Proteins - organic molecules that can be very long and complex - is one important component of the organism. Such as DNA and RNA, proteins consists of several important components that are repeated in a long chain. The basic components are known by the name of Amino Acids. More than 20 amino acids that form the basis of proteins in an organism. There are proteins called enzymes - proteins that speed up chemical reactions in the body of organisms.
When the DNA and RNA to make a replica of himself, the replicas are not always perfect. Sometimes a mutation - a change in the genetic code. This mutation is important in the evolution of life because sometimes these changes which refers to a characteristic of organism survival or reproductive condition more quickly. In this process, called natural selection, organisms that have characteristics that match will escape and reproduce quickly to establish its existence.
The essential thing is more to life Tues All living organisms are made of a set of cells. Unless the virus. A collection of cells, "factory-organic" that build molecules that are more complex than the more simple, coated by a membrane / membrane wall made of organic molecules. Cell membrane is what allows the transport of molecules into and out of cells.
Origin of Life Theories
Even within any one-celled organisms, the molecule - complex molecule take part in various chemical processes that define life. The development of the most primitive organisms that alone requires many steps. First, organic chemical "base-building" life, such as amino acids, would have been available from one source. Second, the "base-building" are somehow became longer and longer, more complex, and at one point, the DNA will be formed. This complex organic molecules somehow be inside the cell. In recent decades, scientists have learned a big gamble on the above steps and developing into a new theory about where, how, and in what form life first will develop.
Basic theory of the first modern study of the questions were developed by Russian chemist, AI Oparin, and Genetic Expert UK, J.B.S. Haldane, in the 1920's. Openly, they contend that the organic material basis of life-development can also be formed from more simple molecules of the primitive Earth's atmosphere - the atmosphere without oxygen molecule - when energized by lightning or other similar energy,
Referring to the hypothesis of Oparin and Haldane, complex organic molecules formed in the atmosphere, will go down in the form of rain into the ocean primitive, form the "organic soup". Two scientists reasoned that when the molecules come together into the soup, natural selection would work in the form of a set of molecules that eat other molecules to chemical energy, growth, and reproduction. Then, Oparin and Haldane concluded that life originated from a simple heterothrop - the cells that feed on other organic material. Only when it became vacant organic soup of organic molecules, then the primitive forms of life will collapse by mutation into autothrop and began to absorb physical energy, not chemical energy, to make organic molecules.
The first part of Oparin and Haldane's ideas were tested by chemist Stanley Miller beginning in the 1950s. Then, by a graduate who is under the direction of Nobel laureate Harold Urrey physics, University of Chicago in Illinois. Using Jupiter's atmosphere which is then believed to be a primitive planetarium atmospheric model, miller put a mixture of methane (CH4), ammonia (NH3), water vapor (H2O) and hydrogen (H2) into a series of bottles connected by enclosed glass tube. He made the series such a way so that he can send a flash of electricity through one of the bottles, simulating lightning in a primitive atmosphere.
The result is surprising; flow of electricity that is released causing the gas to react to form a set of organic molecules is quite complex and began to fall like rain in the artificial atmosphere. Among these molecules are molecules-amino acids, basic life-building of proteins and so is all life. The initial part of Oparin and Haldane's hypothesis - that the foundation-building that made life in the early atmosphere is due to the presence of lightning or other similar energy sources - seems closer to the truth.
Miller and other scientists continue their experiment to determine where, and how the basic form of life-development. These scientists showed that the organic material can be made from many kinds of energy, ultraviolet light (as the sun), heat (as volcanoes), and even shock (as meteorite collisions.) Their experiment has been producing about 20 amino acids, the synthesis of life that exist today such as sugar and phosphate backbone of DNA and RNA.
Even so, there are parts of Oparin and Haldane's hypothesis that is in question for years. For example, the most primitive organisms known that they are not heterothrop autothrops - that is, they do not eat other molecules for energy, as predicted Oparin and Haldane.
On the other hand, scientists now believe that the initial composition of the atmosphere quite different from the mixture used in Miller's experiment. Miller gas mixtures and other spray gas into the bottle is the reduced height (a state of chemical that is the opposite of oxidation). Geology and theoretical studies in recent decades has reached the conclusion that the earth is rapidly losing the primitive's it: the atmosphere of the reduced height.
At the end of meteorite bombardment around 4 billion years ago, most of the earth's atmosphere may contain N2, CO2, water vapor (H2O), and a number of carbon monoxide (CO) - with a mixture of different elements that are used Miller-Urey. Miller-Urrey experiment with the gas mixture does not explain the abundant quantity of basic life-building.
