Final answer:
Modern DNA-based life may have arisen from an earlier RNA world, with RNA fulfilling the dual role of storing genetic information and catalyzing cell reactions before DNA and proteins evolved. The concept of a common ancestor is supported by genetics and the tree of life that shows the relatedness of all present organisms. This evolutionary trajectory began with simple, non-nucleated cells and eventually led to the diversity of life forms through processes like sexual reproduction.
Step-by-step explanation:
According to modern biological evidence, modern DNA-based life may have arisen from an earlier RNA world. This concept suggests that earlier life forms used RNA both to store genetic information and to catalyze chemical reactions within the cell, due to RNA’s ability to act like both DNA and proteins in present-day cells. Eventually, DNA and proteins evolved to take over these roles because of their greater stability and efficiency, leading to the complex life forms we see today. Moreover, the transition from an RNA world to a DNA world is significant because all cellular life now stores information in DNA, indicative of a common ancestor. The study of ancient rocks, genetics, and genomics provides valuable insight into this evolutionary process, although many details remain to be worked out.
Research in genetics and genomics has allowed for the construction of the "tree of life", showing that all life on Earth shares a common ancestor. Biochemical similarities and genetic evidence point to the three major domains of life - Bacteria, Archaea, and Eukaryotes - evolving from simpler forms that lacked nuclei. Over time, nucleated cells emerged, and life began to diversify remarkably, especially with the advent of sexual reproduction about 1.5 billion years ago. The rich tapestry of life we observe today is a product of billions of years of evolution, beginning from simple molecules to the diverse and complex organisms that populate the Earth now.