1. Modern Taxonomy
Chapter 15, Section 4

2. What is Taxonomy?
The branch of biology involving the identification, naming, and classification of species

3. The Linnaean System of Classification
Carolus Linnaeus ( ) developed a naming system that gave every species a 2-part Latin name and organized them into broader categories
“binomial nomenclature”
Example: Homo sapiens or Homo sapiens

4. Linnaean Classification Groups

5. Taxonomy and Evolution
Darwin used Linnaeus’s to show evolutionary relationships → phylogenetic trees
The more homologous structures organisms shared, the more closely related they were
Today we use molecular evidence, as well as homologies and physical characters to determine ancestry

6. Phylogenetic Trees & Cladograms

7. What’s the Difference? Cladogram Phylogenetic tree Both
Often include Derived Characters or unique features that unite organisms in a clade
Lacks information about the duration of lineages and/or amounts of evolutionary change
Phylogenetic tree
Indicates evolutionary timescale & degrees of change by the length of lines or numerical differences
Both
Illustrate a hypothesis about the common ancestry of life

8. Molecular Phylogeny Comparison of cytochrome c mutations Human
Fig. 10.5

9. Fig. 32.7

10. How to read a Cladogram/Tree
This diagram shows a relationship between 4 relatives. These relatives share a common ancestor at the root of the tree.
Note that this diagram is also a timeline. The older organism is at the bottom of the tree.
The four descendants at the top of the tree are DIFFERENT species. This is called SPECIATION.
DESCENDANTS
Stress that cladograms not only serve as a pictorial representation of lineage, but also as a snapshot in time.
Be sure to introduce the term SPECIATION. The four descendents are DIFFERENT species.
Image courtesy of

11. The event that causes the speciation is shown as the fork of the “V”.
Branches on the tree represent SPECIATION, the formation of a new species.
The event that causes the speciation is shown as the fork of the “V”.
Image courtesy of

12. Species B and C each have characteristics that are unique only to them.
But they also share some part of their history with species A. This shared history is the common ancestor.
Image courtesy of

13. A CLADE is a group of organisms that come from a common ancestor.
If you cut a branch of the tree, you could remove all the organisms that make up a CLADE.
Students should be able to decide if a group of organisms form a clade.
Image courtesy of

14. What is the only thing A and B have in common?
Be sure to have students justify their answer to the question.
Image courtesy of

15. Look at the cladogram at the right
Look at the cladogram at the right. What conclusions can be drawn about the relationship between humans and chimps?
How many clades are in this cladogram?
SEVEN
Image courtesy of

16. Cladistics (How biologists make cladograms)
Organisms in a clade share a derived character
Ex: horse & monkey have hair and mammary glands so they are in the same clade
If an organism does not share the character that unites a clade, it is placed in broader, inclusive clade
Ex: lizard does not have hair or mammary glands, but does have 4 legs and amniotic eggs

17. Cladistics (cont.)
Biologists often use Venn Diagrams to help organize clades, then draw the cladogram
The diagram to the right shows 5 different ways to represent a single line of descent in a cladogram

18. SPECIAL NOTES:
Some characters can derive in unrelated clades due to convergent evolution (analogies)
The hypothesis with the fewest derivations or steps usually is the accepted hypothesis

19. Kingdoms and Domains
Biologists use the largest taxons to show common ancestry among all of life on Earth (past and present)
The number of kingdoms and the formation of domains have changed in response to new discoveries and evidence

23. Classification of Living Things
Domain
Bacteria
Archaea
Eukarya
Kingdom
Eubacteria
Archaebacteria
Protista
Fungi
Plantae
Animalia
Cell Type
Prokaryote
Eukaryote
Cell Structure
Cell walls with peptidoglycan
Cell walls without peptidoglycan
Some have cell walls of cellulose; some have chloroplasts
Cell wall of Chitin
Cell walls of cellulose; chloroplasts
No cell walls or chloroplasts
Number of Cells
unicellular
Most unicellular; some colonial; some multicellular
Most multicellular; Some unicellular
multicellular
Mode of Nutrition
Autotroph or Heterotroph
Heterotroph
Autotroph
Examples
Streptococcus; E. coli
Halophiles, Methanogens
Amoeba, Paramecium, slime molds
Mushrooms, yeast
Mosses, ferns, flowering plants
Sponges, worms, insects, fish