1. Understanding the Dynamic Nature of Classification
Kristine Levesque

3. Taxonomy
Western Science describes taxonomy: classification according to the presumed relationships among organisms
Identify organisms
Recognizing natural groupings
2 – 4.5 million living things
4x as many that are already extinct

4. Early Classification Schemes
Early historical documents show that living things were divided into plants and animals
Plants divided into grasses, hedges and trees
Animals divided into fish, creeping creatures, fowl, beasts, and cattle

5. People who Classified
Aristotle: grouped animals according to the kind of environment they lived in
Air-dwellers – butterflies, birds, bats, etc.
Land-dwellers – elephants, lizards, worms, etc.
Water-dwellers – crabs, starfish, etc.

6. Theophrastus: grouped plants according to stem structure
Herbs (soft), shrubs (several woody stems), and trees (a single woody stem)
John Ray: classified organisms on the basis of structural similarities
Species – groups of organisms that are structurally similar, able to interbreed and produce fertile offspring

7. Classification
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species

8. Phylogeny: the evolutionary history of a species.
Carolus Linnaeus: methods for classifying and naming organisms that are still used today.
Often referred to as the “Father of Taxonomy”
Taxonomy: arrangement of organisms into groups based on evolutionary relationships between different organisms.
Phylogeny: the evolutionary history of a species.

9. Evidence used in Classification
Biochemistry: the comparison of organisms’ proteins, amino acid sequences, DNA and RNA.
Can determine the degree of genetic similarity among organisms

10. Comparative morphology: comparison of the structure of organisms
May not be enough to accurately identify or classify an organism

11. Embryology: similarity and differences of embryonic structures and tissues to determine relatedness of organisms
Similar structures can sometimes come from different embryonic tissues, and different structures can come from similar tissues.

12. Chromosome/Genetics: comparison of the chromosomes of different organisms. Similar genetic makeup is a clue to a common ancestor.

13. Grouping Species
Domain: the broadest category in the classification system
Bacteria – prokaryotes, cell walls have peptidoglycan, most abundant
Archaea – ancient bacteria, no peptidoglycan in cell walls, extremophiles
Eukarya – membrane bound nucleus, all eukaryotes, contains kingdoms protista, fungi, plantae, and animalia

14. The Kingdom System
An attempt by humans to impose order on a vast, diverse group of organisms.
This means that not all organisms fit into the kingdoms.
The kingdom system tries to reflect evolutionary relationships.

15. The kingdoms are identified as Protists, Fungi, Plants and Animals
The system is based on the following criteria:
The number of cells in an organism/tissue structure
Cell structure/cell type (presence or absence or true nucleus or organelles)
The mode of nutrition/energy source
Developmental patterns/reproduction

16. Classification Systems
Most common systems of classification today are based on a method of analysis called cladistics.
Ancestral traits
Derived traits

17. Cladograms

18. Binomial Nomenclature
The genus first and is capitalized.
The species name follows and is NOT capitalized.
Both words appear in italics or are underlined.
E.g. Canis latrans, Canis lupus
Canis latrans, Canis lupus

19. Binomial Nomenclature
A common name:
Can be confusing
Different languages
Many different names
Canis familiaris

20. Dichotomous Key A dichotomous key
determine the identity of items in the natural world,
Dikho – Greek – in two
Temnein – to cut dikhotomos  dichotomous (late 17th century)