Protists

Protists:

• Protists: Unicellular eukaryotic organisms.

• Over 115,000 species

• Eukaryotic cells - contain membrane-bound organelles (particularly mitichondria & chloroplasts)

• Protists & eukaryotes probably evolved from a large eukaryotic cell ingesting a photosynthetic and oxygen metabolizing bacteria
• Known as endosymbiotic theory
• Three major classes of protists

1. Animal-like protists
2. Plant-like protists
3. Fungus-like protists

Animal-like Protists
Phylum Ciliophora (Cilia bearing protists)

• Aka "ciliates"
• Have cilia (short hairlike structures) on their plasma membranes


• Cilia rapidly beat and provide propulsion for the protist.
• Over 7000 species in this phylum.
• Example is paramecium.

• Large organisms ~305 micrometers long
• Important features:
• Have 2 nuclei
• Macronucleus (large)
• Micronucleus (smaller)
• Feed by forcing H2O into Gullet forming food vacuoles
• Excrete wastes through anal pore
• Excrete excess water through use of contractile vacuoles.

Phylum Sporozoa

• Usually parasitic in nature
• Example is Plasmodia which causes malaria.
• Malaria is transmitted by the Anopheles mosquito.
• Spores infect liver cells
• Liver cells lyse releasing plasmodium cells which infect blood cells

Plasmodia Lifecycle

Plasmodia inside liver cell

Phylum Sarcodina (Protists with false feet)

• .

Plant-like Protists

• 5 phyla of plant-like protists.
• All are unicellular, most are motile
• Most are photosynthetic and heterotrophic

Single Cellular Algae

• Are all photosynthetic
• Lack advanced plant tissues since they are unicellular
• Major source of organic molecules and O₂ for the planet.

Examples:

• Dinoflagellates
  • Have 2 flagella for motility
  • Often have a cellulose covering 

• Diatoms
  • Most abundant form of marine algae.
  • Form elaborate silicon (glass) shells to protect themselves
  • Shell is porous to allow materials in/out of the cell.

Diatoms

• Phylum Euglenophyta
  • Example is euglena.
  • Has a flagellum, is motile
  • Is both heterotrophic & autotrophic
  • Contains chloroplasts & is photosynthetic.
  • Can become heterotrophic in low-light conditions

euglena

Multicellular Algae

• Are not generally true multicellular organisms, but rather "colonies"
• Show beginnings of specialized functions / tissues
• 3 types
  • Green algae (Chlorophyta)
    • contain chlorophyl a & b
    • Most frequently found in fresh water
    • Often colonial
    
    Volvox (colonial green algae)
  • Red Algae (Rhodophyta)
    • Found in salt/brackish water
    • Have additional pigments which give them a reddish color.
    • In uncontrolled blooms, these organisms can cause serious ecological damage

Red Algae 

• Brown Algae (Rhodophyta)
  • Most Plant-like of all algae.
  • Include kelps
  • Can grow to huge sizes (100')
  • Most primitive plant like organism to show alternation of generations.
  
  Kelp forest

Fungus like Protists:

• Act as decomposers
• Often have a slimy appearance/texture, hence their name.
• 3 types:
  • Plasmodial slime molds
  • Cellular slime molds
  • Water molds
  
  
• Plasmodial Slime Molds
  • Can grow very large, however, is still a single cell (with many nuclei)
  • Feeding stage is called a plasmodium.
  • Forms fruiting bodies under stress.
• 
  

• 
  

• Cellular Slime Molds:
  • Exists a majority of its life cycle as an amoeba
  • In  times of stress these amoebas unite to form a Pseudoplasmodium, which crawls to another location (slug form), and forms a fruiting body

Cellular Slime mold life cycle

• Water molds:
  • Completely aquatic
  • Often decomposers
  • Sometimes parasitic
  
  Water mold attacking a fish
  
  
  http://chsweb.lr.k12.nj.us/