Chapter 18 Classification

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Chapter 18 Classification
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Why Classify??

• Human nature- we love to put things in their
  place!
• Organization
• Identification
• Less Confusion
• Show Relationships

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Taxonomy

• The branch of biology that names and groups
  organisms according to their characteristics and
  evolutionary history.
• Classify the thousands of new species discovered
  each year.
• 1. 5 million so far
• ?? millions yet to be discovered.

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• Biologists use the characteristics of newly
  discovered species to classify it with organisms
  having similar characteristics.
• The way we group organisms today continues to
  change and reflect the evolutionary history of
  organisms.

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Early Systems of Classification

• Aristotle
• Linnaeus

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Aristotle

• Greek Philosopher 384-322 BC
• First classified organisms more than 2000yrs ago
  as either plants or animals.
• Animals land dwellers, water dwellers, or air
  dwellers.
• Plants three categories based on differences in
  their stems.

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Aristotle
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Carolus Linnaeus

• Father of Taxonomy
• Swedish naturalist
• 1707-1778
• 100 years before Darwin!

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• 1735 published Systema Naturae.
• Devised a system of grouping organisms into
  hierarchical categories.
• Used an organisms morphology (form and
  structure) its appearance

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1707-1778
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Levels of Classification

• Kingdom
• Phylum or Division
• Class
• Order
• Family
• Genus
• Species

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King Philip Came Over For Gold Specks
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• Under the modern Linnaean system, the
  classification of an organism places the organism
  within a nested hierarchy of taxa. (taxon
  singular)

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Binomial Nomenclature

• Scientific Name has two parts.
• 1st part is the genus
• 2nd part is the species which is the identifier
  or descriptive word.
• Genus name is capitalized and both names are
  underlined or written in italics.

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• Latin used by all scientists as a standard.
• Linnaeus classified 1000s of organisms.
• Versions of his system are still used today.

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Scientific Names

• May describe the organism, suggest geographic
  range, or honor a person
• Homo sapiens (homo man sapiens wise)
• Chaos chaos (amoeba never appear the same shape)

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Linnaea borealis (Linnaeus favorite, borealis
northern)
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• Lupinus texensis
• Texas bluebonnet

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Phylogeny

• Phylogeny is evolutionary history
• Much of Linnaeus work in classification is
  relevant even in the context of phylogeny because
  morphological features are largely influenced by
  genes and are clues of common ancestry.

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Evolutionary Classification

• Biologists now group organisms into categories
  that represent lines of evolutionary descent, or
  phylogeny, not just physical similarities
• Phylogeny the study of evolutionary
  relationships

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Modern taxonomic placement involves

• Morphology
• Chromosomal characteristics
• Nucleotide and amino acid sequences (chromosomes)
• Embryological development
• Information from the fossil record.

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Phylogenetic tree

• Family tree that shows the evolutionary
  relationships thought to exist among groups of
  organisms.
• Represents a hypothesis and is based on several
  lines of evidence.
• Subject to change as new information arises.

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Phylogenetic Tree
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Interpreting a Phylogenetic Tree

• Organism at base of tree is common ancestor to
  all the others in the tree.
• Branch points indicate the evolution of some
  characteristic that splits a group into two
  groups.
• Groups shown at tips of branches include
  organisms that have evolved most recently.

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Molecular Clocks

• This model uses comparisons of DNA, RNA and
  proteins to estimate the length of time that two
  species have been evolving independently.
• The degree of dissimilarity is, in turn and
  indication of how long ago the two species shared
  a common ancestor.

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DNA comparisons (Artic bluegrass)
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DNA banding patterns
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Cladistics

• Relatively new system of phylogenetic
  classification.
• Uses certain features of organisms called shared
  derived characteristics to establish evolutionary
  relationships.

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• Derived character feature that apparently
  evolved only within the group under
  consideration. Example feathers in birds are
  inherited from a common ancestor.

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To interpret a cladogram

• Begin at the bottom and move up the axis that
  shows branch points.
• Groups and derived characteristics appeared in
  the order shown.
• Example all groups branching above lungs have
  lungs. Those below do not.

