Life development on the Earth during a protean era

Evolutionary development of organisms is investigated by variety of the sciences considering different aspects of this fundamental problem of natural sciences. Fossils of animals and plants existing on the Earth during the last geologic epoch, are studied by paleontology which it is necessary to put on the first place among the sciences directly bound to research of organic evolution. Studying the residual of ancient forms and comparing them with extant organisms, paleontologists reconstruct shape, a mode of life and related communications of the died out animals and plants, define time of their existence and on this basis recreate phylogenesis - historical continuity of different bunches of organisms, their evolutionary history. However in solution of these challenges the paleontology should lean on given and conclusions of many other things of the sciences concerning a circle of biological, geologic and geographical disciplines (the paleontology, studying fossils of organisms, is as though on a biology and geology joint). For understanding of conditions of life of ancient organisms, in a fossil state the paleontology uses definitions of time of their existence and laws of transition of their residual data of such sciences as historical geology, a stratigraphy, paleogeography, palaeoclimatology, etc. On the other hand, for analysis of a constitution, physiology, a mode of life and evolution of the died out forms it is necessary to lean against detailed knowledge of the conforming parties of the organisation and biology of nowadays existing organisms. Such knowledge is given first of all by operations in the field of a comparative anatomy. One of the primary goals of a comparative anatomy is the establishment of homology of members and frames at different kinds. The homology is perceived as the resemblance based on relationship; presence of homological members proves direct related communications of organisms possessing them (as ancestors and descendants or as descendants of the general ancestors). Homological members consist from similar of elements, educe from similar embryonal germs and occupy similar position in an organism. The functional anatomy educing nowadays, and also relative physiology give the chance to approach to understanding of functioning of members at the died out animals. In analysis of a constitution, ability to live and conditions of existence of the died out organisms scientists lean against the principle of an actualism put forward by geologist James Hutton and deeply developed by one of the largest geologists of XIX century - Charles Lyell. According to a principle of an actualism, law and the interrelations observed in the phenomena and objects of the inorganic and organic world in date time, reacted and in the past (and from here “the present is a key to past knowledge”). Certainly, this principle is an assumption, but, possibly, it is true in most cases (though always it is necessary to take into consideration possibility of any originality in course of those or other processes in the past in comparison with the present). The paleontologic annals presented by fossils of died out organisms, have gaps, sometimes very large, caused by specificity of conditions of a burial place of the residual of organisms and an extreme rarity of coincidence of all factors necessary for it. For a reconstruction of phylogenesis of organisms in all completeness, for reconstruction numerous “missing parts” a pas a parentage tree (a phylogenesis graphic representation) purely paleontologic data and methods appear in many cases insufficient. Here the so-called method of threefold parallelism introduced into a science by known German scientists Hackel and based on comparison of paleontologic, relative anatomical and embryologic data comes to the aid. Hackel started with formulated by it “the basic biogenetic law”, saying, that the ontogenesis (individual development of an organism) is the cramped and reduced repetition of phylogenesis. Hence, analysis of individual development of modern organisms allows to judge in any measure a course of evolutionary transformations of their far ancestors, including not remained in paleontologic annals. Later Severtzov in the theory of phylembryogeneses has shown, that an ontogenesis and phylogenesis interrelation is much more complex, than considered Hackel. Actually not the phylogenesis creates individual development (new evolutionary acquisitions extend an ontogenesis, adding new stages) as believed Hackel, and, on the contrary, hereditary changes of a course of an ontogenesis lead to evolutionary rearrangements (“the phylogenesis is ontogenesis evolution”). Only in some special cases when evolutionary rearrangement of any member descends by means of change of serotinal stages of its individual development, i.e. New signs are formed in the end of an ontogenesis (such method of evolutionary rearrangement of ontogenesis Severtzov named an anaboly), such interrelation between an ontogenesis and phylogenesis which is described by biogenetic law Hackel is really observed. Only in these cases it is possible to involve embryologic data for phylogenesis analysis. Itself Severtzov has given interesting examples of reconstruction hypothetical “missing parts” in a phylogenetic tree. Analysis of ontogeneses of modern organisms has also another, not less important for analysis of a course of phylogenesis value: it allows to find out, what changes of an ontogenesis, “creating evolution”, are possible, and what - are not present, that furnishes the clue to understanding of concrete evolutionary rearrangements.

