Biological classification is the process by which scientists group living organisms. Organisms are classified based on how similar they are. Historically, similarity was determined by examining the physical characteristics of an organism but modern classification uses a variety of techniques including genetic analysis. Simple differences in the morphological characteristics initially led to the classification of plant and animal species, which further paved the way for classification that was backed by definite scientific research and study. The main criteria for the five-kingdom classification were body organisation, cell structure, mode of nutrition, reproduction, phylogenetic relationships. In this kingdom of classification, bacteria were included in the Kingdom Monera while bacteria are cosmopolitan in the distribution.
These entities exhibit tremendous metabolic diversity. Where entities belonging to Kingdom Protista include single-celled eukaryotes, species of Kingdom Fungi exhibit great diversity in their habitat and structure. Kingdom Plantae compromises of all eukaryotic chlorophyll-containing entities while Kingdom Animalia includes heterotrophic eukaryotic, multicellular entities that lack a cell wall.