Analyzing Relationships Between Species

Lesson Plan - Get It!

Audio:

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

There are many different types of living organisms on the 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.

_{Image released under the GNU Free Documentation License}

• Where would earthworms go in the diagram 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:

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

Watch Cladograms, from Bozeman Science, to find the answers:

Cladograms are used to show the existing relationships among species living on the 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.

Move on to the Got It? section where you will practice reading cladograms.