Hi guys 👋 in this blog let's see what happened 550 years ago in the earth and the reason how the plants and animals that live in water are live soo long…
WHAT HAPPENED 550 MILLION YEARS AGO: 🤔
About 500 and 50 million years ago a lot of changes took place on the earth. At that time probably the whole of the earth warmed up. Result a lot of ice melted and the sea level rose. It is assumed that the composition of the seawater became calciferous, turning mollusks that lived earlier in the sea into animals with hard protective calcium shells or calcium skeletons. From the time onwards many animals started turning into fossils after death. The first such animal where the trilobites, and these wear later followed by the mussles and ammonities which or resulted to the octopus. 
CLASSIFICATION OF HISTORY OF THE EARTH: 
Like the history of human Civilization the history of the Earth too is divided into periods. However these periods cover not just a few centuries, but millions of years. Broadly we differentiate between the time preceding the period 550 million years ago and that time after that during with life developed very quickly on the earth researchers have gather the lot of data regarding the different periods of the earth history by studying fossils. Does became to know that at what time fishes and birds appeared on the earth why plants and animals lived in the sea for so long and what the different type of Dinosaurs ate.
WHY PLANTS AND ANIMALS LIV SOO LONG IN WATER:
The earliest plants and animals lived in the sea because conditions on the land where not favourable for life. Initially there was too little oxygen in the atmosphere forbrating moreover the Ozone layer of the atmosphere which prevents harmful UV radiation from the sun from reaching the ground had not yet formed. It was only after the drying of the shallow Seas that the first plans adapted to life outside the water they started doing photosynthesis and help increasing the oxygen content of the atmosphere and the forming the Ozone layer in the silurian period animals resemblings Scorpions inabitated the land. Insect and reptiles appeared in the devonian and Carboninferior periods. The growth of plants also increased during this period. 
DIFFERENT PERIODS IN THE EARTH'S HISTORY: 
After the 'Archeozoic' Period of the precambian which lasted till about 550 million years ago came the paleozoic era this year is subdivided into Cambrian, orodovician, silurian, devonian and there are many periods. 

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