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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
