What is the three kingdom classification system?

Answer: Ernst Haeckel classified the three kingdoms in his work. The three kingdoms’ main subgroups are Plantae, Protista, and Animalia.

• Eukaryotic and autotrophic organisms make up the plantae.
• Eukaryotic, heterotrophic, and autotrophic organisms are all included in the class of protozoa.
• Eukaryotic and heterotrophic organisms are found in Animalia.