For understanding of essence of evolutionary process, for causal analysis of a course of phylogenesis conclusions evolutionistic - a science named also the theory of evolution or Darvinism, by name the great founder of the theory of natural selection Darwin have the most paramount value. The evolutionistic studying essence, mechanisms, the general laws and directions of evolutionary process, is theoretical base of all modern biology. As a matter of fact, evolution of organisms represents the form of existence of living matter in time, and all modern exhibitings of life, at any level of the organisation of living matter, can be perceived only taking into account evolutionary background. That substantive provisions of the theory of evolution for analysis of phylogenesis of organisms are to a great extent important.

The listed sciences at all do not exhaust the list of the scientific disciplines involved in analysis and analysis of development of life on the Earth during last geologic epoch. For understanding of a specific accessory of fossils and transformations of kinds of organisms in time systematisation conclusions are extremely important; for analysis of gang of faunas and floras in the geologic past - the given biogeographies.

The special place is occupied with questions of a parentage of the person and the evolution of its nearest ancestors having some specific features in comparison with evolution of other higher animals, thanks to development of labour activity and a sociality.

Scales of Geologic Time

Studying evolution of organisms, it is necessary to know about its course in time, about duration of those or its other stages. Historical sequence of formation of sedimentary soils, i.e. Their relative age, in the given area is established rather simply: the soils which have arisen later, were deposited atop earlier seams.

Conformity of relative age of seams of sedimentary soils in different regions can be defined, comparing the fossil organisms which have remained in them (the paleontologic method which bases have been gobed up in the end of XVIII - the beginning of XIX century by operations of English geologist U.Smith). Usually among fossil organisms, characteristic for each epoch, it is possible to secure some the most customary, numerous and eurysynusic kinds such kinds have received the name of supervising minerals.

As a rule, absolute age of sedimentary soils, i.e. The time interval which has driven since time of their formation, directly to establish it is impossible. The information for definition of absolute age contains in igneous (volcanic) soils which arise from cooling down magma.

The absolute age of igneous rocks can be defined under the maintenance in them radioactive of elements and products of their disintegration. Radioactive disintegration begins in igneous rocks from the moment of their crystallisation from melting of magma and proceeds with constant speed until all reserves radioactive of elements will not be exhausted.

Therefore, having defined the maintenance in rock of this or that radioactive element and products of its disintegration and, knowing rate of decay, it is possible precisely enough (with possibility of an error about 5 %) to calculate absolute age of the given soil. For sedimentary soils it is necessary to accept approximate age in relation to absolute age of layers of effusive rocks. Long and laborious analysis of relative and absolute age of rocks in different regions of the globe, demanded hard work of several generations of geologists and paleontologists, has allowed to plan the basic marks of geologic history of the Earth. Boundaries between these divisions correspond a different sort to changes of geologic and biological (paleontologic) character. It can be mode changes sedimentation in the reservoirs, leading to formation of other phylums of sedimentary soils, intensifying of volcanism and orogenic processes, sea encroachment (sea transgression) thanks to lowering of considerable fields of a continental cortex or increase of level of ocean, essential changes of a fauna and flora. As similar events descended in history of the Earth irregularly, duration of various epoch, the seasons and aeons is various. Attracts attention huge duration of the most ancient geologic aeons (archeozoic and Proterozoic) which besides are not divided into smaller time interspaces (anyway, there is no still a standard division). It is caused first of all by a time factor - an antiquity of depositions archeozoic and a Proterozoic, undergone for the long history to a considerable metamorphism and the destruction which has erased marks existing once of development of the Earth and life. Depositions Archaean and Proterozoic aeons contain very few fossils of organisms; to this sign archeozoic and a Proterozoic unite under the name “cryptozoic” (a stage of the latent life) opposing to affiliation of three of the subsequent aeons - "phanerozoic" (a stage of obvious, observable life). The age of the Earth is defined by various scientists to a miscellaneous, but it is possible to specify in the approached figure 5 of billion years.

Life development in a cryptozoic.

The age, concerning a cryptozoic, - archeozoic and Proterozoic - together proceeded more than 3,4 billion years; thus the cryptozoic compounds not less than 7/8 all geologic history. However in cryptozoic depositions very few fossils of organisms, therefore representations of scientists about the first stages of development of life during these huge time intervals substantially hypothetically have remained.

