The Origins of Eukaryotic Diversity

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Chapter 28 The Origins of Eukaryotic Diversity
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I.  Introduction to the protists             A. 
Systematists split protists into many
kingdoms                         1.  In the five
kingdom system, anything that wasnt a
prokaryote, plant, animal, or fungus was grouped
as a protist.   2.  Systematists now divide
protists into as many as 20 separate
kingdoms.   Figure 28.2 (p. 547) The kingdom
Protista problem.
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            B.  Protists are the most diverse of
all eukaryotes                        
                        Figure 28.1 (p. 546)
Too diverse for one kingdom  a small sample of
protists.
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                         General Description of
Protists 1.  Very few general characteristics can
be cited without many exceptions.  2.  Most
protists are unicellular, but some are colonial
or even multicellular. - Many protist cells are
very complex à individual cell must perform all
the basic functions performed by specialized
cells of plants and animals.
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 3.  Nutrition - Protists may be autotrophic,
heterotrophic, or mixotrophic organisms. 
Mixotrophic organisms combine photosynthesis and
food ingestion a.  Photosynthetic  algae
(plant-like) b.  Ingestive  protozoa
(animal-like)                                    
c.  Absorptive  fungus-like              4. 
Motility  a.  Most protists are motile  they
have either flagella or cilia. ? Eukaryotic and
prokaryotic flagella are not homologous
structures.
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5.  Life Cycle a.  Some protists are asexual. 
b.  Some reproduce sexually by meiosis and then
go on to reproduce asexually. c.  Cysts form at
some point during the life cycle of many
protists.  Cysts are resistant cells that are
capable of surviving harsh conditions.   6. 
Habitat a.  Most protists are aquatic. b. 
Plankton are organisms that drift or swim near
the surface of the water ? Phytoplankton are
responsible for half of the worlds
photosynthesis and O2 production. The following
Figure (28.3) gives details for a common Protist
(Euglena) and should be a model for what you
remember of single-celled Protists
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• II.  Origin and early diversification of
  eukaryotes
•             A.  Endomembranes contributed to
  larger, more complex cells
•                        
• Endomembranes evolved from infoldings of
  prokaryotic membranes.
• Endomembranes allowed for compartmentalization
  of cellular functions. This contributed to the
  evolution of increasing complexity and
  development of new functions ? This is a great
  example of the development of emergent
  properties!
•  
• Figure 28.4 (p. 549) A model of the origin of
  eukaryotes.

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 B.  Mitochondria and chloroplasts evolved from
endosymbiotic bacteria                        
1.  Heterotrophic prokaryotes were engulfed and
function as mitochondria. 2.  Photosynthetic
prokaryotes were engulfed and function as
chloroplasts.   C.  Eukaryotic cell is a chimera
of prokaryotic ancestors ? The term chimera
refers to the mixture of three prokaryotes.       
                              a.  Original
contributes genome b.  One becomes
mitochondrion c.  One becomes chloroplast    Figur
e 28.5 (p. 551) Secondary endosymbiosis and the
origin of algal diversity. Note Chloroplast is
called a plastid
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2.  After the first eukaryotes formed, there was
a great wave of diversification.   Figure 28.8
(p. 554) A tentative phylogeny of eukaryotes.
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III.  Protistan diversity             A. 
Diplomonadida and Parabasala                      
   1.  Lack mitochondria                          
           - Examples of eukaryotes that evolved
without acquiring endosymbiotic heterotrophic
bacteria.  ? Most systematists think they lost
them.                           2.  Giardia
lamblia à example of Diplomonad  - Humans ingest
cysts by drinking feces-contaminated water.  -
Parasite absorbs body fluids from host (Huge
outbreaks occurred in Wisconsin and Pennsylvania
recently that required heavy chlorination of
water supplies.) Question Why doesnt Giardia
need mitochondria?    Figure 28.9 (p. 555)
Giardia lamblia, a diplomonad.
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3.  Trichomonas vaginalis à example of
Parabasalid                                     -
Parasite of the vagina.   Note  These
organisms live as parasites and they dont need
to have mitochondria and respire on their own.
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            B.  Euglenozoa                        
1.  Characterized by one or two flagella and
paramylon which is a glucose polymer. Example
Euglena!                           2.  Most
members of this group are photosynthetic
(autotrophs). However,                          
3.  Kinetoplastids (Trypanosoma) cause sleeping
sickness. Its symbiotic. By which type of
symbiosis does it live?    Figure 28.11 (p. 556)
Trypanosoma, the kinetoplastid that causes
sleeping sickness.
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•             C.  Alveolata
•                         1.  Characterized by
  small cavities under the cell surface (alveola).
•  
•                         2.  Dinoflagellate
  (phytoplankton) blooms cause red tide and
  produce toxins. Example
•                                    
•  

