Analyzing Relationships Between Species

Contributor: Hannah Brooks. Lesson ID: 12662

A picture is worth a thousand words, especially when it comes to scientific concepts. If you've never heard of a phylogenic tree, maybe you've heard of a cladogram! Read on to learn this useful tool!


Life Science

learning style
personality style
Grade Level
Middle School (6-8)
Lesson Type
Dig Deeper

Lesson Plan - Get It!


What can you learn by looking at pictures of important science concepts? Pictures and charts are often easier to understand than just words. Learn about a simple chart that can help you compare aliens!

Images can be a great resource for learning information in a visual form.

There are many different types of living organisms on Earth today, with great biodiversity. Scientists often group or classify these organisms based on common characteristics like spinal cords, wings, and type of eyes. Scientists use cladograms, or phylogenic trees, to show how these species groups are related. The image below uses branches to show how closely insects are related. Notice how flies and butterflies have the most in common, as shown in the image below. Where would earthworms go?

Image released under the GNU Free Documentation License

As mentioned above, the visual map that scientists use to show species relation is called a cladogram. Cladograms organize organisms based on common characteristics like physical appearance and genetic similarities.

Image released under the GNU Free Documentation License

Reading a cladogram is easy; just look for how closely two organisms are physically located in the image. Look at the image above, a cladogram on plants provided by WikiMedia Commons. How are clubmosses and ferns related? They have the most differences because they are the farthest apart in the image. Flowering plants and ferns are more closely related because they are close to one another. You should also look at the number of branches between two organisms. One split indicates that the organisms are more closely related, while multiple splits suggest more differences.

Some cladograms include what trait the scientist is using to separate organisms. This helps the viewer understand the relationship between the species that are shown.

Watch a short video on how scientists create cladograms, and answer these questions:

  1. What is the first step in constructing a cladogram?
  2. How do you sort organisms in cladograms?

Watch How to Build a Cladogram to find the answers:


Cladograms are used to show the existing relationships among species living on Earth today. These species are classified according to similar characteristics and features like wings, legs, and gills. Scientists use this visual tool to help organize the many species we have in our world.

Discuss what you have learned with a parent or teacher before moving into the Got It? section, where you will practice reading cladograms.

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