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types of protist

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					                 Kingdom Protista
A very large and diverse group - comprising at least 16 phlya
A paraphyletic group - it does not contain all of the descendants
of the common ancestor of this group - some descendants are
multicellular - the fungi, plants, and animals
Many of the protists groups did not give rise to multicellular
organisms - at least 13 phyla have have remained single celled
Current classification is changing and likely to change greatly in
the near future.
Sixteen Phyla comprise the Kingdom Protista
classically grouped into 5 informal groups based on mobility and
nutrition - differs from evolutionary estimates of relatedness
Protistan Diversity
The Cell Surface
  Amoebas lack a cell wall
  Algae and slime molds encased in strong cell walls
  Diatoms and Foraminiferans have shells of silica, calcium, debris
Locomotor Organelles
  Many move by flagellar motions, or ciliary action, pseudopodial
  movement - many are immobile
Nutrition
  Phototrophs and Heterotrophs (phagotrophs (ingesters) and
     saprobes)
Reproduction
  Asexual reproduction by mitosis, fission, budding, spores
  Sex by gametic meiosis, zygotic meiosis, or sporic meiosis
The Sarcodines - all can have pseudopodia
    Phylum Rhizopoda - the amoebas
    Phylum Actinopoda - actinopods, heliozoans
    Phylum Foraminifera - forams
Phylum Rhizopoda - the amoebas
Heterotrophic
Fresh and salt water, abundant in soil, some parasitize animals
Reproduction by simple mitotic fission
No cell walls, flagella, sexual reproduction
Locomotion via pseudopodia
Pseudopodia also used for prey capture



Parasitic species may form resistant cysts
   Entamoeba histolytica : Causes amoebic dysentery
   Cysts resist digestion by host
   Carriers exhibit no symptoms but can spread cysts
   Spread through fecal contamination in food or water
       may be dispersed by flies
Phylum Actinopodia - Actinopods -
silica (glass) skeletons covering most of cell
with many thin needlelike pseudopods that
project through pores
Phylum Foraminifera - Forams
Heterotrophic, marine organisms
Possess pore-studded shells called tests
 tests: organic matter reinforced with inorganic
    usually multichambered, often spiral shaped
    material: often calcium carbonate, can use sand grains,
       echinoderm plates, sponge spicules
Podia extrude through pores in test - used for swimming,
   gathering material for test, feeding

                                                   White Cliffs of
                                                   Dover - chalk
                                                   formed from
                                                   deposited forams
Algae and other photosynthetic protists

Phylum Chlorophyta - green algae
Phylum Rhodophyta - red algae
Phylum Pheophyta - brown algae
Phylum Chrysophyta - golden algae
   and diatoms
Phylum Pyrrophyta - dinoflagellates
Phylum Euglenophyta - euglenoids
Phylum Chlorophyta: Green Algae
Ancestors of all plants were multicellular green algae
green algae and plants use chlorophylls a and b, carotenoids
found in aquatic and semiterrestrial habitats
Unicellular and multicellular forms
Chlamydomonas is a
typical unicellular form
   biflagellated
   light sensitive eye-spot
   zygotic meiosis with
   zygospore resting stage
Some green algae are motile and
colonial like Volvox
Specialized reproductive cells give rise
to new colonies within the parent
colony
Has zygotic meiosis and zygospores
form within a parent colony.



Some green algae are
filamentous - like Spirogyra
   named for its spiral
   chloroplasts
Sex is through conjugation
of cells from + and - strains
Some green algae, like Ulva, form
multicellular sheets and have sporic
meiosis




                                       Except for their ploidy,
                                       the gametophytes and
                                       sporophytes are very
                                       similar
Phylum Rhodophyta - Red Algae
Most common coastal seaweeds - mostly multicellular, common in
warm waters
Chloroplasts have Chlorophyll a and phycobilins, like cyanobacteria

