Banner with text "How to read a cladogram" flanked by two cladograms.
hot to read a cladogram

Reading a Simple Cladogram

Cladograms are a way to organize things by what they have in common. They are a tool scientists use to understand how things are similar and different.

Left-facing cladogram with branches leading to small illustrations of a walnut, plum, peach, tomato, watermelon, orange, and lemon.
Left-facing cladogram.
Left-facing cladogram.
Left-facing cladogram.
Left-facing cladogram.
Left-facing cladogram.
Left-facing cladogram.
Circular icon with the number one in the center.

This node = seeds present

Which fruits have seeds? A walnut, plum, peach, tomato, watermelon, orange, and lemon.

Go to node #2.

Circular icon with the number two in the center.

This node = soft inside

Which fruits are soft inside? A plum, peach, tomato, watermelon, orange, and lemon. Which fruit is NOT soft inside? A walnut.

GET THE IDEA?
Go to node #3.

Circular icon with the number three in the center.

This node = small seeds

Which fruits have small seeds inside with no large central stone, AND are soft inside? A tomato, watermelon, orange, and lemon.

SEE THE PATTERN?
Go to node #4.

Circular icon with the number four in the center.

This node = large central stone

Which fruits have a large central stone, AND are soft inside? A plum and peach.

GETTING ANY EASIER?
Go to node #5.

Circular icon with the number five in the center.

This node = thick skin

Which fruits have thick skin, AND have small seeds inside with no large, central stone, AND are soft inside? A watermelon, orange, and lemon.

ALMOST DONE!
Go to node #6.

Circular icon with the number six in the center.

This node = segmented

Which fruits are segmented, AND have thick skin, AND have small seeds inside with no large, central stone, AND are soft inside?

FIGURE IT OUT!

Click on the numbers to learn how a cladogram of fruit works.

green arrow

Reading the Tree of Life

This cladogram shows some of the groups of species that make up our diverse planet.

Follow the numbers to see how to read the Tree of Life cladogram.

Left-facing rectangular cladogram.
Left-facing rectangular cladogram.
Left-facing rectangular cladogram with branching lines.
Left-facing rectangular cladogram with branching lines.

THIS NODE = LIFE

All living things have cells that can make copies of their own DNA. Which groups of species on this cladogram are alive? All of them!

Go to node #2.

THIS NODE = EUKARYOTES

All eukaryotes have cells with a nucleus that contains most of the cell’s DNA. Which groups of species on this cladogram are alive AND are eukaryotes? All these groups EXCEPT for true bacteria.

GET IT?
Go to node #3.

THIS NODE = BILATERIANS

Some eukaryotes have mirror symmetry; if you draw a line along the length of their body, the right half is a mirror image of the left. These organisms are called bilaterians. Which groups on the cladogram are alive AND are eukaryotes AND have mirror symmetry? All groups listed on the forking cladogram from mollusks to birds.

SEE THE PATTERN?
Go to node #4.

THIS NODE = VERTEBRATES

Some living eukaryotes that are symmetrical also have backbones. They are called vertebrates. Which groups of species are alive AND are eukaryotes AND are symmetrical AND have backbones?

FIGURE IT OUT AND YOU’LL BE A CLADOGRAM EXPERT!

Click on a number to find out what these groups have in common.

Image Credits:

main image, M. Shanley/© AMNH.