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The evolution of life

The Evolution of Life: The Paleozoic Era
The Paleozoic Era covers the duration from 5 hundred million, 43 million years to 2 hundred billion, 46 million years ago and including the trilobite, showed an explosive increase in invertebrates. This period is divided into the Cambrian period, the Ordovician period, the Silurian period, the Devonian period, the Carboniferous period and the Permian period and can be grouped as the First Term Paleozoic Era (Cambrian-Ordovician), Middle Paleozoic Era (Silurian-Devonian) and the Later Paleozoic Era (Carboniferous-Permian). Today’s scientists decided that the trace fossil named Trichophycus pedum was from the Cambrian period. During the Proterozoic Era the cruel coldness passed by the warmth followed with the Cambrian period. Life with firm shells and bone structure made explosive appearances and rapidly developed. The trilobites are the most representative living organism for this period and after that Brachiopoda type were abundant. With the exception of vertebrae most other animals rapidly appeared which resulted in this being called the Cambrian explosion.

The Ordovician Period covers the period 4 hundred million 90 million years to 4 hundred million 43 million years ago. In the early stages the climate was very warm and coral reef formed abundantly near equator districts. Nearing the latter period the Gondwana continental started moving towards the south. Due to this a massive glacier formed and the sea level descended which became the reason for mass extinction. Ordovician living organisms are not great difference from those of the Cambrian period. Trilobites, brachiopoda, original fish type, cephalopoda, gastropoda, coral and sea lilies were abundant. Also, primitive land plants also appeared but they are a sign of the discovery of new habitat for the life which was limited to the sea.

The Silurian Period (4 hundred million 43 million years-4 hundred million 17 million years ago) was a period when the Earth was undergoing some drastic changes. Earth’s climate became comparatively stable and with the melting of the massive glacier the sea level became to rise. Coral, sea lilies and brachiopoda were abundant. The eurypterus, which appeared in the Ordovician period was also greatly abundant but became extinct in the Devonian period. The jawless fish was distributed in wide regions, and fish with jaws and freshwater fish appeared. Following the appearance of vascular plants on land ants and such arthropoda appeared widely.

The Devonian period was the period which could be called the period of fish as fish were in such abundance. At the time brachiopoda, sea lilies, echinoderm, heliophyllum and coral were abundant. In the early stages the largest plant was 1m but later became a forest. At the end of the Devonian period pteridophyta, horsetail plants and seed plants make an appearance. The examination of heliophyllium fossils showed that the Devonian day compared to the present day was 22 hours long and there were approximately 400 days in the year. Tetrapods and arthropods made an appearance for the first time. Towards the end of the period following the end of the Ordovician period mass extinction occurred.

The Carboniferous period covered the duration from 3 hundred million 54 million years to 2 hundred million 90 million years ago. The word carboniferous refers to the geological stratum of England being abundant production of coal at the time. Coal sediments were discovered by the whole world equally nut the coal in the geological stratum of America had a different condition. The upper stratum encompassed briquette but the lower stratum was almost made up of limestone. Therefore it was decided the lower part which was formed of limestone and the upper part which was formed of briquette would be divided and used accordingly into Mississippian and Pennsylvanian.

The largest evolutionary incident in the Carboniferous period was the appearance of the amniote egg. In addition, winged insects made and appearance and became abundant and large sized insects also appeared. Trees became exuberant and formed large forests and due to this the density of oxygen became higher.

The Permian period covers from 2 hundred million 90 million to 2 hundred 48 million years ago and was the last period of the Paleozoic Era. At that time the Pangaea which was the first continent was formed. The Pangaea was surrounded by the massive Panthalassa from the east side to the Tethys Sea. This period saw an extermination of a lot of living organisms and the middle period organisms started developing. A lot of organisms including the trilobites and the heliophyllum diminished during this time.

Mesozoic Era
This covers the period about 46 hundred million years ago, in the center of the geological age, and covered a period approximately from 2 hundred million 50 million years to 65 million years ago. Due to the mass extinction which occurred during the Permian period led to the extinction of both sea and land creatures and after this extinction a new evaporation appeared on this emptied surface. The extinction of the dinocephalia was followed by this and the remaining cynodonts and dicynodonts filled up another part. The archosaurian, which were the most representative, only appeared after thousands of millions of years after the middle Mezozoic era became extinct towards the end of the Permian period. Here the ichthyosaurs, elasmosaurus, mosasaurs and also reptiles, dinosaurs and pterosauria.

