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					Kingdom Protista

     Protists
Even a low-power microscope
  –Can reveal an astonishing menagerie of
  organisms in a drop of pond water




                        50 m
    Protist Diversity

•Protists are more diverse than all other
eukaryotes
  –And are no longer classified in a single
  kingdom

•Most protists are unicellular
  –And some are colonial or multi-cellular
            Protist Diversity

• Organisms that range in size from
  single cells to complex structures
  more than 100 meters long.

• They show a variety of reproductive
  and nutritional strategies.
                  Protist Diversity

•Protists, the most nutritionally diverse of all
eukaryotes, include
  –Photoautotrophs, which contain chloroplasts

  –Heterotrophs, which absorb organic molecules
  or ingest larger food particles

  –Mixotrophs, which combine photosynthesis and
  heterotrophic nutrition
Protists are also diverse in habitat
     •Including freshwater and marine species
                                    (a) The freshwater ciliate Stentor,
                                        a unicellular protozoan (LM)




                                               100 m


                 100 m




                          (b) Ceratium tripos, a unicellular marine dinoflagellate (LM)
                  4 cm




                 (c) Delesseria sanguinea, a multicellular marine red alga


                 500 m




                  (d) Spirogyra, a filamentous freshwater green alga (inset LM)
                ProtistA Evolution

•There is now
considerable
evidence
  –That much of
  protist diversity
  has its origins in
  endosymbiosis
               ProtistA Evolution

•The plastid-bearing lineage of protists
  –Evolved into red algae and green algae

•On several occasions during eukaryotic
evolution
  –Red algae and green algae underwent
  secondary endosymbiosis, in which they
  themselves were ingested
    2˚ Endosymbiosis                                    Plastid



                                                                  Dinoflagellates




                                                                                        Alveolates
                                                                  Apicomplexans
                                          Secondary
                                        endosymbiosis


      Cyanobacterium       Red algae                                Ciliates



             Primary
          endosymbiosis
                                                                  Stramenopiles


Heterotrophic                                                 Plastid
eukaryote


                                                                     Euglenids
                                          Secondary
                                        endosymbiosis
                          Green algae


                                                                  Chlorarachniophytes
            Diplomonadida and parabasala

•Have modified mitochondria
  –Are adapted to anaerobic environments

  –Lack plastids

  –Have mitochondria that lack DNA, an electron
  transport chain, or citric-acid cycle enzymes

•A tentative phylogeny of eukaryotes
  –Divides eukaryotes into many clades
Diplomonads

  –Have two nuclei and multiple flagella




                                                                       5 µm
              (a) Giardia intestinalis, a diplomonad (colorized SEM)
       Zooflagellates

· Move by flagella

· They may enter into symbiotic
  relationships with other organisms.
                 Parabasalids
-include trichomonads
  –Which move by means of flagella and an
  undulating part of the plasma membrane
                  Euglenozoa

•Have flagella with a unique internal structure

•Euglenozoa is a diverse clade that includes
  –Predatory heterotrophs, photosynthetic
  autotrophs, and pathogenic parasites

  •2 Types

  –Kinetoplastids & Euglenids
                   Euglenozoa
•The main feature that distinguishes protists
in this clade
  –Is the presence of a spiral or crystalline rod
  of unknown function inside their flagella

                       Flagella
                                  0.2 µm




                                                    Crystalline rod



                                           Ring of microtubules
                Kinetoplastids
–Have a single, large mitochondrion that
contains an organized mass of DNA called a
kinetoplast

–Include free-living consumers of bacteria in
freshwater, marine, and moist terrestrial
ecosystems
    Tsetse fly

      Trypanosoma

–Causes sleeping sickness in humans




           9 m
                                                       Euglenids
                                                                   Long flagellum


                                              Eyespot: pigmented
                                           organelle that functions
                                          as a light shield, allowing                        Light detector: swelling near the
                                           light from only a certain                         base of the long flagellum; detects
                                              direction to strike the                        light that is not blocked by the
                                                       light detector                        eyespot; as a result, Euglena moves
                                                                                             toward light of appropriate
                                                                                             intensity, an important adaptation
                                                 Short flagellum                             that enhances photosynthesis

                                                     Nucleus                            Contractile vacuole
          Euglena (LM)
                                 5 µm

                                     Plasma membrane
                 Pellicle: protein bands beneath
                      the plasma membrane that                                      Chloroplast
                  provide strength and flexibility
Figure 28.8            (Euglena lacks a cell wall)                      Paramylon granule
Euglenids
                     Euglenids

     Only one third of the species of Euglenoids are
     photosynthetic.

