These worksheets look at scientific taxonomy and the classification of organisms.

This series of worksheets start out by explaining the difference between taxonomy and classification. As students begin to learn the complexities that are examined by a taxonomic structure, we start to have them explore this in detail. Students will begin naming all types of different creatures. We will finish off by spending some time with the single celled protist which are representatives of simple alga. We have several sheets that help students begin to understand how organisms are grouped and sorted.

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Taxonomy and Classification Worksheet

Taxonomy and Classification

Number the seven major taxonomic groups in order from the one containing the largest number of types of organisms to the one that containing only one. This worksheet has students look at all the characteristics exhibited by members of each Kingdom.

Classification of Animals and Microbes Worksheet

Classification of Animals and Microbes

Fifteen different organisms are shown below. For each, provide the common name and the name of the phylum to which it belongs.

Classification of Protists Worksheet

Classification of Protists

See what you know your single celled pals. Match the description or definition in the left column with the correct word in the right column. Note that not all words in the right column are used.

Protists Classification Worksheet

Protists Classification

Circle the choice of the correct answer. We see what makes these things tick

Why Do We Classify Organisms?

The world consists of trillions of living organisms- possibly even hundreds of trillions. In fact, one estimate holds that there are about 8.7 million species of living organisms in the world. When we talk about species, it is one of the many ways we classify organisms-but why is this classification necessary?

We classify organisms because it makes studying them much more manageable. It also makes talking about these organisms easier, as we can better communicate that we are talking about a group of organisms rather than an individual organism. 

Carolus Linnaeus (a Swedish Scientist) recognized early that we needed to clearly be able to communicate to each the exact organism we were discussing. Not all dogs are the same, just like elephants. Linnaeus created a set of rules for naming system for organisms from bacteria to the blue whale. Linnaeus chose to use Latin words to define names in the scientific system. He found that each organism could be clearly defined in a naming system consisting of seven levels. The naming system starts as general as naming a Kingdom of each organism which defines if the organism is an animal, plant, protest, fungi, bacteria, or prokaryote. When students first start to work the various levels of animal and plant classification, they often do not see the point in it. Classification is very important because it ensures that scientists are studying the correct organism. There are thought to be just under nine million different species on Earth, it is proper scientific procedure to make certain you catalog which species you are studying.

Reasons We Classify Organisms

There is such a vast array of organisms on the planet that it's simply impossible to study each individually—even if every human engaged in the pursuit. 

Classification Makes Researching Organisms Easier

Classifying organisms according to shared characteristics makes researching them easier- we can study a few specimens from a particular species, for example, and then extrapolate that our findings will hold for the rest of the species. 

For example, consider dogs (or the species Canis familiaris). There are approximately 900 million dogs worldwide, so checking every dog in the world to see if they have four legs is implausible. However, it is possible to extrapolate that (barring injury or illness) they will all have four legs because other examples of their species do so. 

This example is relatively simple-though you can extend the model to more complex types of research. For instance, we can extrapolate that organ transfer is possible for all healthy humans without testing it on all healthy humans because it has worked in the past. Researchers also use this concept when researching medications and the properties of a particular organism. 

Classification Makes Talking About Organisms Easier

Aside from making it easier to study living organisms, we classify organisms because it makes talking about them more manageable. For example, consider a situation where two cats of different colors are in front of you. 

“Cat” is a classification. Because this classification exists, you can distinguish between the two easily by saying “black cat” and “white cat.” If these classifications did not exist, communicating would be made more complex. 

It would be even more challenging if the cat were not in front of you-you would have to describe what a cat looks like, saying, “a creature that walks on four legs and meows.” As you can see, one could easily misunderstand this description-it applies to both domestic cats and larger feline predators like snow leopards and cheetahs

When you can classify a cat as a cat—or even an animal as an animal-it makes it much easier to talk about them to another person.

How We Classify Organisms

Taxonomists classify organisms according to the following format:

  • Domain: The highest order of classification. There are three domains—bacteria, archaea, and eukarya.
  • Kingdom: There are generally five or six accepted kingdoms—Animalia, Plantae, monera, fungi, Protista, and (occasionally) archaea. 
  • Phylum: This classification separates organisms in a kingdom based on how closely they are related evolutionarily and what similar features they share.
  • Class: Organisms of the same class share physical similarities, which are more pronounced within the category than within the Phylum.
  • Order: Like class, taxonomists differentiate organisms from the same class into orders depending on physical similarities. For example, Artiodactyla is an order of the class Mammalia where all members have cloven hoofs and even-numbered toes.
  • Family: Again, classification into families depends on shared physical similarities between members of an order. For example, Canidae is a family where all members have the same basic physical form and walk on their toes.
  • Genus: Members of a Genus are very closely related and share numerous physical similarities. For example, the members of the genus Panthera include lions and tigers. These animals are visibly more similar to bobcats, despite all three being members of the Family Felidae.
  • Species: The most fundamental unit of classification; all species members are capable of breeding with each other and producing fertile offspring. This reproductive consideration is why lions and tigers are not the same species—while they can reproduce, they do not produce fertile offspring. However, different dog breeds can breed with each and produce fertile offspring, because all dogs share the same species.

Final Thoughts

We classify organisms because it makes research significantly easier. Additionally, it makes it much easier to communicate what you’re talking about with other researchers and other people in general.