1. The Tree of Life
Chapter 17

2. 17.1 Taxonomy The science of naming and classifying organisms
2000 years ago – Aristotle
Grouped plants and animals
Based on structural similarities
Greeks and Romans included categories
Genus = Latin for group

3. Taxonomy Mid – 1700’s Naming organisms Polynomials Descriptive phrases
European honeybee
Apis pubescens, thorace subgriseo, abdomine fusco, pedibus posticis glabis, untrinque margine ciliatus

4. Simpler System Carl Linnaeus Swedish biologist
Developed binomial nomenclature
Two-part naming system
Ex: European honeybee
Apis mellifera

5. Scientific Names Unique two-part name for a species Genus - First name
Taxonomic category of similar organisms
Organisms have common important characteristics

6. Scientific Names Species = Second name
One specific kind of living thing
Identifies the particular type of organism
Most specific and basic naming unit

7. Rules for Scientific Names
Genus
Always first
Capitalized 1st letter
Species
Always second
NOT capitalized
Both
Italicized or underlined
Base on Latin language
Apis mellifera

8. Scientific Names Conform to rules established No two the same
Gives biologist common way of communicating
Common names have problems
Ex: Robin
Different bird in US and England!

9. Classifying Organisms
Carl Linnaeus
Classification system
Ranked system of groups
Large groups subdivided into smaller groups
Increasingly similar
7 groups total
Now we have one more group
= Eight group levels

10. Classifying Organisms
Groups
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
Definition
Group of similar kingdoms
Group of similar phyla
Group of similar classes
Group of similar orders
Group of similar families
Group of similar genera
Group of similar species

11. Classifying Organisms
Groups
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
Danish Kings Play Chess On Fine Green Silk
Biggest
Smallest
Diverse
Similar

12. Identifying Organisms
Field Guides Use:
Image
Description
General info
Range
Common name
Scientific name

13. Identifying Organisms
Dichotomous Keys Use:
Pairs of descriptions
OR a question that can be answered in ONLY 2 ways
Read both descriptions or question
Choose one
Follow directions for next step
End up with a scientific name
Ex:
1a.   This organism has an exoskeleton    - go to number 2
1b.   This organism has an endoskeleton or no skeleton    - go to number 3

14. Identifying Organisms
Species
Unique
Differences in appearance and structure
Ex: Paramecium syngens
Once thought to be a single species
Look similar, but other differences

15. Species Biological species Defined by 1942 – Ernst Mayr:
A group of organisms that can reproduce only among themselves and are usually contained in a geographic region

16. Hybrids Hybrids Offspring produced by different species interbreeding
Reproductive barriers not complete
Some are fertile!
Ex: Dogs and wolves
Dogs = Canis familiaris
Wolves = Canis lupus

17. Biological Species Concept
Reproduction:
Most of kingdom Animalia = limited
Strong barriers
“Species only” fails in:
Organisms that reproduce asexually
Ex: prokaryotes
Transfer genes outside of reproduction
Still working on how to classify them

18. 17.2 Classification of Species
Put into groups based on similarities and differences
More similar = closely related
Suspect common ancestor

19. Classification of Species
Similarity of structure can be misleading
Not all characteristics inherited by offspring
Ex: Wings
Both birds and insects have . . .

20. Phylogeny
Evolutionary history for a group of species

21. Looking at Structures Convergent evolution Analogous characters
Converge = Come together
When similarities develop in organisms not closely related b/c
Live in similar habitats thus have similar adaptations
Analogous characters
Arise through convergent evolution

22. Characters in Groups Ancestral character
Feature in common ancestor of both groups
Ex:
Backbone
Birds and mammals

23. Characters in Groups Derived character
Found in only some members of a group
More shared = more closely related
Ex: Feathers
Birds but Not mammals

24. Cladistics Classification based on common ancestry
Clade - group of species that shares a common ancestor

25. Cladogram Cladogram Branching diagram
Shows hypothesized evolutionary relationships
Tips represent groups of descendent taxa
Nodes represent common ancestors

26. Cladistics
Outgroup – shares no derived characters with other groups being studied

27. Cladogram Shared derived character Shared ancestral characters
Evidence that groups are closely related
Ex: mammary glands
Shared ancestral characters
Not evidence groups are closely related
Ex: Limbs
Classification 12 min

28. Cladograms Strengths Weakness Objectivity
Either character exists or doesn’t
Weakness
Each character treated the same
Character impact or importance ignored

29. Phylogenetic Tree Taxonomist assign importance to characters
Branching tree-like diagram
Shows evolutionary relationships
inferred

30. Molecular Evidence Uses DNA to show relationships
Often considered the “last word” by scientists
Usually agrees with classification that was based on physical appearances
Reclassification sometimes necessary

31. 17.3 Molecular Clocks
Models that use mutation rates to estimate evolutionary time
Hypothesized that changes in DNA “add up”
Rate of mutations = “ticking” of time
More mutations = less closely related

32. Mitochondrial DNA mtDNA Found only in mitochondria
Only inherited from mother
Sperm loses mitochondria after fertilization
Mutation rate ~10x faster than nuclear DNA
Often used as molecular clock
Help classify closely related organisms

33. Ribosomal RNA
rRNA
Useful when comparing different species that may be very distantly related
Lots of time has passed
Lower mutation rate
Was used to reclassify Archaea and Bacteria into different domains

34. 17.4 Domains and Kingdoms Domain Recent classification group
Largest, broadest group
Recent classification group
1977, Carl Woese
American
Prokaryotes differ fundamentally in rRNA

36. Domain Bacteria Contains kingdom Bacteria Unicellular prokaryotes
Contains autotrophs and heterotrophs
Classified by:
Shape
Need for oxygen
Whether the cause disease

37. Domain Archaea Contain kingdom Archaea Unicellular prokaryotes
Some autotrophic, some heterotrophic

38. Domain Archaea Cell walls do NOT contain peptidoglycan
Live in “extreme” environments
Salt lakes
Antarctic waters
Deep sea vents
Hot geysers

39. Domains Archaea and Bacteria
No true “species”
Genes are shared outside of typical reproduction
Still trying to decide how to classify
Used to be classified together in one kingdom: Monera

40. Domain Eukarya Includes kingdoms: Eukaryotic cells
Protista
Plantae
Fungi
Animalia
Eukaryotic cells
Unicellular or multicellular

41. Review of Kingdoms
Bacteria
Archae
Protista
Fungi
Plantae
Animalia

42. Kingdom Bacteria Cell wall made of peptidoglycan
Web-like carbohydrate strands and peptide bridges

43. Kingdom Archaea Cell wall Cell membrane No peptidoglycan
Different lipids than bacteria or eukaryotes

44. Kingdom Protista Many unicellular Some have cell walls
Heterotrophs or autotrophs
Many move
Most reproduce asexually

45. Kingdom Fungi Most multicellular Cell walls contain chitin
Except yeasts
Cell walls contain chitin
Tough carbohydrate
Heterotrophic

46. Kingdom Plantae Multicellular Cell walls Eukaryotic Autotrophic
Cellulose (complex carb)
Eukaryotic
Autotrophic

47. Kingdom Animalia Multicellular Heterotrophs Eukaryotic
Mostly diploid cells
No cell wall
Organized cells
Motility