6 The 5 Kingdoms of LIFE

There are millions of living organisms on Earth... and humans, in their sense of wonder, have tried for centuries to see some order in the chaos of these multitudes.

The early Greeks tried to classify all inanimate objects as fire, air, earth, and water, and the Greek philosopher Aristotle further classified living things as either Plant or Animal. He grouped animals into Land Dwellers, Water Dwellers, and Air Dwellers. This didn't work very well, as this system grouped elephants and earthworms, whales and water striders, flies and falcons. These things aren't alike! The efforts to classify living things saw great progress in the work of Carl Linnaeus, whose book Systema Naturae ("The Natural Classification", based on his religious concept that you could understand God by studying nature, his creation), was published in 1735. Botanists later tried to classify living creatures by means of locomotion, grouping butterflies and bats (flying), barnacles and barley (both rooted in place). This system of classification didn't work out very well, either (bats and butterflies are pretty different, aren't they?), so other attempts were made. While some of his concepts have been significantly changed, we still keep much of his ideas (hierarchical classification and system of binomial nomenclature). Let's pretend we are young botanists like Carl Linneaus and see how we might classify living things that we know at Cazadero.

This system works well until... This process is called photosynthesis, and may be one of the most important chemical reactions on the face of the earth. plants animals The most obvious grouping is into two groups, plants and animals. This system works well until... This classification works rather well, and for many years we were all taught about the Plant Kingdom and the Animal Kingdom in school. Plants, such as redwood trees, are characterized not by the fact that they don't run around, but by the fact that they all make their own food out of sunshine, water, and carbon dioxide, by means of chlorophyll (the stuff that makes plants green). Animals, on the other hand, either eat plants (such as deer) or they eat other animals that do eat plants (such as mountain lions who eat the deer). This classification system works pretty well, and we still talk about deer as being members of the Animal Kingdom and redwood trees as being members of the Plant Kingdom.

This system works well until... ...until you try to classify a mushroom! Hmmm. Let's see. It's not green. Scientists tell us it that's because it does not contain chlorophyll. It doesn't make its own food, so it can't be a plant. We learned that all plants make their own food. But it doesn't eat, either: mushrooms don't have mouths! So we need to add the Fungi Kingdom to the Plant Kingdom and the Animal Kingdom. Now we have three kingdoms. So it can't be an animal, because we learned that all animals eat food. So how do mushrooms get their nourishment? Mushrooms are a type of fungus, and all fungi (the plural of "fungus") neither make food nor eat it: they absorb it. This system works well until... Almost all of the body of a mushroom is actually underground, made up of tiny little strings of cells called hyphae. They are so tiny that they are only 1/50th the diameter of a human hair! How's that for small? The hyphae grow out until they run into something that the fungus thinks is tasty, and the hyphae grow into the food (mostly dead plant and animal matter) and absorb its nutrients directly into its own cells.

This system works well until... ...until you try to classify bacteria! Actually, bacteria are found everywhere but you can't see them anywhere because they are so small. Millions of them are in a single drop of water. So we need to add the Monera Kingdom and now we have four kingdoms. Bacteria are very different from plants, animals, and fungi, and not just because of size. All of the other living things (plants, animals, fungi) are made up of thousands, or billions, or even eleventeen gazillions, of cells, and each of their cells has a nucleus (the scientists call this "eukaryotic"), a central command center that tells the cell what to do. Bacteria are always made up of just one cell, and their cell has no nucleus (the scientists call this "prokaryotic"). Bacteria are actually more different from plants and animals than a mouse is from an elephant! They really need to be in their very own kingdom, the Kingdom Monera ("monera" comes from the Greek word for "single", referring to the fact that these organisms are all single-celled.) This system works well until...  High-powered microscopic views of bacteria (artificially colored)

Where do you stick slime? ...until you try to classify slime! Paramecium, a protist that swims around in pond water Algae need their own kingdom, the Kingdom Prostista. This group is also the home of other organisms that don't fit into the other kingdoms, including single-celled organisms like paramecia and diatoms, and multi-cellular organisms like kelp (which are just giant algae). Where do you stick slime? (I mean, after you scrape it off the bottom of your shoe!) So we added the Protist Kingdom and now we have five kingdoms. Where on the tree of life do you place slime, or more properly called algae? It is not an animal, because it does not eat things. It is not a plant, either, because it does not develop as a seed or spore within the mother plant. It is not a fungus, because it is green, and has chlorophyll, and can make its own food. And it is not a bacteria, because is has a cell nucleus. What is it? This system works well until... Volvox, a single-celled algae from a pond So we need to add the Kingdom Prostista to Plant Kingdom, Animal Kingdom, Fungi Kingdom, and Kingdom Monera. This five kingdom classification of living organisms is a good scheme with which to look and and learn about the wonderful world we live in. Diatom, a single-celled protist that floats in water and comes in the most bizarre shapes

Archaebacteria and Eubacteria Scientists began to research the Monera (bacteria) Kingdom further. They discovered that there were two distinctly different kind of bacteria and so the Monera Kingdom was split into two separate kingdoms: Archaebacteria and Eubacteria Archaebacteria are those that live in extreme environments like the ocean floor, and even your intestines! Eubacteria have a different chemical makeup than archaebacteria and are often helpful, like those found in yogurt. So, there you have it. The six kingdoms of life. Let’s Review…

LIFE The 6 Kingdoms of Animals Plants Fungi Protists Archaebacteria Eubacteria

The Kingdoms of Life can be diagrammed, with their relationships to each other and to the presumed origin of life: