1. Classification of Living Things
Chapter 20

2. Taxonomy Identifying, naming and classifying organisms Latin base
Aristotle
first to classify, divided into 14 major
Categories
Subdivided them according to size
John Ray
All organisms should have a set name
Divided them into groups based on how
he thought they were related

3. Carolus Linnaeus 1707 - 1778 Binomial nomenclature – 2 part name
Genus – contains many species
Specific epithet (1 species)
Usually descriptive, can have geographic descriptions
When writing a scientific name
Genus capitalized
Species lower case
Italics, underlined if handwritten
Published Systema Naturae in 1735

4. species Interbreed and share the same gene pool Subspecies
Variant types of organisms of a species that tend to interbreed where their populations overlap
They could actually be different species
hydridization

5. Classification categories
Species
Genus
Family
Order
Class
Phylum
Kingdom
Domain
More than 30 categories: super, sub, infra
Organisms put in categories based on characters, structural, chromosomal, or molecular features

6. Phylogenetic trees
Systematics – study of the diversity of organisms at all levels of organization
Taxonomy and classification
Goal: determine phylogeny – evolutionary history
Represented by Phylogenetic tree
Shows divergence from a common ancestor
Derived characters – individual characteristics

7. Tracing phylogeny Record data from:
Fossil evidence
Homology
Molecular data
Using this information you can determine common ancestors and classify organisms accordingly

8. Homology Includes comparative anatomy and embryological evidence
Sometimes homology is challenging because of
Convergent evolution – having the same or similar characters but distantly related due to adaptation to the environment
Analogous structures – having same function but do not have common ancestor (wings of bat/insect)
Parallel evolution – similarity in structure in related groups that cannot be traced to common ancestor

9. Molecular data Protein comparisons - limited RNA and DNA Comparisons
DNA-DNA hybridization: compare single strands from different organisms and allowed to combine, if closely related, strands will stick together
Nucleotide sequences
Molecular clocks – nucleic acid changes used to indicate relatedness and evolutionary time

10. Cladistic Systematics
Willi Hennig
Uses shared derived characters to classify organisms and construct a cladogram
Objective because it lists characters used to construct cladogram
Figure 20.11, table 20.2

11. Phenetic systematics
Species are classified by the number of their similarities
Count the # of traits the two species share and estimate the degree of relatedness
Figure 20.10

12. Traditional systematics
Mainly use anatomical data to classify organisms
Stress common ancestry and degree of structural difference among divergent groups
Not as strict as cladists

13. Classification systems
Began with 2 kingdoms: animal and plant
1880 Ernst Haeckel:
Added kingdom Protista
unicellular, microscopic
1969: RH Whittaker – expanded system to 5 kingdoms: monera, protista, fungi, plantae and animalia
Based on type of cell, complexity, type of nutrition

14. 3 Domain system Late 1970’s Carl Woese Used rRNA sequencing
Proposed 2 groups of prokaryotes because they were so different
Domains:
Archea – prokaryotes that are not bacteria
Bacteria – mostly prokaryotic bacteria
Eukarya – contains Protista, Fungus, Plantae and Animalia