Cladograms: Evolutionary
Relationships
Cladograms
Cladograms are diagrams that depict the
evolutionary relationships among species using
shared ancestral and derived traits.
◦ The relationships may be based on physical
appearances: phenotypes.
Word origin
Cladogram is derived from the word
clade: a group of organisms that includes
an ancestor and all descendants of that
ancestor. It is a branch on the tree of life.
(Origin from the Greek: klados meaning
branch.)
Traits
Shared derived trait:
◦ a feature that is not found in other groups of
descendants of a common ancestor.
◦ Ex. Hair is a feature shared by mammals, but
not found in non-mammalian vertebrates.
How to build a cladogram
http://ccl.northwestern.edu/simevolution/
obonu/cladograms/Open-This-File.swf
Oldest events are usually at the bottom
with the modern species at the top.
The branches are based on study
including evidence from:
◦
◦
◦
◦
fossil record
comparative anatomy
biochemistry
genetics.
Genetic basis
Based on the data below, which of the following
is more closely related to humans, mushrooms
or tulips?
Percentage differences between sequences
Human
Human
Mushroom
Tulip
Mushroom
0
Tulip
30
40
0
40
0
Nodes
A point on a cladogram where a single
ancestral line breaks into two or more
descendent lines.
Try Building a Cladogram
Lancelet
Lancelet
Lamprey
Salmon
Clouded Salamander
Tree Frog
Red Fox
Lamprey
Salmon
Clouded
Salamander
Tree
Frog
Red Fox
Which point represents the nearest
common ancestor to the gorilla and
elephant?
•Point a is the nearest common ancestor.
In the above cladogram, assume that the ancestor was an herb (not a
tree) without leaves or seeds. Based on the cladogram and assuming
that all evolutionary changes in these traits are shown, which of the
following organisms grows like a tree and lacks true leaves?
a) Lepidodendron
b) clubmoss
c) oak
d) Psilotum
e) fern
Resources
http://www.ucmp.berkeley.edu/IB181/VPL/
Phylo/Phylo2.html
http://evolution.berkeley.edu/evolibrary/ar
ticle/phylogenetics_02
http://ccl.northwestern.edu/simevolution/
obonu/cladograms/Open-This-File.swf