Part 3: Analyzing Cladograms & Dichotomous Keys Classification Part 3: Analyzing Cladograms & Dichotomous Keys

Cladograms A branched diagram that shows the relationships among organisms, including common ancestors. Each branch follows a new characteristic. Each characteristic is observed in all the species to its right. Example: The salamander, lizard, hamster, and chimpanzee have lungs, but the salmon does not. Therefore, they are more closely related to each other than they are to the salmon.

Analyzing Cladograms Which organisms are more closely related, the dragonfly and butterfly or the ant and grasshopper? Why? Which organisms are more closely related, the inch worm and fly or the fly and dragonfly? Why?

Dichotomous Keys A series of descriptions arranged in pairs that lead the user to the identification of an unknown organism.

Teeth visible …. Go to 2 Teeth not visible … Go to 4 Smiling, happy … Smilus traditionalis Not happy … Go to 7 Has a toothy smile …Smilus Toothyus Is not smiling … Go to 3 Mouth curved down … Smilus saddus Mouth is small circle … Smilus suprisus Visibily crying … Smilus dramaticus Frowning … Smilus upsettus Has an eye patch … Smilus piratus No eye patch … Go to 9 Eyes are Symmetrical … Go to 5 Eyes not Symmetrical … Go to 8 One eye is much larger … Smilus mutates One eye is winking … Smilus winkus Eyes heart shaped … Smilus valentinus Eyes oval shaped … Go to 6