Download Modern Taxonomy

Modern Taxonomy
Evolutionary Classification
• Cladistics – the branch of taxonomy that classifies
organisms according to their evolutionary divergence
from common ancestors
• Comparisons
• DNA
• RNA
• Amino acid sequences
• Different results
• Traditional classification
• Key characteristics compared
• Places birds in their own group
• Evolutionary classification
• Structural features and other characteristics
compared
• Reflects closer relationship
• Places birds with crocodiles
Cladograms
• Cladogram – a branching diagram showing points of species divergence
from a common ancestor without indication as to how far removed
species are from each other
• Clade – a group of related organisms representing a complete
branch of a biological tree
• Derived characters – a character shared by all members of a branch but
not present before the branch in cladograms
• Parsimony – the principle that looks for the simplest, and probably most
likely, scientific explanation that fits the evidence
• Strategies for interpreting cladograms
• Step 1 | Determine which members of the group
share a common ancestor
• Step 2 | Determine which organisms are more closely
related by counting the splits between organisms.
• Simplified and may omit species or groups
• Can be drawn multiple ways
• Groups debated
• Differing cladograms
Biology 14.3 – Modern Taxonomy
Modern Taxonomy
Tools Used in Evolutionary Classification
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Fossil record
Biogeography
Anatomy
Biochemistry
• Fossils and biogeography
• Changes over long periods of time
• Living with extinct species
• Radioactive dating
• Comparing anatomy can indicate common ancestry
• Homologous structures suggest similar evolutionary origin
• Biochemistry comparisons
• Amino acid sequences of proteins
• Nucleotide sequences of DNA and RNA
• Mutation clocks – a technique that uses the fossil record and
rates of molecular change to deduce the time in geologic history
when two species diverged
• Greater differences, longer time since divergence from
common ancestor
Biology 14.3 – Modern Taxonomy