Kingdom Monera was the oldest kingdom of living organisms. The organisms in the kingdom were simple, single celled and their cellular organelles were not covered by membranes. Prokaryotic bacteria were the first known Monerans. However, scientists think that Monerans were evolved into more complex eukaryotic organisms (Protists) with the passage of time.
But how did Monera (Prokaryotes) was evolved into Protista (Eukaryotes)?
Protista are eukaryotes, unicellular or simple multicellular organisms.Many theories were proposed for this evolution, but one that makes most sense was endosymbiotic theory. According to this, the first eukaryotic cells were evolved when two prokaryotic cells existed in an endo-symbiotic relationship. Larger prokaryotic cells engulfed smaller prokaryotic cells. The smaller cells got shelter and nutrients from larger cells and both co-existed in a mutualistic relationship. Both cells eventually evolved into organelles and got never aparted. This is how more complex organisms’ protists were evolved from simple monerans. It was a gradual process and took millions of years.
The earliest fungi were single-celled organisms that contain a flagella to move from one place to another. Recent studies indicate that fungi belong to a group of organisms which were evolved from protists over the course of time. These studies are based on the nucleotide sequence of fungi that matches to a large extent with old protists. It is estimates that fungi evolved 600 million years or even before.
