Photosynthesis

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Outline

• Protist Biology
• Protist Evolution
• Protist Diversity
• Green Algae
• Red Algae
• Brown Algae
• Diatoms
• Dinoflagellates

• Protist Diversity, cont.
• Euglenoids
• Zooflagellates
• Pseudopods
• Ciliates
• Sporozoans
• Slime Molds
• Water Molds

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General Biology of the Protists

• Classified into the Domain Eukarya the Kingdom
  Protista
• Morphology
• Most unicellular
• Many with amazingly high level of strucrural and
  functional complexity
• Life cycles
• Asexual reproduction common
• Sexual reproduction may occur when conditions
  deteriorate
• Some life cycles simple, many extremely complex

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Origin of the Eukaryotic Cell
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Ecology of Protists

• Protists are of enormous eco-logical importance
• Photoautotrophic forms
• Produce oxygen
• Function as producers in both freshwater and
  saltwater ecosystems
• Major component of plankton
• Organisms that are suspended in the water
• Serve as food for heterotrophic protists and
  animals
• Many protists are symbionts
• Ranges from strict parasitism to mutualism
• Coral reefs greatly aided by symbiotic
  photoautotrophic protists in tissues of corals

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Evolution of Protists

• Complexity and diversity of protists makes them
  difficult to classify
• Many classification schemes proposed
• None has broad support
• Cannot be classified as plants, animals, or fungi
• Could be split into as many as a dozen kingdoms
• The scheme chosen for this discussion is based on
  modes of nutrition

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Protist Diversity
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Diversity of ProtistsGreen Algae The
Chlorophyta

• Phylum Chlorophyta
• Approximately 7,500 species
• Inhabit a variety of environments including
  oceans, freshwater, snowbanks, tree bark, and
  turtles backs
• Many are symbionts with fungi, plants, or animals
• Morphology varied
• Majority unicellular, but many are filamentous or
  colonial
• Some are multicellular and resemble leaves of
  lettuce
• Plants thought to be derived from Chlorophyta
  because both groups
• Have a cell wall that contains cellulose
• Possess chlorophylls a and b, and
• Store excess food as starch

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Green AlgaeChlamydomonas

• A minute (lt25 µ m), actively moving flagellate
• Inhabits still, freshwater pools
• Fossil ancestors date back over a billion years
• Anatomy
• Definite cell wall
• Single, large, cup-shaped chloroplast
• Chloroplast with a pyrenoid where starch is
  synthesized
• Many with a bright red eyespot, or stigma on
  chloroplast
• Two long, whip-like flagella
• Project from the anterior end
• Operate with a breaststroke motion

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Electron Micrograph of Chlamydomonas
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Green AlgaeChlamydomonas

• Most often reproduces asexually
• As many as 16 daughter cells within parent cell
• Escape by digesting the parent cell
• Occasionally reproduces sexually
• Gametes fuse to form a zygote
• Becomes a heavy-walled, resistant zygospore
• Goes into a period of dormancy
• Upon germination produces four zoospores by
  meiosis
• Spore - a reproductive cell that develops into
  a new organism without fusing with another cell
• Zoospore - flagellated spores, typical of
  aquatic species

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Reproduction in Chlamydomonas
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Green AlgaeSpirogyra

• Filamentous green algae
• Found in green masses on the surfaces of ponds
  and streams
• Has ribbon-like, spiraled chloroplasts
• Sexual reproduction by conjugation
• A temporary union during which the cells exchange
  genetic material
• Two filaments line up parallel to each other
• Cell contents of one filament move into the cells
  of the other filament
• Forms diploid zygospores
• In spring, undergo meiosis to produce new haploid
  filaments

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Spirogyra
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Green AlgaeMulticellular Forms

• Ulva
• Multicellular green alga
• Commonly called sea lettuce
• Thallus (body) is two cells thick
• Can be as much as a meter long
• Sexual cycle involves alternation of generations
• Similar to higher plants, except
• Both generations look exactly alike, and
• The gametes all look the same

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Multicellular Green Algae
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Green AlgaeColonial Forms

• Volvox
• A colony is a loose association of independent
  cells
• A Volvox colony
• A hollow sphere
• Thousands of cells arranged in a single layer
  surrounding a watery interior
• Each cell of colony resembles a Chlamydomonas
  cell
• Flagella beat in a coordinated fashion
• Some cells are specialized for reproduction
• Each can divide asexually to form a new daughter
  colony within the parental colony
• Leaves parental colony by releasing an enzyme
  that dissolves away a portion of the parental
  colony

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Volvox
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Diversity of ProtistsRed Algae The Rhodophyta

• Multicellular
• About 5,000 species
• Live mostly in warmer seawater, some as deep as
  200 m
• Economic Importance
• Agar - capsules dental impressions cosmetics
  culture medium electrophoresis food prep.
• Carrageen - an emulsifying agent used in
  chocolate, low-fat foods, cosmetics
• The reddish-black wrappings around sushi rolls
  consist of processed Porphyra blades

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Red Algae
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Diversity of ProtistsBrown Algae The
Phaeophyta

• About 1,500 species
• Most live in colder ocean waters along rocky
  coasts
• No unicellular or colonial brown forms
• Morphology
• Some small forms with simple filaments
• Others large multicellular forms that may exceed
  200 m in length
• Pigments
• Chlorophylls a and c
• Fucoxanthin (a type of carotinoid pigment) gives
  them their color
• Excess food stored as a carbohydrate called
  laminarin

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Brown Algae
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The Phaeophyta

