How many kingdoms are recognized in biological classification?

In biological classification, five kingdoms are commonly recognized in traditional taxonomy. These kingdoms are Monera (which includes prokaryotic organisms like bacteria), Protista (which includes diverse eukaryotic microorganisms), Fungi (organisms that absorb nutrients through decomposition), Plantae (the plant kingdom), and Animalia (the kingdom of animals). This classification system was developed to reflect the fundamental differences in cellular organization and metabolic processes among different groups of organisms.

The idea of five kingdoms was largely popularized by the work of scientists like Robert Whittaker in the 1960s. He established criteria for distinguishing among these kingdoms based on factors like cellular organization (whether an organism is prokaryotic or eukaryotic), the mode of nutrition (autotrophic versus heterotrophic), and reproductive strategies.

While there are modern systems of classification, such as the three-domain system proposed by Carl Woese that divides life into Archaea, Bacteria, and Eukarya, the traditional five-kingdom classification is still widely taught and used as a foundation for understanding the diversity of life on Earth.