Absorb green, violet and blue light
Grow at greater depths than other algae
have sporic meiosis
Completely lack flagella
Body composed of interwoven filaments
An ancient group of eukaryotes
Economic importance
Some make sulfated polysaccharides like agar and carrageenan
Agar used as laboratory medium, a base for cosmetics, used in
baked goods and as a temporary preservative for meat and fish
Carrageenan used in paints, cosmetics and ice cream
Phylum Phaeophyta - Brown Algae
Mostly multicellular and marine
Conspicuous seaweeds, include kelps and Sargassum
Use chlorophylls a and c (like diatoms)
Photosynthetically productive - fast growing
Provide food for many animals
Some kelps grow up to 100 meters in length
Have sporic meiosis
   sporophyte: large, conspicuous kelp-like form
   gametophyte: small, filamentous form
   separate male and female gametophytes
Phylum Chrysophyta - Diatoms and Golden Algae
Diatoms are photosynthetic, unicellular organisms
Double shells of silica - Resemble box with lid
Use chlorophylls a and c, and carotenoids
fossilize well - thick sediments of fossil
  diatoms are called “diatomaceous earth”
Some move by secretions from shell
Asexual reproduction separates shell halves
  each half produces new shell within old
one - become smaller with each division
Have gametic meiosis - cells are diploid
  and produce sperm or eggs by meiosis
Golden Algae - use yellow and brown carotenoid pigments, and
   xanthophyll accessory pigments
Unicellular, two flagella, often colonial, common in freshwater
Form resistant cysts when ponds dry out in summer
 Phylum Pyrrhophyta - Dinoflagellates
 Unicellular, photosynthetic, mostly marine, some bioluminescent
 Distinctive flagella and coat
    two flagella beat in grooves
    coat composed of cellulose plates
 Most use chlorophyll a & c and carotenoids
 Some are symbiotic with animals
    sea anemones, mollusks and corals
    in corals - called “zooxanthellae”,
        required for formation of coral reefs
 Some forms cause “red tide”
    large blooms result in red colored water
    release toxins that kill fish and shellfish
    consumption of poisoned fish can kill
Reproduce primarily asexually by longitudinal cell division with
    nuclear mitosis - like fungi
Phylum Euglenophyta - Euglenoids
Mostly fresh water organisms
Group has characteristics of plants and animals
Some specimens are photosynthetic
  use chlorophylls a and b, and carotenoids
Others lack chloroplasts and are heterotrophic
Some can transform from autotrophs to
  heterotrophs and back, depending on
  presence of light and food
Reproduction via nuclear mitosis and cell
  division
No sexual reproduction known
Euglena is typical
Thin flexible pellicle lies within cell membrane - composed of
   interlocking strips of protein
have two flagella - both
   with bases in reservoir -
   one is very small
Contractile vacuoles collect
   and pump out excess
   water at reservoir
have light sensitive stigma
paramylon granules are
   for food storage
Heterotrophs with flagella or cilia -
Phylum Sarcomastigophora - Zoomastigotes
Unicellular, heterotrophic, highly variable in form
Possess one to thousands of flagella
Some free-living, some parasitic
Some reproduce asexually only
One group alternates between amoeboid and
  flagellated stages
Some trypanosomes are human pathogens
  cause sleeping sickness, East Coast fever,
  Chagas' disease
  many spread by insects, such as tsetse flies
Some inhabit guts of wood-eating insects
  have enzymes capable of digesting cellulose
Choanoflagellates are similar to feeding cells of
  sponges and are likely ancestors of all animals
Hiker's Diarrhea:
Caused by Giardia lamblia, found world-wide
Occurs in water, infects wild and domesticated animals, and
   humans
Lives in small intestine of host
Spreads as cysts in feces, can survive for months in cool water
May appear in city water supplies
Resistant to treatment with chlorine and iodine, requires boiling
water to kill
Phylum Ciliophora - The Ciliates
Unicellular, heterotrophic, with many cilia
   Coordinated beating provides motility
Outer pellicle is tough but flexible
Two types of nuclei
   micronuclei - diploid - reserved for sex
   macronuclei - polyploid - for normal
       cellular metabolism
Specialized vacuoles ingest food and contractile
   vacuoles regulate water balance
Food enters through gullet (cytostome) and
   passes into vacuoles where it is digested
Asexual reproduction by transverse
  fission


Sexual reproduction by conjugation
Two different mating types
  exchange haploid micronuclei
Macronucleus in each individual
  disintegrates
Multiple rounds of chromosomal
  replications in micronuclei
  reconstitutes macronucleus
Phylum Apicomplexa - Sporozoans
Nonmotile, spore-forming animal parasites
Have an “apical complex” at one end of cell - with fibrils,
    microtubules, and vacuoles - used to enter host cells

Have complex life cycles with
   sexual and asexual phases
Exhibit alternation of haploid and
   diploid generations
Fusion of gametes produces a
   thick-walled cyst, the oocyst
Meiotic divisions in oocyst
   produce infective haploid
   spores, sporozoites
Plasmodium causes malaria

Gametocytes
become
gametes in
gut of
mosquito
syngamy
forms zygote
and oocyst
meiosis in
oocyst forms
sporozoites
Malaria
estimated that 500 million infected, 200 million humans die
     each year, most infected children die

symptoms include chills, fever, sweating, enlarged spleen,
     confusion, thirst - repeating every 48 to 72 hours
Victims die of anemia, kidney failure, brain damage

Effects can be reduced with drugs

Focus is on eradication of malaria through elimination of
    mosquito carriers

Vaccines against malaria may be available in near future
Slime Molds

Phylum Acrasiomycota - Cellular
Slime Molds
Phylum Myxomycota -Plasmodial
Slime Molds
Phylum Oomycota - water molds,
rusts, mildew
Phylum Acrasiomycota - Cellular Slime Molds
Once thought to be related to fungi
  most closely related to amoebas
Common in fresh water, damp soil, rotting vegetation
Usually found as free
 living amoebas
Sometimes cells aggregate
 into motile slug
Slug transforms into
 sorocarp,
within sorocarp some
 amoebas fuse sexually
 forming diploid
 macrocysts
meiosis occurs in macrocysts - spores released form new amoebas
Phylum Myxomycota -Plasmodial Slime Molds
Consist of streaming multinucleate plasmodium
   feeding phase may be yellow, orange or other color
Cytoplasm exhibits conspicuous streaming
Engulf and digest bacteria, yeast, bits of organic matter
forms sporangium under adverse conditions
Phylum Oomycota - water molds, rusts, mildew
Live in freshwater or soil, many are plant or animal parasites
Cell walls are composed of cellulose or similar polymers
Body consists of filamentous hyphae
Hyphae are diploid (unlike fungi) and produce gametes by meiosis
Exhibit normal mitosis (unlike fungi)
have unique life cycle
Diploid spores produced asexually in sporangium
Sex: female gametangium called oogonium with one to eight eggs
       male gametangium called antheridium with many sperm
       Fusion produces zygote that becomes thick-walled oospore
       oospore germinates and forms new hypha

				
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posted:3/29/2009
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