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Classifying Living Things


... mammary glands are used to nurse young. Challenges of Classification ... Body shape plans, Characteristics such as fur. Refer to your Shark Lab Hand Out ... – PowerPoint PPT presentation

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Title: Classifying Living Things

Classifying Living Things
Taxonomy- discipline of classifying organisms and
assigning each organism a universally accepted
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

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,
  • 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

Early Classification Aristotle 384-322 B.C.
  • 2 Groups Plants and Animals
  • Plants Green, Non Mobile
  • Further classified based on size and pattern of
  • Tree, Herb, Shrub
  • Animals Not Green, Mobile
  • Further classified based on where organism lives
  • Water, Air, Land

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

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

Challenges of Classification
  • 1. Many different kinds of living things
  • Today we have identified and named 1.5 million
  • 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

Linnaeus Divisions Still Used in Modern
  • 1. Kingdom largest group
  • 2. Phylum
  • 3. Class
  • 4. Order
  • 5. Family
  • 6. Genus
  • 7. Species
  • (Most Closely Related)

Linnaeus System of Classification
Largest (top) to smallest (bottom) King Phil Came
Over For Good Spaghetti
Mnemonic Device To help remember categories and
  • Kingdom - King
  • Phylum - Phillip
  • Class Came
  • Order Over
  • Family - For
  • Genus - Ginger
  • Species - Snaps

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
  • 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
  • Felis concolor

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

Carolus Linnaeus
What is the genus and species of each of these
  • 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

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
  • Does not always work Hybrids
  • Donkey and Horse make a sterile Mule

Tools Used to Classify Organisms
  • 1. Comparative Morphology
  • Compares Physical Structures, Traits
  • 2. Evolutionary Relationships
  • Related Organisms with common ancestors, Derived
  • 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
  • See Overhead of plant adaptations

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

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
  • due to similar environments
  • not common ancestry or common development
  • Traits, DNA and RNA analysis used to determine
  • Determines Common Ancestry more basic form of
    life from which new species came

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
  • Eubacteria bacteria with peptidoglycan
  • Archaebacteria bacteria without peptidoglycan

6 Kingdom System
Animalia Plantae Fungi Protista Eubacteria Archaea
Other Ways to Help Determine Evolutionary time
for Classification
  • Similarities in DNA and RNA
  • Similar DNA molecules help determine
  • How close species are related
  • Molecular Clocks
  • Molecular clock- uses DNA comparisons to estimate
    length of time two species have been evolving

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
  • 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)

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

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
  • Cell walls without Peptidoglycan
  • A trait used to distinguish between Archaea and
    Bacteria Domains

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

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
  • Ex Tennis shoe, non Tennis shoe
  • Body shape plans, Characteristics such as fur
  • Refer to your Shark Lab Hand Out