·   Euglena stores glucose in a polymer called Paramylon
·
    An eyespot with a photoreceptor is capable of
    detecting the presence of light.
·
    Reproduction is asexual.
                    Alveolates

Members of the clade Alveolata
  –Have membrane-bounded sacs (alveoli) just
  under the plasma membrane

                                        Alveoli
Includes:
                   0.2 µm   Flagellum



•Dinoflagellates
•Apicomplexans
•Ciliates
                     Dinoflagellates
     –Are a diverse group of aquatic
     photoautotrophs and heterotrophs

     –Are abundant components of both marine
     and freshwater phytoplankton
•Shape is reinforced by internal plates of cellulose

•Two flagella
  –Make them spin as they

  –move through the water
               Dinoflagellates
Some species are responsible for red tides that kill fish
and shellfish




                        Toxins
                        released can
                        kill aquatic
                        &
                        terrestrial
                        animals
                        (aerosols)
                 Apicomplexans
–Are parasites of animals and some cause serious
human diseases

–Are so named because one end, the apex, contains
a complex of organelles specialized for penetrating
host cells and tissues

–Have a non-photosynthetic plastid, the apicoplast
                   Apicomplexans
Most apicomplexans have intricate life cycles
–With both sexual and asexual stages that often require
two or more different host species for completion
–Plasmodium causes malaria
            Plasmodium
Anopheles
mosquito
               Sporozoans


• Parasitic

• Complicated life cycle that usually involves the
  formation of infective spores.

 e.g. malaria - The parasite is injected into a
 human by a mosquito. The parasite then invades
 red blood cells and ruptures them.
                      Ciliates
  –Are named for their use of cilia to move and feed

  –Have large macronuclei and small micronuclei

•The micronuclei
  –Function during conjugation, a sexual process that
  produces genetic variation

•Conjugation is separate from reproduction
  –Which generally occurs by binary fission
                    Ciliates
• Example - Paramecium
• The outer covering of paramecium is covered
  with hundreds of cilia

• They have numerous organelles including a
  gullet (oral groove) and an anal pore

• The macronucleus controls the cell's activities.

• The micronucleus is involved in cell reproduction
  (sexual & asexual).
                                                   CONJUGATION AND REPRODUCTION
                                           Meiosis of micronuclei
                                                 2
                                           produces four haploid
                                           micronuclei in each cell.                                  3 micronuclei in each cell
                                                                                                      disintegrate. The remaining
                                                          MEIOSIS                                     micro-nucleus in each cell
                                                                                                      divides by mitosis

                                                        Macronucleus
                                                                                   Haploid
                                                                                   micronucleus
        Compatible                               Diploid
        mates                                    micronucleus
                                                                    Diploid
                                                                    micronucleus
                                                                                                                 The cells swap
                                                                                                                 one micronucleus


                                                                                   MICRONUCLEAR
                                                                                       FUSION
                                                                                                  The cells
                                                                                                  separate
                                                                             Micronuclei fuse,
Two rounds of cytokinesis             The original macro-                    forming a diploid
partition one macronucleus          8
                                      nucleus disintegrates.    7            micronucleus.
and one micronucleus                  Four micronuclei                                                        Key
                                      become macronuclei,
into each of four daughter cells.     while the other four            Three rounds of                         Conjugation
                                      remain micronuclei.             mitosis without                         Reproduction
                                                                      cytokinesis
                                                                      produce eight
                                                                      micronuclei.
Paramecium
        FEEDING, WASTE REMOVAL, AND WATER BALANCE




50 µm
Stentor (Type of ciliate)
                  Stramenopila

•Stramenopiles have “hairy” and smooth
flagella

•The clade Stramenopila Includes:
  –Water molds

  –Diatoms                                      Hairy
                                                flagellum
  –Golden algae                     Smooth
                                    flagellum

  –Brown algae       5 µm
                 Oomycetes
–Include water molds, white rusts, and downy
mildews

–Were once considered fungi based on
morphological studies
–Are decomposers or parasites

–Have filaments (hyphae) that facilitate nutrient
uptake

–Have cell walls
made of cellulose
                    Diatoms
•Are unicellular algae
  –With a unique two-part, glass-like wall of
  hydrated silica

  –major component of phytoplankton
                   Diatoms
· Most numerous unicellular algae in the oceans
   and are an important source of food and
  oxygen.

· Also important in freshwater environments.

