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Scientists believe that there are over 10 million different kinds of lifeforms, or species, on Earth. Imagine trying to study and understand the lives, patterns, behaviors and evolution of so many different kinds of organisms. In order to make their job easier, scientists classify living things into groups based on how they are the same and how they are different.

Scientists who classify living things are called taxonomists. It is their job to look at every kind of living thing and determine how they are similar and how they are different to other living things.

To help scientists keep this all straight, they start by classifying, or by placing lifeforms in groups called kingdoms. 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 five kingdoms that biologists have developed are the Monera Kingdom,the Protist Kingdom, the Fungi Kingdom, the Plant Kingdom, and the Animal Kingdom.

The next group that scientists have developed to further classify living things is the Phylum (plural: phyla). Lifeforms are grouped together based once again on how they are similar and how they are different. Let's look at a phyla found in the Animal Kingdom. Everything in the Animal Kingdom is similar to each other in important ways. Can you think of some ways that animals are similar to one another? How are they different?


One important way that animals are different is whether or not they have a backbone. Animals with a backbone belong to the Chordata Phylum. It is important for you to know that some members of this phylum do not have a backbone. However, they do have a strengthening rod similar to a backbone.

This would not be the first time that such a change has been made. The first classification system developed 2,500 years ago by a Greek philosopher named Aristotle included only two groups, Plants and Animals. He further placed animals into three groups, those that fly, those that walk, and those that swim.

The five kingdoms currently accepted by most (but not all) scientists are the Monera Kingdom, the Protist Kingdom, the Fungi Kingdom, the Plant Kingdom, and the Animal Kingdom.