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Prokaryotes

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Archaea and Bacteria are the two main branches of prokaryotic evolution. ... VARIATION. Genetic variation occurs in prokaryotes through mutation and gene transfer. ... – PowerPoint PPT presentation

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Title: Prokaryotes


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Prokaryotes
  • Theyre almost everywhere

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Prokaryotes were the first organism and persist
today as the most numerous and pervasive of all
living things.
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Archaea and Bacteria are the two main branches of
prokaryotic evolution. Prokaryotes account for
two of three domains (super kingdoms) of
life. Molecular systematics suggests that
archaebacteria (domain Archaea) may be more
closely related to eukaryotes (domain Eukarya)
than to eubacteria (domain Bacteria).
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Diverse Adaptations of Form and Function
Prokaryotes are generally single celled
organisms, although some occur as aggregates,
colonies, or simple multi-cellular forms.
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Diverse Adaptations of Form and Function
Prokaryotes are generally single celled
organisms, although some occur as aggregates,
colonies, or simple multi-cellular forms. The
three most common prokaryotic shapes are
spherical (cocci) , rod shaped (bacilli), and
helical forms.
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Diverse Adaptations of Form and Function
Prokaryotes are generally single celled
organisms, although some occur as aggregates,
colonies, or simple multi-cellular forms. The
three most common prokaryotic shapes are
spherical (cocci) , rod shaped (bacilli), and
helical forms. Nearly all prokaryotes have
external cell walls, which protect and shape the
cell and prevent osmotic bursting. Cell walls of
eubacteria typically contain the polymer
peptidoglycan. Gram-positive and gram-negative
bacteria differ in the structure of their walls
and other surface layers.
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ADAPTATIONS
  • Many species secrete sticky substances that form
    capsules. Some have surface appendages called
    pili outside the cell wall. Both structures help
    the cells adhere to one another, and some pili
    are specialized for conjugation.
  • Motile bacteria propel themselves by flagella,
    use flagella-like filaments positioned inside the
    cell wall (spirochetes) or glide on slime
    secretions.
  • Prokaryotic cells are not compartmentalized by
    endomembranes. However, invaginations of the
    plasma membrane may provide internal membrane
    surface for specialized functions.

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Domain Archaea(Archaebacteria)
Domain Bacteria(Eubacteria)
Domain Eukarya (Eukaryotes)
Universal ancestor
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A Comparison of the Three Domains of Life
Domain
Charactaristic Bacteria Archaea Eukarya
Nuclear Envelope Absent Absent Present
Membrabce-enclosed organelles Absent Absent Present
Peptidoglycan in cell wall Present Absent Absent
Membrane lipids Unbranched hydrocarbons Some branced hybrocarbons Unbranched hybrocarbons
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Characteristic Bacteria Archaea Eukarya
RNA polymerase One kind Several Kinds Several kinds
Initiator amino acid for start of protein synthesis Formyl-methionine Methionine Methionine
Introns (noncoding parts of genes) Absent Present in some genes Present
Antibiotic sensitivity Growth inhibites by streptomycin and chloramphenicol Not inhibited by these antibiotics Not inhibited by these antibiotics
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DNA
  • The prokaryotic genome consists of a single
    circular DNA molecule in a nucleoid region
    unbounded by a membrane.
  • Many species also possess smaller separate rings
    of DNA called plasmids, which code for special
    metabolic pathways and resistance to antibiotics.

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REPRODUCTION
  • Bacteria reproduce asexually.
  • The type of cell division by which these
    prokaryotes reproduce is called binary fission.
  • During binary fission, each dividing daughter
    cell receives a copy of the single parental
    chromosome.

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VARIATION
  • Genetic variation occurs in prokaryotes through
    mutation and gene transfer.
  • All major types of nutrition and metabolism
    evolved among prokaryotes.
  • The evolution of prokaryotic metabolism was both
    cause and effect of changing environments on
    Earth.

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IMPACT TODAY
  • Prokaryotes continue to have an enormous
    ecological impact.
  • Prokaryotes, along with fungi, are decomposers
    that recycle chemical elements in ecosystems.
  • Some prokaryotes live with other species in
    symbiotic relationships.

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PROKARYOTES TODAY
  • Some parasitic prokaryotes are pathogenic,
    causing disease in the host.
  • Bacteria have been put to work in laboratories,
    sewage treatment plants, and the food and drug
    industry.

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EUKARYOTES
  • Eukaryotes originated by symbiosis among
    prokaryotes.
  • The first eukaryotes to evolve from prokaryotic
    ancestors were probably unicellular.
  • The primal eukaryotes were ancestral to plants,
    fungi, and animals, the eukaryotic organisms most
    familiar to us.

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PROCESS I
  • INVAGINATION OF THE PLASMA MEMBRANE.
  • The nuclear envelope, endoplasmic reticulum,
    Golgi apparatus, and related structures, may have
    evolved from specialized invaginations
    (infoldings) of the prokaryotic plasma membrane.

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PROCESS II
  • ENDOSYMBIOSIS-Dr. Lynn Margulis of the University
    of Massachusetts
  • Eukaryotic cell arose as a result of prokaryotes
    taking up residence inside other prokaryotes.
  • The term endosymbiont is used for a cell that
    lives within another cell, termed the host cell.
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