· Glucose stored as polysaccharide laminarin (Same
  as golden & brown algae)

· Their remains form diatomaceous earth.
  Diatoms
~ 100 000 species




                    50 µm
                                25 µm


        Golden Algae

•Or chrysophytes
  –Are named for their color,
  which results from their
  yellow & brown carotenoids

•The cells of golden algae
  –Are typically bi-flagellated, with both flagella
  attached near one end of the cell
              Brown algae
•Or phaeophytes
  –Are the largest and most complex algae

  –Are all multicellular, and most are marine

  –Include many of the species commonly called
  seaweeds

•Seaweeds
  –Have the most complex multi-cellular anatomy of
  all algae
                    Brown Algae
Photosynthetic & multicellular                              Blade

· Range in size.
Many are 50-100 m long.
· Found along rocky shores
                                                            Stipe




The thalus (plant like body) contains:                      Holdfast


· Holdfasts for attachment
· Blades and air bladders that function in floatation
· A stem-like structure that holds the blades is called a
  stipe.
Fucus
Common "seaweed" found along the rocky coast.
Brown Algae
•Kelps, or giant seaweeds
  –Live in deep parts of the ocean

  –Can grow as long as 60m



  Cell walls are composed of
  cellulose and gel forming
  polysaccharides which
  cushion the algae in the
  intertidal zone
Brown Algae - Macrocystis and
Nereocystis (Deep water Kelp)



           Nereocystis




                         Macrocystis
              A variety of life cycles
     Have evolved among the multi-cellular algae


•The most
complex life
                                                                     Sporangia




cycles include an
alternation of                                          Sporophyte
                                                                                 MEIOSIS


generations
                                                        (2n)
                                                                         Zoospores



                                                               Female

  –The alternation
                                           Developing
                                           sporophyte                     Gametophytes


  of multi-cellular
                                                                              (n)
                                              Zygote
                                              (2n)


  haploid and
                                                            Egg
                                         FERTILIZATION                                Male
                         Mature female


  diploid forms
                         gametophyte
                              (n)

                         Key                                  Sperm

                         Haploid (n)
                         Diploid (2n)
                    Cercozoans

•Cercozoans and radiolarians have threadlike
pseudopodia
•A newly recognized clade, Cercozoa
  –Contains a diversity of species that are among
  the organisms referred to as amoebas

•Amoebas were formerly defined as protists
  –That move and feed by means of pseudopodia

•Cercozoans are distinguished from most other
amoebas
                 Foraminiferans, or forams

   –Are named for their porous, generally
   multichambered shells, called tests
                                             20 µm




Pseudopodia extend through the pores in the test
                   Radiolarians
•Marine protists
  –Whose tests are fused into one delicate piece,
  which is generally made of silica

  –Phagocytize microorganisms with their
  pseudopodia
•The pseudopodia of radiolarians, known as
axopodia
  –Radiate from the central body




           Axopodia

                                    200 µm
               Radiolarians

  Marine plankton (float in marine environments) with
a skeleton composed of silica, and numerous needle-
like pseudopodia.
                Amoebozoans
• Have lobe-shaped pseudopodia
  –rather than threadlike, pseudopodia

  –Include gymnamoebas, entamoebas, and slime
  molds
              Protozoans
· Do not have a cell wall

· Heterotrophic

· Usually motile

· Food vacuoles

· Contractile vacuole (water elimination)

Reproduction is usually asexual but many also reproduce
  sexually during some part of their life cycle.
                 Gymnamoebas

 –Are common unicellular amoebozoans in soil as
 well as freshwater and marine environments


                                          Pseudopodia


•Most are                         40 µm




heterotrophic
  –And actively seek
  and consume
  bacteria and
  other protists
                         Entamoeba

  –Are parasites of vertebrates and some invertebrates

•Entamoeba histolytica

  –Causes amebic dysentery in humans
                  Amoeboids
Amoeba

 Move by cytoplasmic extensions called pseudopodia.

 Feed by phagocytizing (engulfing) their prey.

Most amoeboids are marine organisms;

Amoeba proteus is found in freshwater
Amoeboids
             Slime molds, or mycetozoans


  –Were once thought to be fungi

•Molecular systematics
  –Places slime molds in the clade Amoebozoa

  –Plasmodial & Cellular types
           The plasmodium
–Is undivided by membranes and contains
many diploid nuclei

–Extends pseudopodia through
decomposing material, engulfing food by
phagocytosis
          Protists that are Decomposers
                   (Saprotrophs)
·    Slime molds play an ecological role similar to that of fungi.

·   They are decomposers, feeding on dead organic material.

·   They differ from fungi in that slime molds ingest their food.

·    Slime molds are masses that creep along the substrate and phagocytize
    dead organic material and microorganisms.

·     The mass is one large cell referred to as a plasmodium.

