How Do We Name Organisms?

Biological classification represents how organisms are related with species being the most specific part. Biologists arrange organisms into a hierarchy of groups and subgroups based on similarities and differences, which have to do with how closely related they are.


Classification is a way of organizing anything into categories so that we can figure out how those things are similar to and different from each other. Any group of living or non-living things can be classified. For example, we can classify students according to many characteristics: their grade level, credits earned, whether they pick their nose, small school or age, among other things.

An amoeba. Her name might be Bobbi.

In the world outside of school, there are between 10 and 100 million different species of living things. Scientists have only named about 2 million of these species. Because we keep finding more species all of the time, we estimate that there must be many more species than already have been found! In fact, we can’t even keep up with the number of species.

Because there are so many organisms in the world, it is very important to be able to figure out how all of them are related. In order to do this, we use biological classification. The different levels of biological classification are often accepted to be, in order:






According to many scientists, there are five major kingdoms: Animals, Plants, Fungi, Protists, and Monera. This means that all organisms must fit into one of these kingdoms. For example, we are in the Animal kingdom, trees and bushes are in the Plant kingdom, mushrooms and yeast are in the Fungi kingdom, amoebas are in the Protist kingdom, and bacteria are in the Monera kingdom. Within each kingdom, there are phyla (the plural of phylum). For example, the Animal kingdom has over 9 major phyla, among them Chordata (like us), Insects, Arachnids (spiders) and Arthropods (crabs). Then, there are several classes in the Chordata phylum, like Birds, Mammals, Reptiles and Amphibians.

As you can see, every step you take on the classification list, the more specific it is. Once you get down to the species level (like Homo sapiens), there is only one type of organism. This organization of things is called a hierarchy because it lists the category that has the most things first, and the category with the least things last.

Another view of classification, with the human classification on the right

Just as importantly, you can tell a lot about an organism based on where it’s classified. Because we and dogs are both in the same class (Mammals), that means that we are more closely related to dogs than we are to spiders, as spiders are in a different phylum (Arachnids). If two organisms are in the same genus, that means that they are very highly related. If they are only in the same kingdom, then that means that they are not very highly related at all.

1. List the order of biological classifications.
2. Which classification is:
a) The most general?
b) The most specific?
3. What are the five kingdoms of living things?
Put it together
4. A scientist hands you three insects, named Amber, Bill and Carlos. She tells you that Amber and Bill are in the same family, while Amber and Carlos are in the same order.
a) Which insects are most closely related?
b) Why?
5. Differentiate (tell the difference between) birds and reptiles in two ways.
Think about it
6. Create a new kingdom of living things that does not exist.
a) Describe at least three characteristics of your new kingdom.
b) Sketch one of the organisms.
c) Name the kingdom using the Latin and Greek roots.

10. Define gene frequency.
Classification: Your Own Key

From Wendy Zielinski

  1. Find at least seven images from a magazine that are somehow related.
  2. Arrange the images into two groups based on some difference. Write two questions that would describe the difference between the two groups. Many times, questions are opposite of each other. One answer leads to question 2, one answer leads to question 3.
  3. Take the group described by the answer that leads to question 2 and divide that group again based on a different characteristic. Write another 2 questions to describe the difference.
  4. Continue dividing the groups and writing the questions until all of the images have been described and labeled with a two-word name.
  5. Glue your images to a piece of paper and number each one. This is your poster. Make an answer key for your images.
  6. The answers you are expecting need to be factual. Final names do not have to be factual.
  7. Turn in your poster, your questions and your answer document.
  8. Once your project is in, you will be grading a classmate’s key and someone will be grading yours.
  9. Grade according to the following rubric:
    1. Your name:
    2. Key you’re grading:
    3. A minimum of seven pictures (2 points each):
    4. Pictures numbered (1 point each):
    5. Key has 2 questions per number (2 points each set of questions):
    6. Each answer has a two-word name (2 points each answer, 1 point for one name):
    7. Each picture was able to be identified through the questions (2 points each):
    8. Neatness (6 points possible, 3 for poster, 3 for questions):
    9. Total points:
Dichotomous Keys: Beans
  1. Get a set of beans and a dichotomous key. For each bean:
  2. Write down each decision that you make (e.g., “It is not round”, “It is all white”)
  3. Write down the name of the bean
  4. Identify which beans were not in your set, but were in the dichotomous key. What would you expect each bean to look like, according to the information in the dichotomous key?

[Note: You need an animal card to complete this assignment – and hand it back in when you’re done!]

  1. Put these classifications in the correct order: Order, Species, Kingdom, Class, Genus, Phylum, Family
  2. Come up with a way to remember the order of these classifications, for example: “King Phillip Came Over For Great Sandwiches”. You can make a phrase like this, a drawing, or any other way that includes every classification and helps you remember the classifications. When you hand in the homework, you will be quizzed on the seven classifications (it is worth 7 points of the grade), so don’t just copy off of someone else!
  3. Using the animal card, identify all seven classifications for this animal (if the phylum is missing, it’s “Vertebrates”) keeping in mind that the genus and species are directly below the animal’s name on the back of the card.
  4. Answer:
    1. Which classification contains the most animals?
    2. Which classification contains only one animal?
    3. What is the relationship between the order of the classifications and the amount of animals in each classification?
Dichotomous Keys: Trees
  1. For each of four different trees:
  2. Follow the dichotomous key below for each decision you make.
  3. Write down each decision and the name of the tree, for example:
    Tree #1: 1b, 2b, 6a = Locust
1a. Tree has green leaves (evergreen) Go to 9

