Origin and Diversification of Eukaryotes: Protists

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Origin and Diversification of Eukaryotes
Protists

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Eukaryotic Cells

• Nucleus and membrane bound organelles
• Well developed cytoskeleton structural support
  that lends to asymmetric forms
• May have originated more than 2.7 bya, but 1.8
  bya widely accepted

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3 stages of diversity documented by fossil
records

• Initial diversification 1.8 1.3 bya
• Origin of multicellularity 1.3 bya 635 mya
• Emergence of large eukaryotes 635-535 mya

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endosymbiosis

• Symbiotic relationship in which one organism
  lives inside the bosy or cell of another
  organism.
• DNA sequence data suggest that eukaryotes are
  combination organism from Archaea and Bacteria
• Endosymbiont theory mitochondria and plastids
  were formerly small prokaryotes that began living
  within larger cells. (See page 485)

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Multicellularity

• Colonies collection of cells that are connected
  but show little or no cellular differentiation.
• Multicellular organisms with differentiated cells
  Algae, plants, fungi and animals

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Characteristics

• Most diverse kingdom
• eukaryotic., 1.5 bya
• Primarily unicellular/multicellular,
• heterotrophic/autotrophic
• Usually asexual, some sexual
• Found in water, damp soil and sand, leaf litter
• Some are parasitic
• 14 phyla

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Characteristics

• Characteristics first seen in Protista kingdom
• Sexual reproduction (varies, mitosis and meiosis
  usually in harsh enviro.)
• Multicellularity (coordination among specialized
  cells)
• Complex flagella and cilia (as opposed to simple
  seen in bacteria)

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Protist diversity

• Heterotrophic protists protozoans, slime molds,
  water molds, parasites
• Photosynthetic protists Algae
• Some are classified further by how they move
• Amoebas pseudopodia
• Ciliates cilia, ex. paramecium
• Flagellates flagella, ex. Euglena

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Algae Green, Red and Brown

• Strict autotrophs, some multicellular
• Distinguished by type of pigment they contain
• Red
• Multicellular, warm ocean waters
• Red pigment can absorb light in deep water
• Brown
• Multicellular, marine
• Kelp, grows along coasts, food and shelter
• Green
• Most freshwater, uni and multicellular
• Contains chlorophyll a and b

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Green Algae

• Phylum Chlorophyta
• Most unicellular, can be filamentous or colonial
• Chlamydomonas unicellular green algae
• Spirogyra filamentous green algae
• Ulva multicellular green algae (sea lettuce)
• Volvox colonial (loose association of
  independent cells) green algae

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Red Algae/Brown Algae

• Phylum Rhodophyta
• Economically important
• Agar
• Wrappings around sushi
• Emulsifying agent for production of chocolate
• Phylum Phaeophyta
• Contain chlorophylls a and c and carotinoid
• Kelp, rockweed grow along shoreline
• Harvested for human food and fertilizers
• Algin pectin-like material added to icecream

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Diatoms

• Phylum Chrysophyta includes golden-brown algae
  and yellow-green algae
• Photosynthetic, significant part of
  phytoplankton, Important to food chain
• Double shell made out of silica, like hat box
• Move by excreting chemicals through Diatomaceous
  earth
• abrasives
• holes in shell
• Found in oceans and lakes

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Dinoflagellates

• 2 flagella, cellulose plates
• Unicellular
• Most are marine, make up part of the plankton,
  important food source, producers
• Some produce powerful toxins red tide

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Euglena

• Freshwater, unicellular with 2 flagella
• Some photosynthetic with chloroplasts and has
  ability to ingest food as well
• Pellicle protein fiber inside cell membrane,
  allows for flexibility and shape change
• Eyespot light sensitive organ, toward light
• Contractile vacuole
• expels excess water

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Zooflagellates

• Mostly unicellular, hetertrophic protozoans
• Symbiotic and parasitic forms
• Trypanosomes transmitted by tsetse fly
• Causes African Sleeping Sickness
• Giardia lamblia cysts from contaminated water,
  intestinal wall, severe diarrhea
• Trichomonas vaginalis STO, infects vagina and
  urethra of women, prostate of males

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Amoeba

• Pseudopodia false foot, cytoplasmic extensions
• Food vacuole food enters and moves throughout
  cell
• Contractile vacuole regulates water
• Entamoeba histolytica amoebic dysentery

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Forams

• marine protist that lives in sand or attaches to
  other organisms
• Tests porous shells
• Thin projections of cytoplasm extend through
  pores and aid in swimming

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Paramecium

• Freshwater streams and ponds
• Unicellular, heterotrophic
• Cilia to move
• Two nucluei
• Macro cell activities, includes DNA
• Micro cell reproduction, contains chromosomes

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Sporozoans parasitic protists

• Form spores during their reproductive cycle
• Nonmotile, spore forming, unicellular parasites
• Malaria anopheles mosquito, pg 392
• Toxoplasma gondii toxoplasmosis,
• during pregnancy,
• can affect fetus

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Slime molds - decomposers

• Cellular slime mold, small
• Behave like amoebas
• Ingest bacteria
• During stress, form multicellular colonies
• Plasmodial slime molds
• Mass of cytoplasm that looks like ooze, colorful
• Eat bacteria and other organic material,
  phagocytes

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Water Molds

• Filamentous decomposers
• Parasitic to plants and animals in ecosystems
• Cell wall contains cellulose, not chitin
• Usually have furry growths
• Responsible for potato famine in Ireland, 1840s

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Beneficial protists

• Commensal protists that live in digestive tracts
  of humans and livestock (hay, cellulose)
• Plankton food, shelter, producers
• Largest group of photosynthesizers
• Abrasives
• Detritivores recycle chemicals in environment
• Symbiotic relationships - coral