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Protists

By Brian Kato, Adam Resnick, and Yukako Kawakatsu

Introduction

• • • Protists are a diverse group of eukaryotes that are not animals, plants or fungi.

They can be unicellular or multicellular, but do not have any specialized tissues.

It is hard to come up with a specific definition of a protists owing to their diversity.

Endosymbiosis

• • • Endosymbiosis is a theory which explains the origins of plastids in eukaryotes.

It states that chloroplasts and mitochondria evolved from small bacteria engulfed by larger bacteria.

The small bacteria remained alive within the large ones, and they developed a symbiotic relationship.

Secondary Endosymbiosis

• • • A larger organism engulfs a smaller one which has already undergone endosymbiosis.

This explains the diversity of plastids which are found in protists.

It is more difficult to determine which plastids were acquired through secondary endosymbiosis in organisms which underwent this process in the distant past.

Phylogeny

• • • • • • • • • Protozoa Similarities to Animals: ･ Mobility, digestion, ingestion Algae Similarities to plants: ･ Chloroplasts (produce own food), thallus (parts that correlate to plant structure) Differences: ･ Lack leaves, roots, flowers, and other organ structures.

Fungus-like Similarities to fungus: Reproduce by spores Have hyphae (branch-like structure used to absorb nutrients) Difference: Use different materials in their cell walls-protists use cellulose, fungi use chitin.

They can behave as amoebas at times, while fungi grow as a single stationary unit.

• • • • • • • Diplomonads Two equal-sized nuclei Multiple flagella Ex:

Giardia

Parabasalids Undulating membrane Similarities: Modified mitochondria Lack plastids Most found in anaerobic environments

Euglenozoans

• • • • Predatory heterotrophs, photosynthetic autotrophs, and pathogenic parasites Spiral or crystalline rod inside flagella Kinetoplastids: have kinetoplast (DNA in mitochondria) • ex: Trypanosomes-sleeping sickness ( “bait-and-switch” defense) Euglenids: have paramylon as storage molecule. Switch between heterotrophs/ autotrophs according to availability of nutrients and sunlight(eyespot).

Alveolates

    Alveoli beneath plasma membrane Dinoflagellates: armor of cellulose plates Apicomplexans: apical complex of organelles Ciliates: cilia used in movement and feeding; macro and micronuclei.

Stramenopiles

  Hairy and smooth flagella Oomycetes: hyphae that absorb nutrients  Diatoms: glassy, two-part wall  Golden algae: flagella attached near one end of cell  Brown algae: all multicellular, some with alternation of generations

Cercozoans and Radiolarians

   Amoebas with threadlike pseudopodia Forams: porous shell Radiolarians: pseudopodia radiating from central body

Amoebozoans

     Amoebas with lobe-shaped pseudopodia Gymnamoebas: soil-dwelling, freshwater, or marine Entamoebas: parasites Plasmodial slime molds: multinucleate plasmodium; fruiting bodies that function in sexual reproduction.

Cellular slime molds: multicellular aggregate that forms asexual fruiting bodies.

Red Algae

  Phycoerythrin (accessory pigment) No flagellated stages

Chlorophya (green algae)

 Plant-type chloroplasts

Ciliate Life Cycle

Plasmodium Life Cycle

The Life Cycle of a Water Mold

Life Cycle of Multicellular Algae

(Alternation of Generation)

Life Cycle of Plasmodial Slime Mold

Life Cycle of Cellular Slime Mold

Life Cycle of Unicellular Chlorophyte

Biological Niche

     Parasites (ex: malaria, sleeping sickness, dysentery) Dinoflagellates  Red tide  Mutualistic symbionts of coral polyps and the giant clam Water molds (oomycetes)  Potato late blight Diatoms  Diatomaceous earth mined as filtering medium  Nanotechnology-microscopic devices Algae  Food (seaweed, soups, used to thicken pudding, ice cream, salad dressing)    Forests house marine creatures Watermelon snow Live symbiotically w/in other eukaryotes-contribute part of their photosynthetic output to food supply of hosts (lichens)

Reference

                 http://www.biology.ualberta.ca/courses.hp/zool250/Clades/clade01-Protista.htm

http://www.biology.ualberta.ca/courses.hp/zool250/Clades/CladePics/Giardia.jpg

http://www.wwdd2.net/trichomonas.bmp

http://courses.bio.psu.edu/fall2005/biol110/tutorials/tutorial27.htm

http://staff.tuhsd.k12.az.us/tcochran/BioImages/ciliate.jpg

http://www.vialattea.net/spaw/Image/biologia/Paramecium.jpg

http://microscope.mbl.edu/baypaul/microscope/taxonomy/Stramenopiles/hairflag.jpg

http://daviddarling.info/images/diatoms.jpg

http://www.laups.org/gallery2/d/934-1/perch-in-kelp-forest.jpg

http://www.spectrosciences.com/IMG/jpg/formaminifere.jpg

www.sanvalero.net/.../foram%201.JPG

http://www.bms.ed.ac.uk/research/others/smaciver/amoeba.htm

http://www.nsf.gov/od/lpa/news/03/images/amoeba_spore_tower.jpg

http://www.ucmp.berkeley.edu/protista/reds/porphyra.gif

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