The scientists have used the common historical and functional basis of living organisms to create the geological time period.
<u>Explanation:</u>
All the living things present on earth have gone through the evolutionary process. According to the researches, the oldest fossil found on the earth can be traced 3.5 to 3.7 billion years back, and life today on earth has been evolved from a common ancestor through natural selection or adaptions.
The geological time period shows all the changes in living organisms in different eras eons, eras, periods, epochs.
The geological time scale is a record and division of everything that has happened on Earth. This is not an absolute scale as we have an incomplete fossil record.
The geological column was created by placing Earth's rocks in order of their relative age. The scale was obtained by dividing the geological column into different time periods through studying large scale changes in the fossil record. This was further tuned with the help of radioactive dating.
Thus the divisions of the geological time are determined by the observed major changes in the Earth's life forms. It is dependent on the history of life on Earth.
