Classifying Living Things

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Classifying Living Things
Taxonomy- discipline of classifying organisms and
assigning each organism a universally accepted
name
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18-1 Finding Order in Diversity

• Why do we classify?
• Help to study the diversity of life (makes orgs
  easier to identify and compare)
• Groups organisms in a logical manner
• Organisms in the same group will be more like
  each other

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Timeline of Classification

• 1. 384 322 B.C. Aristotle
• 2 Kingdom Broad Classification
• 2. 1735 - Carl Linnaeus
• 2 Kingdom Multi-divisional Classification
• Kingdom, Phylum, Class, Order, Family Genus,
  Species
• 3. Evolutionary Classification (After Darwin)
• Group By lines of Evolutionary Descent
• 4. 5 Kingdom System 1950s
• 5. 6 Kingdom System 1990s
• 6. 3 Domain System 1990s

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Early Classification Aristotle 384-322 B.C.

• 2 Groups Plants and Animals
• Plants Green, Non Mobile
• Further classified based on size and pattern of
  growth
• Tree, Herb, Shrub
• Animals Not Green, Mobile
• Further classified based on where organism lives
• Water, Air, Land

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How would you classify this using the
Plant/Animal system?
Praying Mantis Green but.. Mobile
Aristotles Grouping of life not specific enough
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Carl Linnaeus

• (1735) Swedish Botanist
• Reworked Classification system
• Based on Comparative Morphology
• Called his classification Systema Naturae
• Used a hierarchy of categories to classify
• Compared physical traits of Organisms
• Used Comparative Morphology

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Changes Linnaeus Made to Aristotles System

• Both had 2 Kingdom Systems
• Plantae and Animalia
• Differences
• 1. Plants and Animals were classified using more
  divisions - to account for diversity
• 2. Each division from Kingdom to species is based
  on specific traits
• Ex Vertebrae, Mammary Glands, Diet
• 3. Taxons of each group are descriptive of trait
  being used in forming that group
• Ex Class Mammalia mammary glands are used to
  nurse young

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Challenges of Classification

• 1. Many different kinds of living things
• Today we have identified and named 1.5 million
  species
• Millions more are believed to be unclassified
• Organisms scattered all over the world, some in
  harsh, difficult to reach environments
• 2. Classifications are made by people
• Opinions may differ from scientist to scientist

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Linnaeus Divisions Still Used in Modern
Classification

• 1. Kingdom largest group
• 2. Phylum
• 3. Class
• 4. Order
• 5. Family
• 6. Genus
• 7. Species
• (Most Closely Related)

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Linnaeus System of Classification
Largest (top) to smallest (bottom) King Phil Came
Over For Good Spaghetti
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Mnemonic Device To help remember categories and
order

• Kingdom - King
• Phylum - Phillip
• Class Came
• Order Over
• Family - For
• Genus - Ginger
• Species - Snaps

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Linnaeus Introduced Scientific Naming

• Binomial Nomenclature is the 2 word scientific
  name of an organism
• Uses Genus and Species
• Genus is capitalized, not species, all italicized
• In writing the name, cant italicize, so
  underline
• Homo sapien (Genus and species of Human)
• Panthera leo (Genus and species of Lion)
• Used Latin Universal unifying, dead language
• Latin can be understood by all scientists,
  regardless of native language
• Uniform, unlike common name usage
• Ex Cougar, Puma, Panther- all same organism
• name depends upon where you live, but Scientific
  same
• Felis concolor

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Naming Organisms

• Binomial Nomenclature
• Developed by Carolus Linnaeus
• Each species assigned a 2 part scientific name
• Genus species (italics with the genus
  capitalized)
• Armadillidium vulgare

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Carolus Linnaeus
Genus
Species
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What is the genus and species of each of these
animals

• Common name  Scientific name 
• 1. Domestic dog  Canis familiaris 
• 2. Puma  Puma concolor 
• 3. Jaguar  Panthera onca 
• 4. Lion  Panthera leo 
• 5. Leopard  Panthera pardus

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Linnaeus Classification Cont.

