Download FIGURE 18.1

What is the Linnaean System of Taxonomy?
• Levels of taxonomy: Kingdom, Phylum (or Division); Class;
Order; Family; Genus and Species
– Today, all levels are intended to reflect evolutionary relatedness
– Developed by Carolus Linnaeus (mid 1700s), a Swedish botanist
• Binomial Nomenclature (Linnaeus, 1758)
– Each species receives a unique scientific name in Latin (common names
differ by location and change over time)
• Latin is a dead language (will not change), and is used internationally
– Scientific names always two words (Genus species), always underlined or
italicized (versus longer description in Latin); second name not used alone,
lower case, often describes location species found or in honor of person
• Tomato (pre-Linnaeus): Solanum caule inermi herbaceo, foliis pinnatis incises
• Descriptions of Newly Discovered Species
– Often identified based on their physical structure (Morphological Species
Concept); taxonomists attempt to include genetic comparisons and
ecological descriptions also (e.g., habitat)
– Holotype and Paratypes: first known specimen and subsequent specimens
described in peer-reviewed scientific journal
Figures 5-2
and 5-3
Figure 5-4
Figure 5-5
Figure
5-7
Cell Types and Shared Structures
• Prokaryotic Cells (Prokaryotes: Eubacteria and Archaea)
– Most 1-10 μm; seen in fossil record by 3.5 bya; lack a nucleus and
other membrane-bound organelles (DNA free in cell, in nucleoid
region)
• Eukaryotic Cells (Eukaryotes: Fungi, Protists, Plants, and
Animals)
– Most 10-100 μm; seen in fossil record by 2.2 bya; have a nucleus
and other membrane-bound organelles
• All Cells Share (thus common ancestor had …)
– Cell (plasma) membrane: a boundary; micelles can form naturally
– Ribosomes: composed of proteins and RNA; bacterial ribosomes
have a different size and structure than those in eukaryotes
– DNA, RNA, and the Genetic Code: bacterial chromosome a simple
ring of DNA; in eukaryotes, DNA is packaged with proteins
– Other molecules / structures: membrane proteins (ex. ATP, ATP
synthase), metabolic enzymes, cytoskeletal tubules and filaments
Figures 5-8
and 5-9
How are Phylogenetic Relationships
Determined?
• Clade: an ancestral species and all of its descendents (a
“branch on the Tree of Life”)
– Cladistics: systematic analysis of clades and their relationships to
other clades; focuses on the evolutionary innovations that define
branch points in evolution (synapomorphies: shared, derived traits)
• Parsimony: convergence considered more rare than homology; tree that
results in fewest number of steps considered most parsimonious
• Techniques
– Often heavy computer memory requirements for statistical tests
(bootstrapping, Monte Carlo simulations, tests of monophyly)
• If multiple trees result with equal significance, relationships remain
unresolved (a “bush”)
• Any single resulting tree still considered a hypothesis; best if consistent
with other independent evidence (e.g., the fossil record)
– Character states entered for multiple traits (ex. horns present = 1,
horns absent = 0); taxa that share more homologies considered
more closely related; nucleotide or amino acid sequences often
used (eliminates potential bias in choice of characters)