Modern Classification:
Cladograms
SB3c
Explain the evolutionary basis of
modern classification systems
Basis for Modern Classification
• Evolutionary Relationships
– Homologous structures (same
structure, different function)
– Similar embryo development
– Similarity in DNA, RNA, or the amino
acid sequence of Proteins
Homologous Structures show Similarities in
mammals.
Similarities in Vertebrate Embryos
DNA testing to determine
relationships
Cladograms
• Cladogram – diagram that shows
the evolutionary relationships
between organisms
• Derived characters - traits or
characteristics that have evolved
– Individual organisms “branch off”
when they do not share the derived
character in question
Feathers
Let’s try this…
• Cladograms can be constructed for
any group of organisms.
– kangaroo, earthworm, amoeba, lizard,
cat, sponge, and salmon.
• Each of these creatures has an
evolutionary relationship to one
another.
• They all share a common origin.
• their current forms are all derived
from branching events somewhere
in the phylogenetic past.
Complete the characteristic chart
•Use + to indicate the presence of a characteristic in the organism
•Use – to indicate that the organism does not have the
characteristic
segmented
Derived
Characters
kangaroo
earthworm
amoeba
lizard
cat
sponge
Salmon
jaws
hair
placenta
Multicellular
limbs
earthworm
kangaroo
amoeba
lizard
cat
sponge
salmon
Derived
Characters
segmented
jaws
hair
Kangaroo 5
+
+
+
-
+
-
-
+
+
+
-
+
+
+
+
+
+
+
-
+
-
+
+
+
+
+
+
-
Earthworm
2
Amoeba 0
lizard
cat
sponge
Salmon
placenta Multicellula
r
limbs
Ok
• Look at the organisms to see how
many of the derived characters
they share:
– Amoeba has 0
– Sponge has 1
– Salmon has 3
– Etc.
• Using these patterns of shared
derived characters, a cladogram can
be constructed as a series of
branches.
• At every branch, one of the
organisms that does not share a
common character with the rest of
the group is "branched off" into its
own clade.
cat
sponge salmon
earthworm lizard
kangaroo amoeba
cat
sponge salmon
earthworm lizard
kangaroo
amoeba
cat
salmon
earthworm lizard
kangaroo
sponge
amoeba
cat
salmon
earthworm lizard
kangaroo
earthworm
sponge
amoeba
cat
kangaroo
salmon
earthworm
sponge
amoeba
lizard
cat
kangaroo
lizard
salmon
earthworm
sponge
amoeba
kangaroo
lizard
salmon
earthworm
sponge
amoeba
cat
cat
kangaroo
lizard
salmon
earthworm
sponge
amoeba