Taxonomy & Classification

Taxonomy- science of identifying and classifying organisms; all about the naming

Classification- systematic grouping and naming of organisms based on shared similarities

Systematics-

PubMed Search on 9/8/08

“tree of life” AND 2008

47 articles so far this year

Why classify?

“Planet Bob”

How to classify?

Taxonomy & Classification

Taxonomy- science of identifying and classifying organisms; all about the naming

Classification- systematic grouping and naming of organisms based on shared similarities

Systematics- study of the diversity of life and relationships between organisms

How to classify?

We now have 8 Kingdoms.

(by some accounts)

•No modern technology

•How to classify living organisms?

4th century B.C. The Age of Aristotle

4th century B.C. The Age of Aristotle

•No modern technology

•2 Divisions

•Plants (immobile)

•edible vs. inedible

•Animals (mobile)

•blood vs. bloodless

•walking vs. flying vs. swimming

•Used up through 1600s

•In use through 1600s

1500s to 1600sThe Age of Exploration

• Extensive travel to New World

• Push to collect/classify as many specimens as possible; many newly discovered organisms

• “free for all”- long descriptive names, “folk taxonomy”, duplicate names for same organism, one organism with 2 names, etc.

• Tomato- Solanum caule inermi herbaceo, foliis pinnatis incisis (solanum with the smooth stem which is herbaceous and has incised pinnate leaves)

1700s:The Age of Carolus Linnaeus (born

Carl von Linne)

• “Father of Modern Biological Classification”

• Standardized classification

• Binomial nomenclature (Genus species)

• Hierarchy: Kingdom, Phylum, Class, Order, Family, Genus, Species

1700s:The Age of Carolus Linnaeus (born

Carl von Linne)• Based on phenetics

• shared physical characteristics

• does not take into account evolutionary relationships, fossils, embryology, behavior, etc.

• Solved “folk taxonomy” problem

• pill bug, sow’s ear, roly poly, sowbug becomes Armadillium vulgare

1700s:The Age of Carolus Linnaeus (born

Carl von Linne)

• 2 Kingdoms

• Plantae

• Animalia

1700s-1800s: The Age of Microscopy

• Great advances in microscopes

1700s-1800s: The Age of Microscopy

• Great advances in microscopes

• Ernst Haeckel adds 3rd Kingdom

• From 2 to 3 Kingdoms

• Protista (single-celled eukaryotes and prokaryotes)

• Plantae

• Animalia

• Classification must reflect principle of common descent

• Haeckel coins term phylogeny (classification based on evolutionary relationships)

• “Tree of Life” born

1800s: The Age of Darwin

Early 1900s: The Cladistic Challenge Begins (& continues)

• Clade- group of organisms that share common characteristics and a common ancestor; phylogenetics

• Cladistic analysis- form hypotheses about organismal relationships and test by looking for evidence to support or refute

Early 1900s: The Cladistic Challenge Begins (& continues)• Cladistic analysis

• rely on all available data (morphological, genetic, biochemical, fossil, behavioral, etc.) to test hypothesis• distinguish monophyletic, paraphyletic, polyphyletic

groups

• monophyletic- all members of group share common ancestor

• paraphyletic- some members of group share common ancestor

• polyphyletic- members do not share common ancestor

• Reorganize “Tree of Life” to reflect evolutionary relationships revealed by new evidence

1950s: 3 to 4 to 5 Kingdoms

4 Kingdoms based on phenetics

•Monera (single-celled prokaryotes)

•Protista (single-celled eukaryotes)

•Plantae (mostly autotrophic, multicellular eukaryotes)

•Animalia (multicellular eukaryotes)

(Herbert Copeland)

1950s: 3 to 4 to 5 Kingdoms

5 Kingdoms based on phenetics

•Monera •Protista•Plantae •Fungi •Animalia

(Robert Whittaker)

Mid-late 1900s: The Molecular Age Begins

•Molecular evolution •Molecular clocks•DNA and protein•sequence comparisons

cytochrome c protein sequence alignment

Mid-late 1900s: The Molecular Age•Archaebacteria acknowledged as separate kingdom based on rRNA sequencing (both eukaryote- and prokaryote-like features)(both eukaryote- and prokaryote-like features)

6 Kingdoms •Archaebacteria •Eubacteria•Protista•Plantae•Fungi•Animalia

Based on evolution and molecular genetics (Carl Woese, 1977)

Mid-late 1900s: The Molecular Age

Kingdoms placed into 3 Domains based on molecular genetics (Carl Woese, 1990)

3 Domains •Bacteria•Archaea•Eukarya

Mid-late 1900s: The Molecular Age•Protista further subdivided; many members more like plants or animals than they are each other

8 Kingdoms (and maybe more) •Archaebacteria •Eubacteria•Archaezoa•Protista•Chromista•Plantae•Fungi•Animalia

Based on evolution and molecular genetics

2000 and beyond The Age of Phylogenomics

•Whole genome sequencing•Genome comparisons reveal possible evolutionary relationships•Corroborate horizontal gene transfer•Is it “Tree of Life” or Ring of Life”???•Evidence suggests eukaryotes arose from fusion of archaebacteria with a photosynthetic bacteria•Cladistic analysis continues

Biological systematics not set in stone, in flux

•It is a HYPOTHESIS!!!•Phylogenetic trees vs. rings???•How many Kingdoms???

•Textbooks disagree•We will go with 8

•Phyla being reshuffled•New data becoming available all the time•Hypothesis constantly revised accordingly•Etc.