Seed Pods

Scale-like, Needle-like, Awl-like

1b. Tree has no leaves Go to 2
2a. The branching is opposite Go to 3
2b. The branching is alternate Go to 6
3a. Buds are red
3b. Buds are dry and scratchy Go to 5
4a. Bark has diamond patterns Norway Maple
4b. Bark is smooth to flaky Red Maple
5a. Bark has diamond patterns White Ash
5b. Bumpy bark with sharp buds Sugar Maple
6a. Twig has seed pods Go to 7
6b. Twig has no seed pods Go to 8
7a. Twig has flat seed pods Locust (Black or Honey)
7b. Twig has round, prickly seed pods Sweetgum
8a. Twig has tiny, cone-like berries Alder or Birch
8b. Twig has fuzzy berries Sumac
9a. Leaves are Awl-like or Scale-like Go to 10
9b. Leaves are Needle-like Go to 11
10a. Leaves are very sharp Juniper
10b. Leaves are not very sharp Falsecypress
11a. Needles are flat with white stripes Go to 12
11b. Needles are bundled Pine
12a. Needles are more square than flat Spruce
12b. Needles are more flat than square Hemlock
Moth Classification


The Manduca sexta, like all insects, has certain characteristics. Those characteristics are:

  1. A body divided into three parts (head, thorax and abdomen)
  2. Three pairs of legs
  3. Usually one pair of antennae and a pair of compound eyes (a few exceptions to these characteristics are found)
  4. Usually two pairs of wings (absent in many insects such as lice, fleas, ants; flies have one pair of wings)

In this lab, you will be identifying all of the different parts of both the caterpillar and the moth, in addition to any other insects present in class. We will have a collection of insects borrowed from the Willis lab at Case Western Reserve University.



  • Hand Lens
  • 1 Caterpillar
  • 1 Moth
  • Pencil
  • Paper




  1. Using the caterpillar, turn it so that its ventral surface (underside) is facing you. Make a sketch of the caterpillar, showing all of the sections, starting with the head and ending with the terminal proleg. Clearly label:
    1. The head, thorax and abdomen
    2. The three pairs of legs
    3. The antennae
    4. Any other significant body part you notice (e.g., the prolegs)
  2. Using the moth, turn it so that its ventral surface (underside) is facing you. Make a sketch of the moth, showing all of the same sections as the caterpillar. With the moth, however, you will also label where the wings join the thorax.
  3. Keeping your two drawings side by side, clearly demonstrate with arrows which parts of the caterpillar develop into which parts of the moth.
  4. Repeat step #1 for all insects available for identification. Make sure that you have at least five observations for each organism.



  1. Make a comparison chart for the different organisms that you observed. You should have a header row and a row for each organism. The columns will be the characteristics that you observed (at least five). Inside the chart, you should put check marks or descriptions that show which organisms demonstrated which characteristics.
  2. Why do you think that you saw the similarities between organisms that you did?
  3. What do these similarities tell us about how related these organisms are to each other?
  4. Add another row to the chart, and use a human as the organism. What are the major differences?
  5. Assume that a scientist finds an organism that has three body segments: head, thorax and abdomen. It also has antennae, two pairs of wings, but only two pairs of legs. What are two possible inferences that scientist could make?
  6. According to the characteristics of insects, create a new insect by sketching something from your own imagination. Make sure that it has all of the necessary parts, then label those parts and name your organism!
Insect Dichotomous Keys


In this lab, you will be identifying similarities and differences between several preserved insects. These insects are fragile, however, so you should treat them with care. The insects have been provided by the entomology lab at Case Western Reserve University and have been collected from locations all around the United States.



  • Hand Lens
  • 10 – 15 mounted insects, labeled with a letter each
  • Pencil
  • Paper



  1. What are some characteristics of all insects that you know?
  2. What are some characteristics of some insects that you know? In other words, what are some things that a few insects possess but others do not? What are some differences in behavior between different insects?
  3. Get a set of 10 – 15 mounted insects. Refer to the letters when writing or talking about the insects, since we are not concerned about their scientific names right now. Observe your insects with the hand lens to get a better idea of some of the less visible parts of their anatomies.
  4. While looking through the insects, determine at least seven characteristics that could be used to split the set into two groups. For example, you could say a characteristic is “Spots on Wings” and you might determine that:


Has Spots on Wings A, B, D, E, H, L, N
No Spots on Wings C, F, G, I, J, K, M


For each of the seven characteristics you identify make a table like the one above.

  1. Choose which one of your seven characteristics is the best. The best one should split your set into half as closely as possible and should be something that anyone with no knowledge of insects could determine.
  2. Use the characteristic from #5 to start your dichotomous key.
    1. Label each step of your dichotomous key with a question, where the answer to that question leads to another step.
    2. As you are doing this, separate your insects into the groups you have divided them into, so you can see which insects you still need to divide up.
    3. If there are no more questions to ask, because there is only one insect left in the subgroup you have created, write the letter of the insect.
    4. Continue until you have classified every insect!



  1. Switch stations with another group. Use their insects and their dichotomous key to classify each insect. If you disagree with a classification, or you think it’s not specific enough, write down what you disagree with on a separate sheet of paper.
  2. After you and the other group are done classifying, make any improvements or changes that the other group suggested, then switch places with a second group. Again, if you disagree with a classification, write down what you disagree with on a separate sheet of paper.
  3. What did you learn was hard about classifying these insects? Write down at least two things that were difficult.
  4. Do you think you could use your dichotomous key for any insect that you found outside? Why or why not?
  5. Why do scientists use dichotomous keys?