1. Classification

2. Why Classify?
To study the diversity of life, biologists use a classification system to name organisms and group them in a logical manner.
In taxonomy, scientists classify organisms and assign each organism a universally accepted name.
By using a scientific name, biologists can be certain that everyone is discussing the same organism.

3. Aristotle 384 BC
Classified organisms as either plants or animals

4. Carolus Linnaeus 1707-1778 Classification system
Based on physical structure
Taxonomic groups of related organisms
Binomial nomenclature (two names ex.Homo sapiens)

5. Binomial Nomenclature
 Carolus Linnaeus
In binomial nomenclature, each species is assigned a two-part scientific name.
The scientific name is always written in italics or underlined.
The first word (the genus) is capitalized
The second word (the species) is lowercased.
EX- Genus species or Genus species
Humans- Homo sapien

6. Linnaeus's System of Classification
A group or level of organization is called a taxonomic category, or taxon
Linnaeus had 7-
Kingdom “King
Phylum Phillip
Class Came
Order Over
Family For
Genus Great
Species Spaghetti”

7. Taxonomic Groups

9. Classification of Man Kingdom Animalia Phylum Chordata Class Mammalia
Order Primates
Family Hominidae
Genus Homo
Species Homo sapiens

10. Species
“Species are groups of actually or potentially interbreeding populations, which are reproductively isolated from other such groups.”
Reproductively isolated group
Ernst Mayr

11. Different Species

12. Checkpoint Questions:
1.  How are living things organized for study?
2. Describe the system for naming species that Linnaeus developed.
3. What are the seven taxonomic categories of Linnaeus’s classification system?
4. Why do scientists avoid using common names when discussing organisms?
5.  What is significant about members of the same species?

13. Modern Evolutionary Classification
Organisms are grouped into categories that represent lines of evolutionary descent, not just physical similarities
Modern classification systems are based upon biochemical and genetic evidence that indicates evolutionary relationships

14. Classification Using Cladograms
Cladistic analysis identifies and considers only the characteristics that arise as lineages evolve over time.
Characteristics that appear in recent parts of a lineage but not in its older members are called derived characters.
Derived characters can be used to construct a cladogram, a diagram that shows the evolutionary relationships among a group of organisms.

15. Cladogram Evolutionary relationship of a group of organisms
Each clad (group) share something in common
Ancestral traits are the oldest
Derived traits evolved later

16. Cladogram for Transportation
Wheels are the most ancestral
Wings are the most derived

17. Construct a Cladogram

18. Gorilla
Four limbs
Fur
Lost tail

19. Tiger
Four limbs
Fur
Tail

20. Lizard
Four limbs
Tail

21. Fish
Tail

22. Chimpanzee
Four limbs
Fur
Lost tail

23. Clad With 4 Limbs

24. Clad With Fur

25. Clad With No Tail

26. Characteristics for Constructing Cladogram
Tail is the most ancestral
Four limbs is the oldest derived trait
Fur is a later derived trait
Loss of tail is the most derived trait

27. Gorilla
Chimpanzee
Tiger
Lizard
Fish
Tail Lost
Fur
Four Limbs

28. Gorilla Tail?
How do we know the gorilla lost its tail?

29. Gorilla’s Vestigial Tail
Human
Gorilla

30. Traditional Classification Versus Cladogram TRADITIONAL CLASSIFICATION
Section 18-2
Appendages
Conical Shells
Crustaceans
Gastropod
Crab
Barnacle
Limpet
Crab
Barnacle
Limpet
Molted exoskeleton
Segmentation
Tiny free-swimming larva
TRADITIONAL CLASSIFICATION
CLADOGRAM
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31. Modern Evolutionary Classification
Similarities in DNA and RNA
The genes of many organisms show important similarities at the molecular level that can be used as criteria to help determine classification.

32. Modern Evolutionary Classification
Comparison reveals more DNA in common, the more recent the common ancestor
Molecular Clocks
A model known as a molecular clock uses DNA comparisons to estimate the length of time that two species have been evolving independently.

33. Terminology Classification Taxonomy Systematics Phylogeny
Assigning organisms to different catagories based on their relationship
Taxonomy
The science of naming organisms
Systematics
Determining evolutionary relationships of organisms
Phylogeny
Evolutionary history

34. Phylogenetic Tree Shows evolutionary relationships
More historical than cladogram

35. Echinodermata Uniramia Chelicerata Chordata Crustacea Protochordates
Lophophorates
Crustacea
Protochordates
Arthropoda
Annelida
Hemichordata
Mollusca
Other
pseudocoelomates
Nemertea
Platyhelminthes
Nematoda
Ctenophora
Cnidaria
Mesozoa
Placozoa
Sarcomastigophora
Ciliophora
Porifera
Apicomplexa
Microspora
Myxozoa

36. Birds
Mammals
Reptile
Amphibian
Fish
Four Limbs
Amniotic Egg
Endothermic
Fur
Feathers
Vertebrae

37. Monophyletic A group of all the descendants of a common ancestor
The common ancestor is in the group
Example: Mammalia
Ancestor was a mammal like reptile

38. Paraphyletic A group of descendants of a common ancestor
Common ancestor is in the group
Not all descendants are included
Example: Reptiles
Does not include birds and mammals

39. Polyphyletic A group that has some similarities
Common ancestor is in not in the group
Not all descendants are included
Example: Flying vertebrates

40. *
* Archaea

41. Checkpoint Questions:
How is information about evolutionary relationships useful in classification?
How are genes used to help scientists classify organisms?
3. What is the principle behind cladistic analysis?
4. Describe the relationship between evolutionary time and the similarity of genes in two species.
5. How have new discoveries in molecular biology affected the way in which we classify organisms compared with the system used by Linnaeus?