Organic Matter from Space
These years, most scientists agree on a consensus that the basic life-building came from outer space. Spacecraft with a mission to see Halley's comet discovered an abundance of organic matter in space. In fact, Halley's comet body (other than a glowing tail and corona), is a darkest object ever observed in the solar system: covered with organic mass. As well as the moon from the planet Jupiter and Saturn. Therefore, it seems even the synthesis of organic molecules studied by the Miller-Urey experiment could not have happened at the beginning of the earth, it could happen elsewhere in our solar system, including comets.
Experiments and calculations updated, including those conducted by astronomer Carl Sagan of the University Ithaca, New York, demonstrates that a fairly complex organic molecules such as amino acids, can survive in the event of collision comet to Earth. Then, the meteorite that fell during the end of meteorite bombardment believed to have imported the basic ingredients of life-development.
Establishment of an information-carrying molecule
The results of the above conclusion still can not explain the question of how DNA and RNA can occur. How can the information-carrying molecule that is so complex as it can come from processes that are not "live"? The biggest questions about life began: how DNA, or its predecessor molecule, can control and factory-organic produce is called a cell.
Scientists focus his hypothesis by assuming that RNA came first rather than DNA. DNA is not much to do nothing except save the information. In a cell living organisms, other molecules such as enzymes made of DNA reveal the information they carry. That information was then translated by the RNA molecule and then do what has been instructed DNA somewhere within the cell.
RNA not only impart information but also stimulate or to catalyzing chemical reactions that produce proteins. In all life today, RNA can not stimulate the chemical reaction alone, he was assisted by an enzyme known as Coenzim. Coenzim this is what has helped enzymes share the information during the reproduction of cells in a continuous chain from time to time.
One scenario that emerged recently - based on the idea of primitiveness "RNA World" - that life originated from a molecule that is always selfish to develop themselves. Molecules are always concerned himself first could have a simple form that only RNA nucleotide consists of short-chain hypothesis concerning the initial RNA molecule capable of catalyzing chemical reactions, taking the base-construction life of the surrounding water, and use it to reproduce itself. When sudden changes - mutations - in one molecular structure, primitive RNA will do something to address this change by accelerating RNA reproduction, as compensation for increasing the number of molecules that are mutated.
The scenario is not unreasonable. Now, viruses and bacteria repeatedly mutate and evolve more quickly become more resistant and immune. The average bacterium is able to reproduce itself every 20 minutes an appropriate environment, and the initial RNA is much more simple when compared with live bacteria is the most simple ones. Time to reproduce was estimated that only in units of seconds.
The concept of the selfish molecules gives important meaning in the reproduction and evolution. Oparin ideas, Miller, and Urey about metabolism - come together and provide an explanation of how a molecule that can get energy from other molecules.
Finally, if an RNA and enzymes that help her begin to synthesize molecules that form the cell wall to protect himself from the outside world diversity, RNA and then will increase this number even more. So then something called a life will emerge.
The life that started from the area around the heat flow in the water will make the perspective of the evolution process becomes more reasonable. Organic chemical reactions go faster in a hotter environment, then the errors in the genetic reproduction will often occur. Then, in an interval of time, more mutations that occur will make more complex molecules aggregate as compared with the lebh cold water. These mutations accelerate the process of evolution.
Where DNA plays now? DNA is the molecule that are stronger than RNA. DNA is unlikely to be destroyed by heat, ultraviolet light, or an error in a chemical reaction. Then, when the "RNA world" will become increasingly complex mutation, in a period of DNA would be useful to store important information about the discovery of molecules. DNA had been instrumental in maintaining the function of the molecular information stored for the better, so the mutation will run slower.
Life from outer space?
Another idea that emerged is that life originated not from earth but comes from somewhere in our solar system which is then transported to our planet. This idea is not only nonsense; most primitive bacteria like archaea are able to survive in an extreme environment and there is a possibility he will survive when they have to wade outer space.
In 1996, NASA reported a weak evidence that life has formed 4-5 billion years from metorite on Mars.
If evidence is true, then scientists should seriously consider the possibility that life on earth came from Mars. Mars has less gravity than Earth, making the rocks will more easily thrown into space, than fall back to the ground. Furthermore, because the earth has a strong gravity, causing the possibility of the earth to catch meteors than on Mars. We all may have come from Mars.
Of course, everything is still a possibility, and perhaps still is the possibility of life seemed to be formed just like that on Earth and on Mars. Especially when the comet that is rich in organic matter hit the planet 4 billion years ago.
Resolution of these questions will come from:
1. Chemical experiments on an ongoing basis against the carrier molecule-life,
2. Planning for exploration to Mars to study the fossils that were there,
3. And continue the search for regular sources, radio signals from outer space life. The findings confirmed that the signal will have a life somewhere along the line and explain that life will just show up unexpectedly
