18-2 modern evolutionary classificationdr-priestley.com/btsd/bio/c18s2.pdf · slide 12 of 24...
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18-2 Modern Evolutionary Classification
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18-2 Modern Evolutionary Classification
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Evolutionary Classification
Evolutionary Classification
Phylogeny is the study of evolutionary relationships among organisms.
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Evolutionary Classification
Biologists currently group organisms into categories that represent lines of evolutionary descent, or phylogeny, not just physical similarities.
The strategy of grouping organisms is based on evolutionary history and is called evolutionary classification.
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Evolutionary Classification
The higher the level of the taxon, the further back in time is the common ancestor of all the organisms in the taxon.
Organisms that appear very similar may not share a recent common ancestor.
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Evolutionary Classification
Different Methods of Classification
Appendages Conical Shells Crustaceans Mollusk
Crab Barnacle Limpet Crab Barnacle Limpet
Molted external skeleton
CLASSIFICATION BASED ON VISIBLE SIMILARITY CLADOGRAM
Segmentation Tiny free-swimming larva
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Classification Using Cladograms
Classification Using Cladograms
Many biologists now use a method called cladistic analysis.
Characteristics that appear in recent parts of a lineage but not in its older members are called derived characters.
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Classification Using Cladograms
Derived characters can be used to construct a cladogram, a diagram that shows the evolutionary relationships among a group of organisms.
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Classification Using Cladograms
A cladogram shows the evolutionary relationships between crabs, barnacles, and limpets.
Crustaceans Mollusk
Crab Barnacle Limpet
Tiny free-swimming larva
Molted external skeleton Segmentation
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Similarities in DNA and RNA
Similarities in DNA and RNA
The genes of many organisms show important similarities at the molecular level.
Similarities in DNA can be used to help determine classification and evolutionary relationships.
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Similarities in DNA and RNA
The genes of many organisms show important similarities at the molecular level.
Similarities in DNA can be used to help determine classification and evolutionary relationships.
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Similarities in DNA and RNA DNA Evidence
The more similar the DNA of two species, the more recently they shared a common ancestor, and the more closely they are related in evolutionary terms.
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Molecular Clocks
Molecular Clocks
A molecular clock uses DNA comparisons to estimate the length of time that two species have been evolving independently.
new mutation
new mutation
2 mutations
A B C
A gene in an ancestral species
Species Species Species
new mutation
2 mutations
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