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• Pfisteria acts as a carnivore  kills fish,
  feeds on flesh.
• Others form the basis of many food chains in the
  oceans and function as photosynthetic plankton.
• Others are bioluminescent and produce light when
  disturbed to attract fish that eat predators that
  eat the Dinoflagellates.

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                        3.  Apicomplexa are
animal parasites      - e.g. Plasmodium causes
malaria.    Figure 28.13 (p. 557) The two-host
life history of Plasmodium, the apicomplexan that
causes malaria.
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                        4.  Ciliophora            
                         - Use cilia for
movement.                                     -
e.g. Stentor and paramecium. These ciliates have
one macronucleus and several micronuclei
                                      Figure
28.14 (p. 558) Ciliates.
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            D.  Stramenopila                      
   1.  Diverse group of heterotrophs and
phototrophs (algae)                               
      - Usually have hairy flagella Four taxa
are within the stramenopila   2.  Oomycota are
water molds primarily heterotrophs.    
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The remaining members of this taxon are called
Heterokont algae. They are photosynthetic and
contain endosymbiotic plastids (chloroplasts).
The taxa within the group are 3. 
Bacillariophyta (diatoms) have glass-like walls
and exist as phytoplankton.                       
              - e.g. Pinnularia                   
                    Figure 28.17 (p. 561)
Diatoms.
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 4.  Chrysophyta are golden algae that live in
colonies                                     -
e.g. Dinobryon   Figure 28.18 (p. 562) A
golden alga
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  5.  Phaeophyta are brown algae                  
                   - Kelp (seaweed) grow up to
60 meters per year and are harvested for
food.    Figure 28.20 (p. 563) A kelp forest.
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                        6.  Algal life
cycle                                     -
Alternation of generations                        
               Need to know this!!            
                           Figure 28.21 (p. 564)
The life cycle of Laminaria  an example of
alternation of generations.
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            E.  Rhodophyta (red
algae)                         1.  No
flagella                                     -
Porphyra                           Figure 23.22
(p. 565) Red algae.
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            F.  Chlorophyta (green
algae)                         1.  Characterized
by green chloroplasts, similar to those found in
plants.                                     Exist
as unicellular (Chlamydomonas), colonial (Volvox)
and multicellular (Caulerpa) organisms.    Figure
28.23 (p. 566) Colonial and multicellular
chlorophytes. These are the forerunners of early
plants? Colonies and multicellular chlorophyta
evolved to become the higher plants. Again, an
example of emergent properties.
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            G.  Some protists use pseudopodia for
movement and feeding. The examples that follow
are of uncertain phylogeny.                       
  1.   Pseudopodia are cellular extensions that
may bulge from almost anywhere on the
cell.                           2.  Typically
heterotrophs                           3.  Best
known examples are amoebas (Rhizopoda).           
                Figure 28.26 (p. 569) Use of
pseudopodia for feeding.
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            H.  Mycetozoa are slime
molds                         Know this life
cycle!!                           Figure 28.29
(p. 571) The life cycle of a plasmodial slime
mold, such as Physarum.  
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            Note  Table 28.1 (p. 573) is a
good place to begin memorizing clades and
features.
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