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
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
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
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 cat cat sponge salmon earthworm lizard kangaroo amoeba salmon salmon earthworm lizard lizard kangaroo kangaroo
cat salmon earthworm lizard kangaroo sponge Multicelled amoeba
cat cat cat salmon salmon salmon earthworm lizard lizard lizard kangaroo kangaroo kangaroo earthworm earthworm sponge sponge amoeba Segmented Multicelled sponge amoeba Multicelled
cat Segmented Jaws lizard kangaroo salmon earthworm sponge amoeba Multicelled
cat lizard salmon earthworm sponge Limbs amoeba Segmented Jaws Multicelled kangaroo lizard salmon earthworm earthworm sponge sponge sponge amoeba amoeba amoeba
cat kangaroo lizard salmon earthworm sponge Limbs Hair amoeba Segmented Jaws Multicelled
cat kangaroo lizard salmon earthworm sponge Limbs Hair Placenta amoeba Segmented Jaws Multicelled