• Multicellular forms of green, red, and brown
  algae are called seaweeds
• Laminaria (a kelp), and Fucus, (rockweed), are
  common intertidal seaweeds
• Nereocystis and Macrocystis often form
  forest-like thickets in deeper waters
• Sargassum forms floating masses where other
  organisms find shelter
• Harvested for food and fertilizer
• Macrocystis is source of algin, a thickener for
  foods

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The Phaeophyta

• Laminaria shows tissue differentiation
• Transport organic nutrients in a tissue
  resembling phloem
• Life cycle
• Most brown algae have alternation of generations
• In some species of Fucus
• Meiosis produces gametes instead of spores
• The adult is always diploid, as in animals

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Diversity of ProtistsYellow-green Algae The
Chrysophyta

• Diatoms (formerly Bacillariophyta) are the most
  numerous unicellular algae in the oceans
• Significant portion of phytoplankton
• Cell wall
• Two valves, with the larger valve acting as a lid
  (like a mint tin)
• Contains silica
• Diatomaceous earth used as
• Filtering agents
• Sound-proofing materials
• Polishing abrasives

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Diversity of ProtistsDinoflagellates The
Pyrrophyta

• About 4,000 species of unicellular aquatic and
  marine organisms
• Morphology
• Cell is usually bounded by protective cellulose
  plates impregnated with silicates
• Typically with two flagella
• One in a longitudinal groove with its distal end
  free
• The other lies in a transverse groove that
  encircles the organism
• Symbiotic dinoflagellates in corals called
  zooxanthellae
• Dinoflagellates provide their host with organic
  nutrients
• Corals provide wastes that fertilize the algae
• Some lack chloroplasts and are parasitic
• Gymnodinium brevis may cause red tide
• Produce a powerful neurotoxin that has caused
  massive fish kills
• Consume shellfish during outbreak can cause
  respiratory paralysis

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Diatoms and Dinoflagellates
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Fish Kill and Dinoflagellate Bloom
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Diversity of ProtistsThe Euglenoids Phylum
Euglenophyta

• Small freshwater unicellular organisms
• Difficult to classify
• Have two flagella and an eyespot (shades a
  photoreceptor)
• One flagellum much longer than the other
• Projects out of an anterior, vase-shaped
  invagination
• Called a tinsel flagellum because of hair-like
  projections
• Cell bounded by flexible pellicle
• Chloroplasts
• Surrounded by three rather than two membranes
• With a pyrenoid which produces an unusual type of
  carbohydrate called paramylon

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Euglena
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Diversity of ProtistsZooflagellates Phylum
Zoomastigophora

• Colorless heterotrophs
• Most symbiotic and many parasitic
• Well known for causing various diseases in humans
• Trypanosoma
• African sleeping sickness - Tsetse fly
• Chagas disease Kissing bug
• Giardia lamblia
• Most common flagellate in human digestive tract
• Causes severe diarrhea
• Cysts are transmitted in contaminated water
• Beavers are important reservoir hosts
• Trichomonas vaginalis
• Sexually transmitted protist,
• Infects urogenital organs a common cause of
  vaginitis

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Zooflagellates
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Giardia lamblia
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Diversity of ProtistsProtists with Pseudopods

• Pseudopods form when cytoplasm streams forward in
  a particular direction
• Amoeboids (phylum Rhizopoda) are protists that
  move and ingest their food with pseudopods
• Phagocytize food
• Entamoeba histolytica - a parasite of the human
  colon
• Causes amoebic dysentery
• Can be fatal
• Foraminiferans (phylum Foraminifera) and
  radiolarians (phlyum Actinopoda)
• Both have a skeleton (test) of either calcite or
  silica

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Protists with Pseudopods
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Diversity of ProtistsThe Ciliates Phylum
Ciliophora

• Ciliates (phylum Ciliophora) are among the most
  complex of the protozoans
• Hundreds of cilia beat in coordinated rhythm
• Most are holozoic, swallowing food whole
• Divide by transverse binary fission during
  asexual reproduction
• Two nuclei of differing types
• Micronucleus Heredity
• Macronucleus Metabolism

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Ciliates
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Diversity of ProtistsThe Sporozoans Phylum
Apicomplexa

• Nonmotile obligate parasites
• Most serious parasitic disease of human is
  malaria
• Plasmodium spp
• Kills 3,000,000 people each year
• Transmitted by mosquito
• Toxoplasma
• Humans get from cats
• Causes birth defects and mental retardation when
  pregnant mom exposed

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Life Cycle of Plasmodium vivax
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Diversity of ProtistsSlime Molds

• Plasmodial Slime Molds - Phylum Myxomycota
• Body in the form of a plasmodium
• Diploid, multinucleated, cytoplasmic mass
• Enveloped by a slimy sheath
• Eventually produces sporangium which in turn
  produces spores
• Cellular Slime Mold - Phylum Acrasiomycota
• Body in the form of individual amoeboid cells
• Later aggregate into pseudoplasmodium which then
  forms sporangium spores

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Plasmodial Slime Molds
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Diversity of ProtistsWater Molds - Phylum
Oomycota

• Most live in the water
• Phylum name refers to the enlarged tips (called
  oogonia) where eggs are produced
• Body filamentous, appearing like true Fungi
• Cell walls largely of cellulose rather than
  chitin
• The organism is diploid (not haploid as in the
  fungi)
• Phytophthora infestans caused the 1840s potato
  famine in Ireland
• Saprolegnia is often seen as a white, cotton-like
  coating on dead aquarium fish

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Water Mold
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Review

• Protist Biology
• Protist Evolution
• Protist Diversity
• Green Algae
• Red Algae
• Brown Algae
• Diatoms
• Dinoflagellates

• Protist Diversity, cont.
• Euglenoids
• Zooflagellates
• Pseudopods
• Ciliates
• Sporozoans
• Slime Molds
• Water Molds

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