How Does a Cladogram Reveal Evolutionary Relationships?
What is a cladogram? It is a diagram that depicts evolutionary relationships among groups. It is based on PHYLOGENY,
which is the study of evolutionary relationships. Sometimes a cladogram is called a phylogenetic tree (though technically,
there are minor differences between the two).
In the past, biologists would group organisms based solely on their physical appearance. Today, with the advances in
genetics and biochemistry, biologists can look more closely at individuals to discover their pattern of evolution, and group
them accordingly - this strategy is called EVOLUTIONARY CLASSIFICATION
CLADISTICS is form of analysis that looks at features of organisms that are considered "innovations", or newer features
that serve some kind of purpose. (Think about what the word "innovation" means in regular language.) These
characteristics appear in later organisms but not earlier ones and are called DERIVED CHARACTERS.
PART I-Analyze the Cladogram
Examine the sample cladogram, each letter on the diagram points to a derived character, or something different (or
newer) than what was seen in previous groups. Match the letter to its character. Note: this cladogram was created for
simplicity and understanding, it does not represent the established phylogeny for insects and their relatives.
1.______ wings
2.______6 legs
3._______segmented body
4. ______double set of wings
5.________ legs
6._________crushing mouth parts
7._________curly antennae
8.________cerci (abdominal appendages)