According to the endosymbiosis theory scientist believe early eukaryotes form from prokaryotes why do scientist believe that prokaryotes existed earlier eukaryotes

Endosymbiosis of prokaryotes resulted in the formation of eukaryotic organelles and this has made scientists believe that prokaryotes existed earlier than eukaryotes.

Explanation:

Eukaryotic organisms have increased complexity and advanced development than prokaryotic organisms. Studies have revealed that the whole development of eukaryotes was from the prokaryotes. Eukaryotic cells have a true nucleus and well formed cell organelles unlike prokaryotes.

Mitochondria is the energy factory of eukaryotic cells which is absent in prokaryotic cells. Studies have predicted that mitochondria was formed from a prokaryotic bacterium engulfed by a cell. The engulfed bacterium became a permanent resident of the cell and supplied chemical energy to it.

In return it received protection and nutrients from the host cell. Thus there came up an internal symbiosis and finally they evolved into a single lineage forming the cell organelle mitochondria. This is an example of endosymbiosis.