How to Classify Organisms by Kingdoms

Examine or research the organism to determine how it gets food. If the creature makes its own food using energy from the sun (or undersea thermal vents), it is an autotroph. If the creature instead eats something, it is a heterotroph. Look at the creature under a microscope and check for round, green structures called chloroplasts within its cells. The presence of chloroplasts makes the creature autotrophic. The lack of chloroplasts indicates a heterotroph.

Determine the number of cells comprising the creature. If something is visible to the naked eye, it is multicellular. For smaller creatures, microscopic examination is necessary. Look at the creature and count the number of individual cells. Creatures with more than one cell are multicellular. Single-celled creatures are unicellular.

Examine the creature's cellular structure under a microscope. Every cell on Earth is either prokaryotic or eukaryotic. Prokaryotic cells are the smallest, simplest cells. They lack a nucleus and other major cell parts, living with rudimentary genetic material and cellular tools. Only the highest magnification levels on a microscope show prokaryotic life. Eukaryotic cells are significantly larger and more complex. These cells contain a nucleus, mitochondria and other large cell parts. Standard and low magnification levels easily show eukaryotic life.

Look for a cell wall or cell membrane. Under the microscope, a cell wall seems rigid and geometric. A cell wall adds a definite shape to every cell, allowing for little flexibility or plasticity. A cell membrane provides much less strength but lets a cell change shape drastically as conditions merit.

Combine the results from cell type, cell number and food source. Each Kingdom has a different combination of results. Kingdom Animalia's creatures are heterotrophic, multicellular eukaryotes with a cell membrane. Kingdom Fungi's creatures are heterotrophic, multicellular or unicellular eukaryotes with a cell wall. Kingdom Plantae's species are autotrophic, multicellular eukaryotes with a cell wall. Kingdom Protista's characteristics are autotrophic or heterotrophic, unicellular eukaryotes with either a cell wall or a cell membrane. Species in Kingdom Eubacteria are heterotrophic, unicellular prokaryotes with a cell wall. Species in Kingdom Archaebacteria are autotrophic, unicellular prokaryotes with a cell wall, but these species derive their energy through unconventional methods such as living by hydrothermal vents. Most live in extreme environments similar to those found on Earth billions of years ago. They do not use or need the sun.