·     Spores are resistant to environmental extremes (Food and moisture)
    and germinate when environmental conditions become favorable

·     Saprotrophic; they live off of dead organic matter.
Slime Molds
Plasmodial Slime mold life cycle


                       Feeding          Mature
                       plasmodium       plasmodium
                                        (preparing to fruit)
    Zygote
    (2n)
                                                 Young
     SYNGAMY                                     sporangium


                                                                                       1 mm


                       Amoeboid cells                     Mature
                       (n)                                sporangium

                                                                                 Key
                            Germinating          Spores        MEIOSIS
                                                 (n)                             Haploid (n)
                            spore
   Flagellated cells                                                             Diploid (2n)
   (n)                                                                   Stalk
                 Cellular slime molds

•Form multicellular aggregates
  –In which the cells remain separated by their
  membranes

  –Has become an
  experimental
  model for
  studying the
  evolution of
  multi-cellularity
Cellular Slime Mold                                Life Cycle

                                           SYNGAMY

                      Emerging
                                                 Zygote
               Spores amoeba
                                                 (2n)
               (n)                       SEXUAL
                                         REPRODUCTION
                     Solitary amoebas
600 µm                                                 MEIOSIS
                     (feeding stage)
                                             Amoebas
                    ASEXUAL
         Fruiting   REPRODUCTION
         bodies
                        Aggregated
                        amoebas

                    Migrating
                    aggregate




                                                                 Key
                                                                 Haploid (n)
                                        200 µm                   Diploid (2n)
                        Algae

The word algae refers to aquatic (freshwater or marine)
  protists.

 Algae photosynthesize like plants. They produce much
  of the oxygen in the atmosphere.

· Algae provide food for aquatic food chains.
                  Red & Green Algae
•Are the closest relatives of land plants

•Over a billion years ago, a heterotrophic protist
acquired a cyanobacterial endosymbiont

  –And the photosynthetic descendants of this ancient
  protist evolved into red algae and green algae
                     Red Algae
• Are reddish in color
  –Due to an accessory pigment call phycoerythrin,
  which masks the green of chlorophyll
                    Red Algae


• Red algae are found mainly in warmer, tropical oceans.

• Accessory photosynthetic pigments are called
  phycobilins which allow some species to survive in deep
  waters where blue and green light predominates.

• Some species are filamentous but most have a complex
  pattern of branching.

• Some coralline forms deposit calcium carbonate in
  their cell walls, making coral reefs.
                  Green Algae
–Are named for their grass-green chloroplasts

–Are divided into two main groups: chlorophytes
and charophyceans

–Are closely related to land plants
             Green Algae

Single-celled and multicellular forms.
·
Ancestors of the first plants, both have the following
  characteristics in common:
They have a cell wall that contains cellulose.
They have chlorophyll
They store their food as starch inside the chloroplast.
                          Chlorophytes
                          (green algae)
•Include:
  –Unicellular,
                                      20 µm
                  50 µm




  colonial, and
                                              (a)




  multi-
  cellular
  forms

                  )
                    Ulva
• Multicellular with a leaf-like body that is
  two cells thick but up to one meter long

• Common name: Sea lettuce
                     Volvox


· Colonial green algae
· They divide asexually to
   produce a daughter colony.

Notice the daughter colonies
  within the larger colonies.
                     Volvox


• Some cells are specialized to produce sperm
  and eggs for sexual reproduction which is a
  characteristic of multicellular organisms.

• Considered to be a colony because it appears
  to be intermediate between a group of
  individual cells and a multicellular organism.
              Spirogyra

· Filamentous form of green algae.

· Has a ribbonlike spiral-shaped chloroplast.

· Sexual reproduction occurs by conjugation.
  ·

The zygote is resistant and overwinters.
        Spirogyra




Conjugation
                  Chlorophyte Life Cycle
                                                           Harsh environmental
                                                           conditions
   Flagella
                         1 µm                                  
  Cell wall


  Nucleus                                              +
                                                               +         

                                Zoospores
                                                                    SYNGAMY
                                               Mature cell
                                ASEXUAL        (n)
                                                     SEXUAL
Regions                         REPRODUCTION         REPRODUCTION
of single                                                                     Zygote
chloroplast                                                                   (2n)



                                                   +       


         Key                                   +               MEIOSIS

       Haploid (n)
       Diploid (2n)



                      Normal environmental
                      conditions
          Protists Compared to Plants,
               Animals, and Fungi
• Characteristics resemble plants, animals, or fungi.

• Photosynthetic protists differ from plants in that they do
  not have structures that protect the gametes or zygote.

• Plants and animals undergo a period of embryonic
  development but protists do not.

• Fungi have cell walls composed of chitin; protists do not
  have chitin in their cell walls

• Fungi do not have cilia or flagella. Many kinds of protists
  have cilia or flagella.
           Trophic Levels
    Autotrophs:            Heterotrophs:
·    green algae       ·     amoeboids
·    brown algae       ·     ciliates
·    red algae         ·     zooflagellates
·    diatoms           ·     sporozoans
·    dinoflagellates   ·     slime molds
·    euglenoids

				
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