The two kingdoms classification was suggested by Carolus Linnaeus in 1735. According to the classification, based on nutrition and locomotion, all living organisms were divided into two groups – Animals and Plants. The major problem of the classification is that prokaryotes (i.e., bacteria) are grouped with plants that are eukaryotic organisms. As a result, the two kingdom classification did not show any evolutionary relations between the two groups. In addition, the classification grouped unicellular and multicellular organisms, as well as heterotrophic fungi and autotrophic plants that are different in their structure and metabolism. Finally, some organisms (i.e., slime molds, lichens or unicellular organisms) did not fit any group as they possess features common for both groups.
According to five kingdoms classification, all organisms were divided into five groups: Monera (Prokaryotes), Protista, Fungi, Plantae, and Animal. The classification system separated unicellular protists from the animal group, as well as fungi and prokaryotes from plants. As a result, the animals and plants group became more homogenous. Next, isolation of prokaryotes is another advantage of the classification. Overall, the five kingdoms classification provided a better understanding of the evolutionary relationships between the organisms.