; Prokaryotes Prokaryotes
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Prokaryotes Prokaryotes

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									Prokaryotes

  They’re almost everywhere
Prokaryotes were the first
organism and persist today
as the most numerous and
pervasive of all living things.
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).
Diverse Adaptations of
Form and Function
Prokaryotes are generally single
celled organisms, although some
occur as aggregates, colonies, or
simple multi-cellular forms.
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.
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.
    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.
Domain           Domain            Domain
Bacteria         Archaea           Eukarya
(Eubacteria)   (Archaebacteria)   (Eukaryotes)




               Universal
               ancestor
    A Comparison of the Three
    Domains of Life
                                 Domain
Charactaristic     Bacteria     Archaea       Eukarya
Nuclear            Absent        Absent       Present
Envelope
Membrabce-         Absent        Absent       Present
enclosed
organelles
Peptidoglycan      Present       Absent       Absent
in cell wall
Membrane          Unbranched Some branced Unbranched
lipids           hydrocarbons hybrocarbons hybrocarbons
Characteristic      Bacteria        Archaea      Eukarya
RNA                 One kind     Several Kinds Several kinds
polymerase
Initiator amino      Formyl-      Methionine    Methionine
acid for start    methionine
of protein
synthesis
Introns              Absent        Present in    Present
(noncoding                        some genes
parts of genes)
Antibiotic      Growth inhibites Not inhibited Not inhibited
sensitivity     by streptomycin     by these     by these
                and                antibiotics  antibiotics
               chloramphenicol
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.
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.
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.
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.
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.
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.
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.
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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