Fossil evidence indicates that the first cell existed 3.5 billion years ago. Many suggestions have been made about the first ever cell, one of which was suggested that the first ever cell was prokaryote beacuse they did not require oxygen to survive, this idea lead to the assumptions that life began in the ocean. 

 

Research has stated that 2.5 billion years ago prokaryotes that were able to photosynthesise became prominent. These prominent cells were similar to what is known today as blue-green algae or cyanobacteria of today. Due to oxygen being a by-product of photosynthesises, when the changes of the photosynthetic bacteria’s began to drastically evolve the composition of the atmosphere was compromised with the increase of concentrated oxygen. This process then allowed cells to use oxygen as part of their metabolism, thus becoming more complex. This step became a crucial phase in the evolution of life on earth.

 

When compared to eukaryotic cells, prokaryotic cells are much simpler in their structure and metabolism. However Eukaryotic cells would not have been able to survive the harsh conditions provided by the early stages of earth’s atmosphere.   This knowledge then led to the conclusion that the first prokaryotic cell existed long before the first eukaryotic cell. Fossil evidence has shown that the existence of Prokaryotic cells have said to be around for at least 3.5 billion years were as the first eukaryotic cell has thought to have been around for only 1.5 billion years.