The CHAPTER 8. LIFE

Return  to a Fig. 6 and we shall be acquainted with milestones of development of the Earth. There are various approaches to a periodization of a history of our planet. From them main are the geological approach and paleontological. The geological approach divides a history of the Earth on lunar, nuclear and geosincklinal stages. 
       The paleontological approach divides a history of the Earth on a stage of chemical evolution and stage of organic evolution. A stage of organic evolution on criptozooan over-stage, when the one-cell-like organisms developed, and fanerozooan over-stage, when the multicell-like organisms, both animals, and plant developed. Fanerozooan over-stage is divided on paleozooan (ancient animals), mesozooan (middle animals) and kainizooan (modern animals) eras.
       Eras are divided on periods. Taking into account, that this book not the tutorial on paleontology, we shall not stay explicitly on the detailed definition of processes of development of an  ancient animal and flora. First of all we shall pay attention to those temporary scales, in which the processes of development of life on the Earth happened.
      In an extremity of lunar period, during volcanic activity, the plenty of diverse chemical junctions was created. Being dissolved in water, this chemical junctions forming so-called "primary broth", in which they performing the diversified chemical reactions. It is interesting, that the structure of this "broth" is close to chemical structure of alive creatures. The origin of life was promoted by appropriate physical conditions (pressure, temperature etc.), therefore  the reactions of polimerisation was possible. In an outcome of these reactions there were long polymeric molecules, which, among other things, were as though templates, because on that the similar molecules were formed. Thus there arose a processes of replication. At the expense of it the denseness of such molecules in a solution has increased, in this connection has increased also probability of origin both more complicated and more stable molecules. Thus there were premises for origin of life. The emerging of such molecules finishs period of chemical evolution. This period was lasting about a billion of years.
     To the finish of this period, in "primary broth" were available all component, necessary for origin first, rather primitive cells. Namely prototypes DNA, polipeptids, lipopeptids and other junctions, from which there could be shells of cells, albumins, DNA etc. And certainly, behind hundred millions years the cell simply could be derivated. And having appeared, during approximately three billions of years, the cell developed, was improved and began to have such kind with what we know now.
      Let's look at a cell (Fig. 9). It is arranged certainly not simply. At once such formation, certainly arise could not. Such cell is a product of long evolution. And  if to look more careful, at us the doubt in a correct of a title can appear that we see an one-cell-like organism. Really, into structure of a cell enter a nucleus, ribosomas, mitohondrias, lisosomas and other organellas (as them generally name). Quite creates an impression, that before us community of cells, integrated by common shell. Except for such, as is shown on Figure, exist a mass different other, that is much lesser than cells - bacteria, viruses, bacteriofags, plasmidas etc.
      There are cells, which have no nucleuses, there are such, which have no a cell-like diaphragm etc. But all cells have DNA. The truth and DNA are be different, for example is similar DNA formations called RNA.

It speaks that in process  hundreds millions years   formed every possible variant of molecules of alive cells. Some have appeared not so effective and for ever have disappeared. Some have appeared are useful to those or other functions and have taken its place in cells. The different cells had different destiny, some were integrated to erecting  more complicated cells, other was acquired such properties, which provided for they a possibility of a survival.               So the viruses have appeared for example. The virus has very short DNA. It has by an ancestor a cell, which has appeared at a very early stage of cell-like evolution. The processes in cells were differently organized also. One have acquired ability to use energy of light and so the one-cell-like seaweed has appeared, the ancestors of plants, mushrooms, blue-green seaweed, cells acquiring  a albuminius molecules, which at first consumed them from an environment, and then seizing other cells. There are even cells fed by various minerals.
        Thus, the early history of development of life, is rough process of casual cuts and tries, process of fast mutations and natural selection in a huge biomass of one-cell-like entities. You see and now biomass of one-cell-like organisms is more, than all remaining alive entities.

But a main rod of existence of cells (as well as all alive) is the duplication or, as we spoke, replication. And, if at an early stage of origin of life the duplication by copying (that is replication) was property of an alive substance generally, with origin of the elementary cells it became property main, but not of a unique molecule of a cell - DNA.
      What such DNA. It has a structure similar to a rope ladder, that is curled in the right spiral (Fig. 10). It reminds a corkscrew, but corkscrew double. Nitrogenial molecules in four kinds   in sequences which the genetic information is made, are named nucleotidas also are similar to one from them - тиминмонофосфат, shown on a Fig. 11. In total them four and they are designated by the letters - A,T, Г and Ц. And, in one cross-beam them two, connected on a principle komplamentarity, or supplementarity: against A should be Т, against Г should be Ц.
      On a photo 15 the model of a site DNA and on a photo 16  a photo of it executed with the help of electronic microscope is shown.
      In the certain conditions the parallel chain DNA can be divided, and on each from them the new chain can be going. On a photo 16 it is visible, as on extremities DNA is divided on two chains. Thus also a replication  is carried out . If a chain short, this process not very much is complicated, but if it is long, there is a mass of complicated mechanisms, with the help of which is carried out the replication. We shall not go deep into this problem. We have enough of to understand, that origin of process  replication could happen and by the natural way.
                     More over, if appropriate conditions is such process should arise as inevitable. That is, the origin of life is not probability process. The probabilities in origin of life consists in a probabilities of origin of appropriate conditions.

From the moment of origin of cell-like life before shaping multicell-like has passed about three billions of years. 

To this period correspond Arhean and Proterozoian eras. How appeared multicell-like forms of life. First of all we shall tell, that the origin of the multicell-like forms of life is natural and regular process. Really, the one-cell-like organisms, being multiplied, as a rule remain there, where have appeared, forming colony. The conditions at centre and on a colony rim essentially differ. It could reduce that during the adaptation to these conditions the certain specialization of separate cells has appeared. And the specialization in cell-like community also is, purely, origin of multicell-like organisms.

Multicell-like organisms. In origin of multicell-like organisms a large role have played one-cell-like and meaning that they promoted a significant modification of the physical factors on a planet. First of all, in transformation of primary atmosphere in nitrogen-oxygen. The main role belongs to a photosynthesis, which has changed a biosphere, as the oxygen bore in itself huge stocks of chemical and biochemical energy. The majority of chemical processes which are flowing in a nature is connected to oxygen: formation  of a ozone stratum in atmosphere, development of a biosphere, accumulation organogenian rocks.
      On the last datas, already in an extremity arheas, except a bacterias and one-cell-like seaweed, begin to occur and multicell-like seaweed, and  primitive multicell-like organisms.
      In an extremity  of  proterozoan era there were only water animals and plants. In the seas the medusas, worms and soft corals were distributed. The heyday of multicell-like organisms occurs in fanerozoan, which divide, as we spoke, on three era: paleozoan, mesosoan and kainozoan together during approximately six hundred millions years. It is much less, by the way, than time, during which the one-cell-like organisms reigned.
      In the organic world  of kembrian period, beginning paleozoi, occur arheociats(Fig. 12) and most ancient  trilobits (Fig. 13), brahiopods, stromatoporoideas. In ordovical and selurian periods there are first without-jow fish-look-like organisms. To an extremity selurian the role trilobits is reduced, there are new kinds of corals, brahiopods, first present  a jow-fish. An extremity selurian - time of an exit on land of maximum of plants, first of all psilophitas. Spreading of a ground plants was the important step in a conquest of a land by animals.

In devon have received distribution  ammonits and belemnits (Fig. 14),the large crawfishes,  descendants of trilobit, fishs.  Rather  broad distribution in devon the ground vegetation has received. It first of all riniophits, which heyday was on middle devon. To an extremity  of devon epoch riniophits flora dies out, on change to it come fern-like and  some representatives naked-seeds plants.  Before emerging of man about Three  Hundred of millions years .
       The ground plants occupying humidified seaside flatnesses, bogs, shallow reservoirs are most typical of flora carbon. It ferns, naked-seeds plants, etc. In upper carbon occur coniferous.

The fauna carbon on a comparison with devon differed by large diversity of animals. 
     Occur and achieve large variety (more than 1000 kinds) insects, including large, in a big way of wings up to 70 sm. From vertebrates the fishes, especially shark-like lived in the seas. The amphibians represented by stegocifals, similar to lizards, the snake, crocodiles, length  they have about 2 meters. On the average carbon there are first reptiles, among which were predatory, plant-eaters and insect-eaters.

The processes of development vegetative and fauna were accompanied and were largely determined by a modification of a climate. 

