The oldest known rocks are about 3.8 billion (3800 million) years old.It corresponds to 38, 000, 000 centuries. According to Geologists and Geophysicists our planet earth is 4.7 billion (4,700 million) years old.
In this ancient time scale evidenes showed that the first life originated 2.5 billion (2,500 million) years ago. Hence from the formative stage for nearly 2,200 billion years there was no life on earth. Such a period in earth’s history is known as the Azoic era (2,200 to 5,000 billion years ago). Evidences show that during this era the earth was a hot sphere.Gradually the upper surface of the earth cooled down. It resulted in solidification and formation of rocks and rocky terrain. Further water molecules were formed resulting in accumulation of water and water reservoirs as wate masses and land surface were established. These transformations provided a suitable condition for the origin of the first life.
Once the life originated and established, evolutionary changes tookplace. Changes happened in the structure, organisation and living methods of,organisms, depending on natural surroundings and changes in natural surroundings.Thus fauna and flora started flourishing on earth. The water masses
were fully exploited. Later land surfaces were invaded by plants and animals.The Geological time succeeding Azoic Era, was dramatic and rich is life. This period is divided into three eras. These were significant periods in earth’s history. Of these, the oldest era was the Paleozoic era. It ranged from 600 to 210 million years ago. Thus its duration was nearly 390 million years. This era saw the origin and adaptive radiation of sponges, starfishes snails, insects, crabs, and terrestialised amphibians and reptiles.
The Paleozoic era was followed by middle period named as Mesozoic era. This era ranged from 65 to 210 million years ago. Its duration was145 million years. During this era, among animals the reptiles came to prominence. Hence this era is known as the golden age of reptiles. Further this era saw the origin and development of birds and reptiles. The period ranging from 65 million years till date is named as the
Coenozoic era. This era is characterised by rapid evolutionary changes in mammals. This era is known as the Age of mammals. Geological time scale A geological calendar has been formulated by assessing the age of
rocks and rock sediments. Based on age, and events, the ancient period from earth’s history is formulated into eras-periods-epochs. Each division in the geological calender is clearly identified and demarcated. Incidents pertaining to earth surface, plant and animals life are neatly recorded. The influence of
geological and climatic changes on the life and the evolution of the living organism had been well analysed.
In this ancient time scale evidenes showed that the first life originated 2.5 billion (2,500 million) years ago. Hence from the formative stage for nearly 2,200 billion years there was no life on earth. Such a period in earth’s history is known as the Azoic era (2,200 to 5,000 billion years ago). Evidences show that during this era the earth was a hot sphere.Gradually the upper surface of the earth cooled down. It resulted in solidification and formation of rocks and rocky terrain. Further water molecules were formed resulting in accumulation of water and water reservoirs as wate masses and land surface were established. These transformations provided a suitable condition for the origin of the first life.
Once the life originated and established, evolutionary changes tookplace. Changes happened in the structure, organisation and living methods of,organisms, depending on natural surroundings and changes in natural surroundings.Thus fauna and flora started flourishing on earth. The water masses
were fully exploited. Later land surfaces were invaded by plants and animals.The Geological time succeeding Azoic Era, was dramatic and rich is life. This period is divided into three eras. These were significant periods in earth’s history. Of these, the oldest era was the Paleozoic era. It ranged from 600 to 210 million years ago. Thus its duration was nearly 390 million years. This era saw the origin and adaptive radiation of sponges, starfishes snails, insects, crabs, and terrestialised amphibians and reptiles.
The Paleozoic era was followed by middle period named as Mesozoic era. This era ranged from 65 to 210 million years ago. Its duration was145 million years. During this era, among animals the reptiles came to prominence. Hence this era is known as the golden age of reptiles. Further this era saw the origin and development of birds and reptiles. The period ranging from 65 million years till date is named as the
Coenozoic era. This era is characterised by rapid evolutionary changes in mammals. This era is known as the Age of mammals. Geological time scale A geological calendar has been formulated by assessing the age of
rocks and rock sediments. Based on age, and events, the ancient period from earth’s history is formulated into eras-periods-epochs. Each division in the geological calender is clearly identified and demarcated. Incidents pertaining to earth surface, plant and animals life are neatly recorded. The influence of
geological and climatic changes on the life and the evolution of the living organism had been well analysed.
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