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Kingdom Classification

A kingdom is the second largest kind of group used to classify organisms. They’re only smaller than domains, so kingdoms are still quite big. Yet, there’s six of them!  These kingdoms represent a very large group of lifeforms that are all similar in some ways, but can be very different from one another in other ways.  The process of placing organisms into these broad groups is called kingdom classification. Even today among scientists there is still much debate about how things should be divided.

Image of a butterfly on flowers.


Below is a video explaining the six different kingdoms and how they are split up:

Animalia – The Animal Kingdom

The animal kingdom is the youngest kingdom of living things. But, it’s also the largest. This makes Animalia exciting to study because it’s so diverse.

Still, to organize this kingdom, we have to ask what its members have in common. So, animals share these traits:

  1. Animals have flexible eukaryotic cells. This helps them move freely, unlike plants’ solid cells.
  1. Animals are multicellular. This allows some of them to be quite complex, like humans.
  1. Animals are heterotrophic. That means they eat for nutrients.

Kingdoms are very big groups. Yet, as you study animals, you’ll see that they all have these features. It’s amazing how life can be so diverse and similar at the same time!

Image of elephants in the animal kingdom.

Inspects, reptiles, mammals (like these elephants) are all part of the animal kingdom.

Plantae – The Plant Kingdom

Plants seem like they’d be easy to classify. They’re green and don’t move! Yet, organisms in the plant kingdom actually have very specific features. Although we can’t see all of them, they affect how plants live. Here are a few of these hidden features:

  1. Plant cell walls are solid. This makes plants rigid and unable to move very much.
  1. Plant cells contain structures called chloroplasts. This lets them do photosynthesis to make their own food.
  1. Plants are multicellular.

Of course, we can’t see all of these traits with our eyes. So, plants might be boring to us. But, imagine what your neighborhood would look like without plants! Even busy cities have gardens and flowers in store windows. Plants, while very ordinary, are an important part of our daily lives.

Image of a forest in the plant kingdom

A forest is a place full of plants. They’re all part of the same kingdom, the plant kingdom.


Organisms belonging to the Fungi kingdom are called just that: Fungi. To us, Fungi seem like strange organisms. They aren’t quite plants, and they sure don’t seem like animals. Yet, Fungi actually have features from both groups. These include:

  1. Fungi are eukaryotic organisms. They have the same type of cells as you and me!
  1. Fungi are heterotrophic. This is confusing because to us they don’t seem to eat. But, you have probably seen them do so. For example, when mold grows on food, the mold, a fungus, is eating the food!
  1. Fungal cells have cell walls like plants do.
Image of wild mushrooms in the fungi kingdom

These strange, orange organisms are mushrooms growing on a tree. Often, fungi, like mushrooms grow in forests.

Bacteria, Protozoans, and Archaea – Hidden Kingdoms

Now you might be wondering: where are the other kingdoms? Aren’t kingdoms supposed to be big? The word makes us imagine castles and high walls. Yet, there are actually tiny kingdoms all around you right now! The other three are just made up of microscopic organisms. This means you can’t see them with only your eyes. Although, if we only look with our eyes, we’ll miss a lot of unique organisms.

One of these kingdoms is called Bacteria. You’ve probably heard of bacteria. They’re those nasty things that give you the cold. As a result, we generally don’t like them. But, most bacteria won’t make you sick. Some of them are even helpful! Like organisms in any other kingdom, there are both good and bad Bacteria. We can’t assume without studying them.

Images of microbes in the monera kingdom.

Drawings of some microbes. We can’t directly see microbes, like Bacteria, Protozoans, and Archaeans.

Another of the hidden kingdoms is called Protozoa. Protozoans are a strange group of organisms. They are single-celled, like bacteria, but they behave and look like animal cells! More specifically, they are eukaryotic and eat for nutrition. Notably, Protozoans only live in moist environments.

Our last kingdom is called Archaea. Archaea is a special kingdom as it is also a domain. This is because archaeans are so different from all other living things! Yet, the differences between them and other microscopic organisms are complex. Of course, we can’t just compare them with our eyes. If you want to learn more about them, check out the resources listed below.

Other Great Resources:

Archaea, Protista, and Bacteria:

The Six Kingdoms:


Image of the five kingdoms - kingdom classification.

Written by:  Noah Louis-Ferdinand