The modification of a climate, in turn, was determined as a modification  of tectonikal  processes, as the gravitational differentiation approached to the completion, and movement of continents. In particularly, that Antarctic Continent has taken its  place on a South Pole, the movement of ocean currents became hampered also climate became more contrast.
     In connection with broad distribution of deserted landscapes in the Perm period the amount of moisture-loved plants is reduced. Their place take  of a naked-seeds plants plant: coniferous, ginkgas etc. The essential modifications happen in structure of marine and ground fauna. To an extremity perm the four-radial corals, some tabuliats, die out trilobits, and many other ancient animals was disappeared. The amount  of cartilage fishes is sharply reduced. Alongside with it the reptiles are widely distributed, and, if their one branch has given a beginning to ancestors mesozoan of reptiles, other has features of a likeness with the first mammals. The extinction to an extremity paleozoy of majority of kinds  of paleozoan organisms was stipulated, apparently, both general laws of evolution, and modification of conditions of existence. So, occured mesozoy. Before our time remained Two hundred fifty millions years.
                In the organic world trias, first period of mesozoy predominate  of the mesozoian form, but at the same time still essential role was played by the representatives paleozoian  fauna and flora. From marine forms are characteristic  a fish ,the reptiles - ihtiosaurus (Fig. 15) and plesiosaurus (Fig. 16).  Vertebrates of a land replenish with dinosaurs - brontosaurus (Fig. 17), tarbosaurus (Fig. 18), triceratopsas (Fig. 19), protoceratopsas (Fig. 20), stegosaurus (Fig. 21), saurolofas (Fig. 22), pinacosaurus (Fig. 23) etc. The reptiles master air space, in the beginning of jrasik period occur pteranodons (Fig. 24), sordeses (Fig. 25), longiscvams (Fig. 26). The role of amphibians of a gradually is reduced. In an extremity  of jrasik period there are mesosaurus (Fig. 27), first birds, for example arheoptericses (Fig. 28) and first mammals, like triconodon (Fig. 29). Among plants in jrasik period dominated naked-seeds plants.
       During of chalk period the organic world of the Earth is essentially changed. Already in the beginning  of early chalk epoch occur  of a seed-covered plant, which to an extremity of period completely displace naked-seeds plants, and the flora acquires appearance  of cainozoan era, in which we and live.

Fig.15 Fig.16 Fig.17 Fig.18 Fig.19 Fig.20 Fig.21 Fig.22 Fig.23 Fig.24

Fig.25 Fig.26 Fig.27 Fig.28 Fig.29

        To an extremity of chalk period the large dinosaurs die out. The further development is received a birds, mammals,  fish. Frequently fact of extinction of large dinosaurs as some mystery have imaging. However, it is necessary to take into account, that the process of their extinction proceeded millions years. The reasons, generally speaking not so also are mysterious.
                      At first, this time, when on change  to naked-seed-plants come covered-seed-plants. Their foliage considerably more rigid, than at earlier kinds of plants. The physiology  of dinosaurs could not adapt to new food.
                      Secondly, the climate became more contrast. By night cold of a reptile stiffen and become easy prey  of warm-blood animals.
                      Thirdly, at large dinosaurs and eggs are large. The dinosaurs could not to hide and to protect them, especially at night, therefore warm-blood mammals ate they.
     Besides not so they also have died out. And now we see them as javan varan, for example, which on magnitude is more the cows, crocodiles and large anaconda. Besides the variety of kinds, after vanishing large dinosaurs, not only has not decreased, but even has increased. Their posteritys are a birds, and a mammals, and we at last.
      The cainizoians era began about 67 mill.ears ago. The structure terrestrial crust was close to this time to modern. The extensive territories took ancient and young platforms,  the geosinclihalien mode was saved only on separate sites Mediterranean and Pacific  belts, were formed modern Atlantic, Indian and Northern  oceans. However outlines of continents was differed from modern. Eurasia and Northern America incorporated by a land in region of a Bering strait, the cross connection existed between Africa and Southern America. Australia, Antarctic Continent, and is possible, and Indostan represented a unit.
        The cainizoian era is subdivided on Paleogen (67 - 25 mill. years), neogen (25 - 1  mill. years) and antropogen periods. As it was already marked, on the boundary mesozoy and kainozoi the sharp updating of fauna happens: a ammonits, belemnits, large reptiles die out . The heyday  of fishes, mammals, birds occurs. The flora represented in main by cover-seeds. On land the mammals dominate, among which are selected predatorys, hoofed, trunked, the primates, and a little bit later rodents. The reptiles play a modest role and in main represented by the modern forms.
     To an extremity of paleogen the ancient primitive predators and hoofed die out. In neogen there are ancient kinds of bears, hyena, rhinoceros, dogs, giraffe, anthropoids, and to an extremity neogen in main all modern animals.

Fig. 30

And at last, antropogenias period. A mainest feature  of antropogenias period is emerging the man. The second feature antropogenias - it a small duration and that it not finished. The broad distribution continental freezing is characteristic also for this period, in connection with which the oscillations of a level of global ocean happened. These modifications resulted in emerging new kinds of animals adapted to a cold climate. Such as mamonts, deers etc. The part from them has died out by of consequent heating.
      Thus, from time of emerging of life on the Earth, it developed continuously. Neither natural disasters, nor the internal reasons could not stop it. Volume of a biomass, amount of kinds of animals and plants was constantly increased, attended  new ecological niches, the mutual relations between kinds and inside them became complicated, has increased complexity of a structure of animals and plants. The general stream of life (animals) is shown in a Fig. 30.
        Presumably total number of nowadays living kinds of plants and animals, apparently, reaches not less than 1,5 millions. From them on a share of plants it is necessary about half of million. The kinds rather fast vary. If a conditions inhabiting of a kind (ecological niche) is changed, the kind can acquire new specific indications, in natural conditions, literally for hundreds years. On such background is appeared a man.

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