All life story of Earth is divided into long pieces which it is accepted to call eram. Everyone is distinguished by certain changes in geography and climate and also considerable development in a plant and animal life.
Archaean era
This era originates from the moment of formation of Earth as planets, and about 1 billion years lasts. During this period there were first inhabitants of our planet – anaerobic bacteria. Then there was a photosynthesis – the most important stage of evolution of life which caused division of the organic world into vegetable and animal. At the end of this period there were a mnogokletochnost and sexual process which raised a possibility of adaptation to environmental conditions.
Blue-green seaweed and doyaderny cyanobacteria were the first photosynthesizing organisms.
Proterozoic era
The stage of development of Earth, huge on duration, lasting about 2 billion years. During it on our planet there were first simplest organisms. During this period of a bacterium and an alga reach the dawn, the largest deposits of iron ores of organic origin are formed. Living organisms become multicellular (arkheotsiata, sponges), they form bodies. They change a form and players of earth crust, form the biosphere and promote accumulation of oxygen in the atmosphere. At the end of the Proterozoic era, Annelidas appear. All vital processes of this period proceed in the ocean.
Palaeozoic Era
This piece is presented by 6 periods: Cambridge, ordovician, Silurian, Devonian, coal and Perm. In fauna different types of fishes, including sharks appear and develop, appear, and then corals die out. There comes the age of Amphibia a bit later – grasshoppers, bugs, reptiles. Flora of this era is presented by development of the dense woods along coast of the rivers consisting of tree ferns and the first coniferous trees. The geography and climate of this period constantly change. Freezing at the end of the Ordovician Period is replaced by warming and mild climate. In the Devonian Period the downpours alternate with the drought, in coal there occurs freezing which then is replaced by warming, a heat and an arid climate. Such variety of climatic conditions is explained by continuous change of position of continents and the greatest cataclysms.
As a result of it there are various mountain tops including the Ural ridge and the Himalayas.
Mesozoic Era
The Mesozoic Era is presented Triassic, Jurassic and cretaceous by the periods. In fauna the dinosaurs and various reptiles become the dominating group, frogs, sea and overland turtles, new species of shrimps and corals appear. There are predecessors of modern insects and birds a bit later. At the end of the era there is an extinction of dinosaurs and pterosaurs. The climate becomes softer and all land overgrows various vegetation: predecessors of modern pines and cypresses, the first flowering plants. The interrelation between plants and insects gets better. In the Mesozoic Era there is a split of continents and removal them from each other, islands are formed. The Atlantic Ocean is formed and extends, the sea floods huge land areas.
Cenozoic Era
Modern era which began 66 million years ago. During this period angiospermous plants, birds, mammals and the person appear. In the middle of the era there are already main groups of representatives of kingdoms of wildlife. Bushes and herbs develop, there are meadows and steppes. The main types of biogeocenoses in the nature and an agrocnosis are formed. There is use of the nature by the person for satisfaction of his requirements. As a result of influence of the person the organic world and the nature changes.