• Species shows most closely related orgs. in
  system, but still may show variation
• Ex All common dog breeds are in the same species
  (Canis familiaris)
• Basic Unit of Evolution is the Species
• Speciation is continuous, so Taxonomists have to
  keep naming new species
• Reproductive Barriers try to keep species
  separate
• Does not always work Hybrids
• Donkey and Horse make a sterile Mule

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Tools Used to Classify Organisms

• 1. Comparative Morphology
• Compares Physical Structures, Traits
• 2. Evolutionary Relationships
• Related Organisms with common ancestors, Derived
  Characters
• 3. DNA/RNA comparison

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Cladistics Determines Evolutionary Classification

• Evolutionary Classification compares Homologous
  Structures as well as Genetics
• Homologous Structures Structures with different
  functions but similar development patterns
• -Divergent Evolution organisms that have a
  common ancestor
• Derived Character new trait which appears in
  more recent (newer) organisms not seen in the
  ancestor organism
• Derived Characters are distinguishing traits
  between organisms in an evolutionary
  classification
• See Overhead of plant adaptations

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Cladistic Analysis for Evolutionary Classificaiton

• Cladistic analysis identifies and considers only
  those characteristics of organisms that are
  evolutionary innovations.
• Derived Characteristics- characteristic that
  appears in recent parts of a lineage, but not in
  its older members
• Cladogram- diagram that shows the evolutionary
  relationships among a group of organisms

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Evolutionary Classification

• Groups represent lines of Evolutionary Descent
• Not simply based on simply on Morphology
• Ex Even though they have similar Morphology,
  Dolphins and Sharks are not closely related
• Sharks and Dolphins developed Analogous
  Structures
• due to similar environments
• not common ancestry or common development
• Traits, DNA and RNA analysis used to determine
  relation
• Determines Common Ancestry more basic form of
  life from which new species came

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Linnaeus System Evolves from 2 Kingdoms to 6

• As we learned more about different kinds of life,
  there needed to be more Kingdoms
• 1800s Added Kingdom Protista
• Amoeba, Slime Molds
• 1950s Added Fungi and Monera
• Fungi distinguished from Plants
• Prokaryotes (no nucleus) Bacteria given category
• 1970s Split Kingdom Monera into 2 separate
  Kingdoms
• Eubacteria bacteria with peptidoglycan
• Archaebacteria bacteria without peptidoglycan

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6 Kingdom System
Animalia Plantae Fungi Protista Eubacteria Archaea
bacteria
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Other Ways to Help Determine Evolutionary time
for Classification

• Similarities in DNA and RNA
• Similar DNA molecules help determine
  classification
• How close species are related
• Molecular Clocks
• Molecular clock- uses DNA comparisons to estimate
  length of time two species have been evolving
  independantly

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Three Domain System

• 1990s
• Domain is larger classification than Kingdom
• Used Technology to compare Ribosomal RNA
  sequences of organisms
• Determined how long organisms had been evolving
  independently
• Shows Evolutionary Relationships
• Uses molecular clock to determine how long
  ago orgs were related
• Based on how many sequences are different ( of
  mutations, order of mutations)

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4. Three Domain System

• 1. Domain Bacteria
• Corresponds to Eubacteria Kingdom
• Unicellular Prokaryotic Organisms
• No Nucleus
• Ecologically Diverse live everywhere!
• Metabolically Diverse
• Cell Walls contain substance called Peptidoglycan
  special protein and sugar
• Trait used to distinguish between
• Bacteria and Archaea
• Target of many Antibiotics

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Three Domain System

• 2. Domain Archaea Ancient Bacteria
• Corresponds to Kingdom Archaeabacteria
• Unicellular, Prokaryotes
• Metabolically Diverse
• No nucleus
• Live in Extreme environments like those of early
  Earth
• Cell walls without Peptidoglycan
• A trait used to distinguish between Archaea and
  Bacteria Domains

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Three Domain System

• 3. Eukarya
• Contains Kingdoms
• Protista, Fungi, Plantae, Animalia
• Eukaryotic, single or multi-cellular organisms
• All orgs in this domain have a Nucleus
• Most visible life is in this domain

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Classification Key

• Also Known as
• Dichotomous Key, Biological Key
• Useful in Identifying Organisms
• Based on Comparison of Morphological Traits
• Use physical features to compare, contrast
• Determine if Organism is in group or not, based
  on Key criteria
• At each level you only have a few contrasting
  characteristics to choose from (if have, if not
  have)
• Ex Tennis shoe, non Tennis shoe
• Body shape plans, Characteristics such as fur
• Refer to your Shark Lab Hand Out