1. Biological
Classification
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2. Nature’s Need for Organization
Lots of diversity!
5,200 Prokaryotes
100,000 Fungi
290,000 Plants
52,000 Vertebrates
1,000,000 Insects
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3. Biological Classification
Classification: grouping objects or information by similarities.
Taxonomy: branch of biology that names and classifies species & then combines them into even broader groups.
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4. Classifying Life
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5. Classification History
1st biological classification system: Greek philosopher Aristotle.
Aristotle’s system was replaced by Linnaeus’s System.
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6. Linnaeus’ System
Carolus Linnaeus - Swedish botanist who developed a classification system based on physical and structural similarities of organisms.
He also developed the two- word naming system called Binomial Nomenclature.
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7. Binomial Nomenclature
A naming system that involves a Genus and a Species name.
Genus: first word of the naming system.
A group of similar species.
Species: second word of the naming system.
This describes a characteristic of the organism.
Example: Scientific name for humans is Homo sapiens
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8. What is a Species?
A species is a unique group of organisms that are able to interbreed with each other to produce fertile offspring and that usually do not reproduce with members of any other group.
Example: The horse and zebra belong to two different species. Although they can mate, their offspring (Zebroid) are sterile.

9. Why Latin?
It was used in the middle ages when scientists first began to name organisms.
Latin is the universal language of classification.
This language is one of the most stagnant (unchanging) and stable language that is available.
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10. Taxonomic Ranks Domain Kingdom Phylum (or Division for plants) Class
Order
Family
Genus
Species
(Dorky Kings Play Chess on Fat Green Stools)
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11. Taxonomic Ranking Continued
Similar species are combined into a genus
Similar genera are united into a family
Similar orders are collected into a class
Similar classes are united into a phylum
Similar phyla are collected into a kingdom
Similar kingdoms are grouped into a domain.
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12. Classifying Life
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13. Biology’s Three Domains
Bacteria, Archae, Eukarya
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14. How Do We Classify Organisms?
When placing an organism into a group taxonomists consider its:
• Morphology (appearances & behaviors)
• Chromosomal Characteristics (traits)
• DNA/RNA & Amino Acid Sequences (genes)
• Embryological Development (life-cycles)
• Fossil Records (past histories)
All of the above are used to yield reliable information about the evolutionary history of an organism.

15. Evolutionary History Phylogeny - an organism’s evolutionary history
Convergent evolution produces analagous structures
Divergent evolution produces homologus structures
Most biologists today analyze evolutionary relationships using Cladistics
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16. How Do We Classify Organisms?
1) Cladistics (Cladograms) – a new system that uses certain features of organisms called, shared derived characteristics, to show relationships.
Derived character - character that evolved in an ancestor of one group, but not the other
Example: feathers evolved in birds, but not mammals

17. Cladistics
Shared derived characters provide evidence that two groups are relatively closely related
Example: Mammary glands, when looking at lizards, dogs, and whales
Cladogram: Branching models showing phylogeny of species.
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18. Cladogram
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19. How Do We Classify Organisms?
2) Evolutionary Systematics (Phylogenetic Trees) – show relationships thought to exist among groups of organisms.
Gives varying degrees of importance to characters, thus producing a subjective analysis of evolutionary relationship
Phylogenetic Tree - branching diagram that shows evolutionary relationships based on characters AND the bias of those that created it.

20. Cladogram vs. Phylogenetic Tree
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21. Identifying Organisms
Scientists construct/use keys
Dichotomous keys - keys with two choices at each step
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