1. The Tree of Life
Chapter 17

2. The Linnaean System of Classification
Living things must be described
1.5 million identified and named species
Identification and naming requires organization
Classification systems provide this organization
Taxonomy – science of naming and classifying organisms
Before the Linean system scientists named newly discovered things however they wanted, often after themselves

3. The Linnaean System of Classification
Each group of organisms is called a taxon (taxa)
Basic level is the species
Any group of animals that can interbreed
In the Linnean System, each species got a name
Still in use today

4. The Linnaean System of Classification
Carolus Linnaeus – Father of taxonomy
Developed two word naming system – Binomial Nomenclature
Always written in italics or underlined
Musca domestica or Musca domestica
First word is the genus, second is the species

5. The Linnaean System of Classification
Common names vary too much
First attempts described physical characteristics
What are the flaws of this method?
Too long of descriptions
Too many varying observations
A name might be twenty words long
United kingdom refers to buzzards as meaning a hawk, US means a vulture

6. The Linnaean System of Classification
Linnaeus’s system consisted of 7 levels
Domain (Largest)
Kingdom
Phylum
Class
Order
Family
Genus
Species (Smallest)
Each level is called a taxon (taxa)
Linnaeus had everything but the domain

7. The Linnaean System of Classification
Levels up always group more organisms together
Families are grouped into orders
Classes are composed of similar orders
Classes make up phylums
Linnaeus had two kingdoms – animalia and plantae

8. The Linnaean System of Classification
Linneaus created his system based on physical similarities
Flaws?
Today scientists genetic information to be sure of similiarities
Two unrelated species can evolve similar traits through convergent evolution

9. Classification Based on Evolutionary Relationships
Anything above species has been “invented”
How would Linnaeus classify these:
Dolphin
Hermit crab
Sparrow
Cow
Snake
Monkey
Bull Shark
Scientists have created levels above species to create order

10. Classification Based on Evolutionary Relationships
Phylogeny – evolutionary relationships among organisms
Used now instead of physical similarities
Evolutionary classification
Species in the same genus are more related than species from another genus

11. Classification Based on Evolutionary Relationships
All members of genus share a common ancestor
This can be traced through a phylogenic tree
The higher the level, the farther back the ancestor
The more recent the common ancestor, the more related
Members that appear similar may not have a common ancestor even though appearnce would suggest so.

12. Classification Based on Evolutionary Relationships

13. Classification Based on Evolutionary Relationships
Cladogram – using derived characters to determine evolutionary relationships
Clade – group of species that share a common ancestor
Derived Characters – characters in recent members, but not older members
Result of evolution
Demands force new innovations
Cladograms are useful in determining how one group branched from another in terms of evolution
The more closely related a species, the more derived characters they share

14. Classification Based on Evolutionary Relationships
Cladogram Interpretation
Derived characters
Nodes – where a branch splits off
Identifying clades – snip rule
What is the derived character of:
Amphibians
Crocodiles and birds
Snip rule – if you snip off before a node, you are left with a clade

15. Classification Based on Evolutionary Relationships
A lot of classification methods are based on appearance
USUALLY, this works…why?
DNA/RNA/Proteins are similar in related species
These substances are used to make comparisons
The more related the DNA is to another organism, the more recently related the organisms are
Organisms that appear the same, more than likely will be related because genes determine appearance, however there are animals that can be related that do not look alike

16. Classification Based on Evolutionary Relationships

17. Molecular Clocks Evolutionary time can also be measured with DNA
Molecular Clock – use DNA mutations to estimate the length of time species have been evolving
Scientists have found mutations tend to occur at constant rates for a species
Relies on mutations to repeat
The more time has passed between two species diverging from a common ancestor, the more mutations there will be
Not just one clock running at a time
Mutations cause a change in the DNA structure – under the pressure of natural selection
More than one molecular clock running at a time

18. Molecular Clocks Molecular Clocks and Real Time
Linking of mutations occurs with geological events and fossil evidence
Amino acid differences along with geological splits determines the evolutionary time

19. Molecular Clocks Different genetic molecules mutate at different rates
Some sequences of DNA mutate rapidly, while others are relatively slow
Mitochondrial DNA
Ribosomal RNA
Found only in mitochondria
Mutation rate is 10x faster than nuclear DNA
Good for closely related species due to speed
Always inherited from mother
Used to study human lineage for 200,000 years
Contained in ribosomes
Good for distantly related species
Low mutation rate

20. Domains and Kingdoms Linnaeus started with two kingdoms:
Plantae
Animalia
Scientists realized they needed more
This lead to five kingdoms
1866 – Ernest Haeckel realized that single celled organisms needed their own kingdom and made protista
1938 – Herbert Copeland argued prokaryotes were different enough to deserve their own kingdom – Monera
1959 – Robert Whittaker felt that because of the feeding habits of fungi they deserved their own kingdom – Fungi
1977 – Carl Woese found that there were two genetically different types of bacteria leading to the split of monera in to bacteria and archaea
Plantae = plants
Fungi = fungus
Anamalia = animals
Protists = are singled celled organisms
Monera = bacteria

21. Domains and Kingdoms Domains – larger and includes the kingdoms
Three domains
Eukarya
Archaea
Archaebacteria
As more discoveries are made, more kingdoms may be made
Because of Woese’s research there are now three accepted domains
Eubacteria = archaebacteria

22. Domains and Kingdoms Domain Bacteria Unicellular Prokaryotic
Thick, rigid cell walls around a cell membrane
Cell wall made of peptidoglycan

23. Domains and Kingdoms Domain Archaea Unicellular Prokaryotic
Live in extreme environments
Volcanic hot springs
Brine pools
Black mud devoid of oxygen
Lack peptidoglycan

24. Domains and Kingdoms Domain Eukarya All organisms have a nucleus
Consists of four kingdoms
Protista
Fungi
Plantae
Anamalia

25. Domains and Kingdoms Kingdom Protista
Members have the greatest diversity
Cannot be classified as animals, plants, or fungi
Most single celled organisms
Some are multi-celled algae
Some are photosynthetic

26. Domains and Kingdoms Kingdom Fungi All are heterotrophs
Feed on dead or decaying organic matter
Most recognizable is the mushroom
Most are multicellular, others (Yeast) are unicellular

27. Domains and Kingdoms Kingdom Plantae Multicellular
All are photosynthetic autotrophs
Non-mobile

28. Domains and Kingdoms Kingdom Anamalia Multicellular Heterotrophs
Mobile
Incredible diversity