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Cladogram
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Two Modern Systems of Classification

• Six Kingdom System
• Three Domain System

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Six Kingdom System

• Kingdom Archaebacteria
• Kingdom Eubacteria
• Kingdom Protists
• Kingdom Fungi
• Kingdom Plantae
• Kingdom Animalia

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Six Kingdoms
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Kingdom Archaebacteria
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Kingdom Archeabacteria

• Prokaryotic
• Unicellular
• Cell walls (without peptidoglycan)
• Autotroph or heterotroph

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Kingdom Archaebacteria

• Some autotrophic produce food by chemosynthesis
  and methane waste.
• archae ancient
• May be directly descended from and very similar
  to first organisms on Earth

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• Can withstand extreme conditions
• Thermophiles (heat)
• Halophiles (salt)
• Methanogens (methane gas)
• Many live in harsh environments sulfurous hot
  springs, salty lakes, anaerobic environments,
  intestines of animals.

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Kingdom Eubacteria
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Kingdom Eubacteria

• eu true
• Prokaryotic
• Unicellular
• Cell walls (with peptidoglycan)
• Autotroph or heterotroph

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• Bacteria that affect your life tooth decay, turn
  milk to yogurt, food poisoning, illness
• Most use oxygen, but a few cannot live in O2
• Both Eubacteria and archaebacteria make up the
  greatest number of living things on Earth.

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• Eubacteria and archaebacteria reproduce by binary
  fission but do have methods of genetic
  recombination to allow evolution to occur.
• Short generation times (30 minutes) allow rapid
  evolutionary response to environmental change.
  Example antibiotic resistant bacterial infection.

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Kingdom Protista
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Kingdom Protista

• Eukaryotic
• Cell walls of cellulose
• Mostly single-celled organisms, but some
  multicellular but lack specialized tissues
• Autotrophic and heterotrophic
• Include Protozoa and Algae

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• Many species distantly related.
• Broad kingdom contains all eukaryotes that are
  not plants, animals, or fungi. 50,000 species.
• Sexual cycles of many are unknown but thought to
  have some process of genetic recombination.

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Kingdom Fungi
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Kingdom Fungi

• Unicellular and multicellular
• Eukaryotic
• Cell walls of chitin
• Heterotrophic
• Absorb nutrients rather than ingesting
• 100,000 species mushrooms, yeast, mildews, and
  molds.

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• Sexual cycles not known for many fungi. It is
  likely that all species have some way of
  promoting genetic recombination.

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Kingdom Plantae
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Kingdom Plantae

• Multicellular plants
• All except for a few parasitic forms are
  autotrophic and use photosynthesis as a source of
  energy
• Eukaryotic
• Most live on land
• Sessile dont move around

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• Most have a sexual cycle based on meiosis
• 350,000 species identified including mosses,
  ferns, conifers, flowering plants.

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Kingdom Animalia
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Kingdom Animalia

• Eukaryotic Heterotrophs
• Multicellular No cell walls
• Most have symmetrical body organization
• Move about their environment
• Have a sexual cycle based on meiosis
• About 1,000,000 species

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Three Domain System

• Molecular biology has led to an alternative to
  the 6 kingdom system
• Comparing sequences of ribosomal RNA in many
  organisms. Estimated how long ago pairs of
  organisms shared a common ancestor.

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• Phylogenetic tree drawn from this data shows that
  living things seem to fall naturally into 3 broad
  groups or domains.

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The Three Domains (and the kingdoms they include)

• Bacteria (Eubacteria)
• Archaea (Archaebacteria)
• Eukarya (Eukaryotes) includes Protista, Fungi,
  Plantae, Animalia

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Three Domains
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Three Domains
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Conclusions from the Three Domain System

• All eukaryotes have true nuclei with linear
  chromosomes and membrane-bound organelles.
• The most variation in Eukarya is among protists.

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• When considered from the perspective of the
  complete diversity of life on Earth, the fungi,
  plants, and animals are quite similar to each
  other.