Kingdom is the highest rank, after the domain, which is normally used in the biological taxonomy of all organisms. Each kingdom is split into phyla.

There are 5 to 7 kingdoms in taxonomy. Every living thing comes under one of these kingdoms and some symbionts, such as lichen, come under two. There are at least:

• Prokaryotes or Monera – the most simple living things: bacteria and archaea
• Protista – eukaryotes that are not plants, fungi, or animals
• Fungi – mushrooms, moulds and other fungi
• Plantae – all plants, such as moss, trees and grass
• Animalia – all animals, including people. See List of animal phyla
• Chromalveolata – plastids containing chlorophyll.

The kingdom-level classification of life is still widely employed as a useful way of grouping organisms. Sometimes entries in the table, which are next to each other, do not match perfectly. For example, Haeckel placed the red algae (Haeckel's Florideae; modern Rhodophyta) and blue-green algae (Haeckel's Archephyta; modern Cyanobacteria) in his Plantae, but in modern classifications they are considered protists and bacteria respectively. However, despite these differences, the table gives a useful summary.

• There is no agreement at present on how many kingdoms there are in the Eukarya. In 2009, Andrew Roger and Alastair Simpson said this: "With the current pace of change in our understanding of the eukaryote tree of life, we should proceed with caution".^[17]

• Tree of Life