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

Scientists believe that prokaryotes existed earlier than eukaryotes because certain eukaryote cell structures resemble prokaryotes.

Explanation:

Prokaryotes are simple organisms as compared to eukaryotes. The scientific evidence proved that simple prokaryotic organisms were engulfed by larger prokaryotic organisms to give rise to eukaryotes. For example, the chloroplast and mitochondria once occurred as simple prokaryotic organisms which were engulfed by the larger prokaryotes.

Evidences also prove that prokaryotes were the organisms that formed life on earth as they could survive the harsh conditions of the earth at that time. Hence, all these points proved that prokaryotes existed earlier than 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.

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