Due to P/T mass extinction the damage of mollusca and echinodermata as well as to plants. Each taxon had one or even two forms of life groups disappear and the ones which had been maintained in the Paleozoic Era were hard to recover in the Triassic and Jurassic periods. The latter half of the Mesozoic Era saw the Jurassic period and the early Cretaceous period and the raising of the sea level occurred. An equal climate around the world led to creative evolution being newly born. These kinds of climatic changes led to an affect of diffusion. As a well known example birds, mammalia incorporating placenta, angiosperm plant can be mentioned. The angiosperms were predominant in most regions towards the end of the Cretaceous period. However partially after K/T mass extinction research results found that cycad and ferns were still abundant. In the sea also fundamental changes occurred and this was mollusca called the rudist and new forms of shark planktonic foraminifer and birds started appearing.

In the Aptian-Albian period the sea level height and high water temperatures were all at the highest peak and in line with this the climatic impoverishment of the environment could be caused. If characteristics of the later Cretaceous period were looked at then it is visible that with all forms of life small forms of evolution took place. This is due to the fact that in the early Mesozoic Era characteristics of a large body were inefficient in the variable environment. We can find examples with today’s lizards, snakes and the predecessor of mammalia. At the end of the Mesozoic Era, saurosuchus became extinct and birds and mammalia still exist today.

Cenozoic Era
From 65 million years ago the Cenozoic Era started and is called the mammalian period. In this period invertebrates, fish, reptilian and such living organisms were already possessing modern appearances but mammalian, birds, protozoa and angiosperm were still newly appearing or evolving.

For the duration of paleogene the climate worldwide was similar to the Mesozoic Era and tropical climates occurred. In neogene period the Himalayan orogeny occurred and due to the protrusion a chilly climate settled in all around the world. During the paleogene(paleogene) due to the glacial age a constant chilly climate was maintained and during the interglacial period a warm climate remained.

Towards the end of the Cretaceous period mass extinction and the shallow sea and the ocean ammonites, belemnites and teleost fish and such mostly became extinct. In the sea planktons existed abundantly and planktons, crustacean, mollusca, polychaete and insects were occupying. Whales and eocene epoch appeared for the first time and the large sea reptilia which were abundant during the Mesozoic Era became substituted by ground. At the end of the Certaceous period the protostegid- archelon and similar large turtles became extinct and the sea turtle which is still living today remain in existence.

In the Paleocene Epoch a lot of mammolia and birds became abundant in the warm tropical climates. For the duration of the early neogene period the shallow sea caused rupture in the land and individually different mammalian incorporating different systems evolved. The crocodile-formed champsosaurs remained even during the K-T mass extinction and remained in existence even until the Cenozoic Era but met with extinction in the paleogene period. The very first whales to have teeth in the sea started appearing. The foraminifera, belonging to the sea protozoa were mostly microorganisms but during the Eocene epoch appeared in a form larger than a coin and took on appearances similar to today’s echinoderms, corals, bryozoan and sponge. The insects on land mostly took on appearances of today.

From the start of neogene the grass which had successfully evolved initiated animal evolution. These changes led to an enormous grass field and long-legged animals, which were suited to such an environment, started appearing. The equiidae was the most successful living organism to evolve during neogene. Equiidae as well as other herbivore animals formed appropriate teeth which enabled them to feed on stiff grass which put them in a superior position to other animals. Mastodons existed in every land except Australia. In addition, the ground passage in South America meant that other living organisms started flowing in from the north. Prior to this many mammalia which could be differentiated from other areas were living. In the sea whales which had a similar form to mammals today appeared and replaced the whales with teeth which had appeared in the beginning. In addition carnivorous shark exist until today without major changes.

During the paleogene(paleogene) period today’s vegetation and appearance of invertebrates can be confirmed. However, during the Cenozoic Era the mammalian which were in abundance became extinct in this period and cannot be found or seen today. In particular various forms of woolly mammoth and woolly rhinos became extinct. Humans gradually started to evolutionalise from the glacial age in Europe. Due to the excessive hunting activities of humans and the change in climate the extinction of aschelminthes also occurred.

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