Eukaryotes

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Eukaryotes

• Protista

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What do Eukaryotes have that Prokaryotes do not?

• Membrane-bound nucleus
• Mitochondria, chloroplasts, and endomembrane
  system
• Cytoskeleton
• Flagella of microtubule construction
• Multiple chromosomes of linear DNA compactly
  arranged with proteins
• Diploid life stages
• Mitosis and Meiosis and Sex

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Compartmentalization of functionsoccurs in
eukaryotes
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Endosymbiotic theory of eukaryotic evolution

• Evidence of mitochondria and chloroplast origin
• Appropriate size
• Replication by binary fission
• Inner membranes containing enzymes and transport
  systems similar to prokaryotic plasma membranes
• DNA is circular and not complexed with histones
• Have their own ribosomes, tRNAs and other
  components for transcription/translation
• Ribosomes are more similar to prok. than euk.

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A model of the origin of eukaryotes
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Protistan taxonomy is in a state of flux (a mess)

• Your Lab book and your text book approach
  protists in very different manners using
  different terminology.
• Your lab book is the more classic approach and
  we will follow that more closely

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Traditional hypothesis for how the three
domains of life are related
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An alternative hypothesis for how the three
domains of life are related
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A tentative phylogeny of eukaryotes (Campbell
6th Edition)
We are going to look at protists using a more
Classic, simpler scheme
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First a couple definitions

• Plankton
• Communities of organisms, mostly microscopic,
  that drift passively or swim weakly near the
  surface of oceans, ponds, and lakes
• Encystment
• Cyst formation
• A response to adverse conditions
• Allows a parasitic species to survive outside a
  host, allows others to survive hostile
  environmental conditions
• Only some protists can do this

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Archezoans

• Lack mitochondria or chloroplasts
• Have prokaryotic-like ribosomes
• Simple cytoskeletons

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Archezoans

• Giardia lamblia
• Unicellular flagellate. Most commonly transmitted
  in the cyst form through water contaminated with
  human feces

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Trichomonas vaginalis An inhabitant of vaginal
tract of human females. Can be sexually
transmitted. Has flagella and an undulating
membrane for movement
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The Protozoa (animal-like protists)

• Diverse group of heterotrophic protists
• Classically grouped into different Phyla based
  upon their movement and how they feed

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The Protozoa Rhizopoda the amoebas

• Very simple protists, unicellular
• Pseudopodia
• Entamoeba histolytica
• ( human pathogen)

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Amoeba proteus
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Use of pseudopodia for feeding
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The Protozoa Actinopoda (Helizoans and
Radiozoans)

• Axopodia projections reinforced by bundles of
  microtubules thinly covered by cytoplasm
• Most are planktonic
• Heliozoans fresh water
• Radiozoans- marine, silica shells

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Actinopods Heliozoan (left), radiolarian (right)
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Radiolarian skeleton
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The Protozoa Foraminifera (Forams)

• Marine organisms
• Porous shells of organic material hardened by
  calcium carbonate
• Many have algae living beneath the shell which
  provide nutrients via photosynthesis

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Foraminiferan
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The Protozoa Apicomplexa (Sporozoans)

• All species are obligate intracellular parasites
  of animals
• Toxoplasma gondii
• Toxoplasmosis
• Cryptosporidium
• Diarrhea. Transmitted via fecal contamination
• Water supply outbreaks have been reported
• Plasmodium
• Malaria

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The two-host life history of Plasmodium, the
apicomplexan that causes malaria
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The Protozoa Zoomastigophora (flagellates)

• Move by whip-like flagella
• Trichonympha
• Inhabits the gut of termites
• Trypanosoma
• Hemoflagellate
• African Sleeping sickness

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Trichonympha
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Trypanosoma, the kinetoplastid that causes
sleeping sickness
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The Protozoa Ciliophora (ciliates)
Stentor
Paramecium

• Move by cilia
• Most are free-living in fresh water
• Paramecium
• Stentor
• Vorticella

Vorticella
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Ciliates Paramecium
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Fungus-like Protists

• Filamentous body structure at times makes them
  appear to be like molds, but they are more
  closely related to amoebas than to true fungi.
• Myxomycota (plasmodial slime molds)
• Acrasiomycota (cellular slime molds)
• Oomycota (water molds, white rusts, downy mildews)

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The life cycle of a plasmodial slime mold, such
as Physarum
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Plasmodial slime mold
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Slime mold Sporangia
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The life cycle of a cellular slime mold
(Dictyostelium)
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Dictyostelium life cycle
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Stages of Dictyostelium
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The life cycle of a water mold (Layer 3)
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Water mold Oogonium
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Powdery mildew
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Algae

• Diverse group of photoautotrophic aquatic
  organisms
• Major role in aquatic food chains
• Fix carbon dioxide into organ carbon
• Produce somewhere between 50 and 80 of the
  Earths oxygen

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AlgaeDinoflagellata (dinoflagellates)

• They have two flagella and may have armor
  (cellulose plates) or may be naked (without
  armor). Dinoflagellates have pigments and can
  carry on photosynthesis. Major component of
  phytoplankton.
• Gonyaulax
• Red tide
• Paralytic shellfish poisoning
• Peridinium (lab)
• Noctiluca miliaris
• Bioluminescent

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Dinoflagellate
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Dinoflagellates
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Swimming with bioluminescent dinoflagellates
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AlgaeBacillariophyta (Diatoms)
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a diatom, a unicellular "alga"
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Chrysophyta Golden algae
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Phaeophyta (Brown algae)

• Largest and most complex of the algae
• Kelp is a brown algae
• Giant kelp - up to 100 meters in size
• Seaweeds large, multicellular marine algae of
  coastal waters which include members of the
  Brown, Red, and Green algae groups

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Australian bull kelp (Durvillea potatorum)
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Kelp forest
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Kelp forest
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Red algae Dulse (top), Bonnemaisonia hamifera
(bottom)
Rhodophyta Red Algae
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Chlorophyta (green algae)

• Over 7000 species known
• Freshwater and marine
• Unicellular and multicellular forms
• Chlamydomonas
• Volvox
• Spirogyra
• Cladophora
• Lichensa mutualistic relationship between a
  green algae and a fungus

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Colonial and multicellular chlorophytes Volvox
(left), Caulerpa (right)
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Chlamydomonas
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Volvox
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Spirogyra
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Chladophora
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Lichens