CLADOGRAM ANALYSIS
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
3. ______ Segmented Body
5. ______ Cerci (abdomenal appendages)
7. ______ Legs
2. ______ 6 Legs
4. ______ Double set of wings
6. ______ Crushing mouthparts
8. ______ Curly Antennae
Part II Constructing a Cladogram
Objective: Students will construct a cladogram using descriptions and
information about 7 imaginary animals. Students will determine which traits
are derived traits, and identify synapomorphy and automorphy of
characteristics.
Tips for constructing your cladogram
1. Use the times to determine the positioning of the species. Older
organisms will appear first on the cladogram
2. Determine features that are shared among organisms - these are
synapomorphies - Place an S on these features to help you keep track
3. Determine features that are unique to organisms - these are
automorphies - Place an A on these features
4. There may be several ways to represent this cladogram, remember that
cladistics and systematics is inexact, do not worry if yours looks different
from others.
5. Draw your cladogram on at the bottom of the chart
Description of Species
Species 1 - Fossils of this species date back to 30,000 years
ago. The organism has a single antenna that is branched (like
a Y). It has two eyes positioned on top of the head a non
segmented body
Species 2 - Fossils of this species date back to 8,000 years
ago. This organism has branched antennae, 3 body segments,
the middle segment has fleshy appendages with a bendable
joint.
Species 3 - Fossils of this species date back to 25,000 years
ago. The organism has a branched antenna (like a Y), body is
divided into 2 segments, and eyes positioned on the top of the
head. In addition, the last segment of the body has a long
curley tail.
Picture
Species 4 - Fossils of this species date back to 10,000 years
ago. This organism has branched antennae, 2 body segments,
eyes positioned on the top of the head, fleshy appendages on
the last segment have a bendable joint.
Species 5 - Fossils of this species date back to 50,000 years
ago. The organism has a single antennae, two eyes positioned
on top of a head and a non segmented body.
Species 6 - Fossils of this species date back to 20,000 years
ago. This organism has branched antennae, 2 body segments,
eyes positioned on the top of the head, and small flesh
appendages on the last segment. This organism also has a
ridge of spines on the last segment.
Species 7 - Fossils of this species date back to 31,000 years
ago. The organism has a single branched antennae (like a Y)
and a club like structure at the end of the branches of the
antennae. It has two eyes positioned on top of the head and a
non segmented body.