Cryptozoic depositions

The most ancient residual of organisms has been found in the sedimentary stratas Rhodesia having age of 2,9-3,2 billion of years. There traces of ability to live of seaweed (possibly, blue-green) are discovered, that convincingly testifies, that about 3 billion years ago on the Earth already there were photosynthesizing organisms - seaweed. Obviously, life appearance on the Earth should descend much earlier, maybe, 4 billion years ago. The Proterozoic flora (filamentous forms in length to several hundreds micrometers and thickness 0,6-16 microns having a various constitution, monocelled microorganisms, for diameter 1-16 microns, also a various constitution) which residual has been discovered in Canada in siliceous shales on northern coast of lake Top is Most known average. The age of these depositions compounds about 1,9 billion years.

In the sedimentary soils formed in a time interval between 2 and 1 billion years ago, often there are stromatolites that speaks about a wide circulation and awake photosynthesizing and a reef of building activity of blue-green seaweed in this season.

The following major boundary in life evolution is documented by a number of finds of fossils in the depositions having age of 0,9-1,3 billion of years among which the residual of unicells in the dimension 8-12 microns in which it was possible to distinguish the endocellular frame similar to a core are found fine safety; stages of division of one of kinds of these unicells, reminding stages of a mitosis - a method of division eucariotic are discovered also (i.e. Having a core) cages.

If interpretation of the described fossils is correct, it means, that about 1,6-1,35 billion years ago evolution of organisms has driven the major boundary - level of the organisation an eucaryote has been reached.

The first traces of ability to live of worm-shaped metazoans are known from serotinal Riphean depositions. During Sorbian time (650-570 million years ago) there were already various animals, possibly, belonging to various phylums. Not numerous impresses of malacoid Sorbian animals are known from different areas of globe. The rich serotinal Proterozoic fossil fauna discovered Sprigg in 1947 in the Central Australia is most known. Investigating this unique fauna Glaessner considers, that it includes about three ten kinds of very various metazoans concerning different phylums

The majority of forms belongs, possibly, to coelenterates. She is a jellyfish the similar organisms possibly "soaring" in a strata of water, and the polypoid forms attached to a sea-bottom, the solitary or colonial, reminding modern alcyonarias, or sea feathers. Remarkably, that all of them, as well as other animals Ediacaran fauna, are deprived a firm atomy.

Except coelenterates, in quartzites Pound containing Ediacaran fauna, remains of the worm-shaped animals ranked to flat and Annelidas are found. Some kinds of organisms are interpreted as possible ancestors of arthropods. At last, there is variety of fossils of an unknown taxonomic accessory. It specifies in huge diffusion of a fauna of multicellular malacoid animals to Sorbian time,

As the Sorbian fauna is so various and includes the highly enough organised animals, it is obvious, that before its occurrence evolution proceeded already long enough. Possibly, metazoans have appeared much earlier - somewhere in an interspace 700-900 million years ago.

Sharp Augmentation of Oof of the Fossil Fauna

Boundary between Proterozoic and Paleozoic aeons (i.e. Between a cryptozoic and phanerozoic) it is marked by amazing change in structure and oof of a fossil fauna. Subitaneously (other word here, perhaps, also you will not select) after the stratas of the top Proterozoic almost deprived of traces of life, in sedimentary soils of Cambrian period (the first season of a Paleozoic age), since the lowermost horizons, there is a huge diversity and an abundance of the residual of fossil organisms. Among them the residual of sponges, brachiopods, molluscums, representatives of died out phylum Archaeocyathi, arthropods and other bunches. By the Cambrian period end there are almost all known phylums of metazoans. This subitaneous “explosion the formation form” on Proterozoic and Paleozoic boundary - one of the most mysterious which till now completely have been not solved, events in life history on the Earth. Thanks to it the Cambrian beginning is so appreciable mark, that all previous time in geologic history is frequent (i.e. All cryptozoic) call a Pre-Cambrian.

Possibly, isolation of all basic phylums of animals has descended in the top Proterozoic, in a time interval 600-800 million years ago. Primitive representatives of all bunches of metazoans were the small organisms deprived of an atomy. Proceeding accumulation of oxygen in atmosphere and augmentation of power of the ozone screen by the Proterozoic end have allowed animals as it is specified above, to increase the dimensions of a body and to get an atomy. Organisms had an opportunity widely to be settled on small depths of various reservoirs that has led to substantial increase of a diversity of forms of life.