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Chapter 28: the ProtistsEven a low-power microscope can reveal a great variety of organisms in a drop of pond waterThese amazing organisms belong to the diverse kingdoms of mostly single-celled eukaryotes informally known as protistsAdvances in eukaryotic systematics have caused the classification of protists to change significantly

Kingdom Protista??now part of the Domain Eukaryotaeukaryotes = true nucleusevolution of a nucleus for the genetic informationevolution of membrane-bound organellesdiverse group of single and colonial forms informally known as The Protistsbut Kingdom Protista really doesnt exist anymore too polyphyleticprobably arose from more than one prokaryotic group7 to 45 species recognized depending on zoologistProtistsinclude groups that are photoautotrophs, heterotrophs and mixotrophsmixotrophs = combine photosynthesis and heterotrophic nutritiondivide the protists into three categories:1. Photosynthetic plant-like or algae2. Ingestive animal-like or protozoansamoeba3. Absorptive fungus-like

Cellular Anatomymost are unicellularbut the cellular composition is extremely complexunicellular protists carry out similar functions to multi-cellular eukaryotes with their organ systemsdo so using subcellular organellesmany of these organelles are seen in higher organismsother organelles are not found in the typical multicellular eukaryotecontractile vacuoles for osmoregulation

Protist Evolutiondiversity of protists has its origins in endosymbiosisprocess where a unicellular organism engulfs another cell become endosymbionts and eventually a new organellee.g. acquisition of mitochondria ingestion by alpha-proteobacteria by an ancestral cellEndosymbiosisearly cellular evolution ingestion of a photosynthetic cyanobacteria through primary endosymbiosis by a primitive eukaryoteeventual development into the plastids of the photosynthetic red and green algae

Red and green algae then underwent secondary endosymbiosisthey themselves were ingested by another primitive eukaryotic cell to eventually become the plastids of the protists listed below in the figure

CyanobacteriumPrimaryendosymbiosisSecondaryendosymbiosisSecondaryendosymbiosisSecondaryendosymbiosisHeterotrophiceukaryoteRed algaeGreen algaeDinoflagellatesPlastidApicomplexansStramenopilesPlastidEuglenidsChlorarachniophytesThe 5 Supergroups of EukaryotesPhylogenetic classification of eukaryotes produces five Clades:1. Excavata2. Chromalveolatacommon ancestors the alveolates and stramenophiles3. Rhizaria4. Archaeplastidacontains green algae and land plants5. Unikontaslime molds, entamoebas, fungi and animalsEukaryotic Phylogenetic Tree

AlveolataDiplomonadidaParabasalaEuglenozoaAncestral eukaryoteStramenopilaAmoebozoa(Opisthokonta)(Viridiplantae)CercozoaRadiolariaRhodophytaPlantsChlorophytesCharophyceansRed algaeMetazoansFungiChoanoflagellatesCellular slime moldsPlasmodial slime moldsGymnamoebasEntamoebasRadiolariansChlorarachniophytesForaminiferansBrown algaeGolden algaeOomycetesDiatomsCiliatesApicomplexansEuglenidsDinoflagellatesKinetoplastidsDiplomonadsParabasalidsExcavataChromalveolataUnikontaRhizariaArchaeplastidaAnimaliaChlorophytaFungiPlantaeCharophytaClade:Clade: Excavata

A. DiplomonadsB. Parabasalids C. Euglenozoans

Clade: Excavata

Diplomonads & Parabasilids protists in these two groups lack plastids (no photosynthesis) mitochondria do not have DNA or the enzymes for the citric acid cycle or proteins for the electron transport chainanaerobic environmentsClade: ExcavataA. Diplomonadstwo equal-sized nuclei and multiple flagellaflagella is very different from prokaryotic flagellahave modified mitochondria = mitosomesmany are parasites

giardia intestinalis B. Parabasalidsalso have reduced/modified mitochondriainclude the protists called trichomonads Trichomonas vaginalis mobility through an undulating membrane in addition to flagella

LE 28-5bFlagellaTrichomonas vaginalis, a parabasalid (colorized SEM)Undulating membrane5 mC. Euglenozoansbelong to a diverse clade includes heterotrophs, photosynthetic autotrophs and parasitesconsidered a photosynthetic protist similar to algaelike algae the photosynthetic protists have chlorophyll a and b in chloroplastsdistinguishing feature a rod with either a spiral or crystalline structure inside each of their flagella

divided into the groups: 1. the Kinetoplastids 2. the Euglenoids

Crystalline rodFlagella (9+2 arrangement)Cross-section of a Euglenozoan1. Kinetoplastids - Trypanosomesdefined by a single, large mitochondrion that contains an organized mass of DNA = kinetoplastfree-living forms in freshwater, marine and soil feed on the prokaryotes in these ecosystemssome are parasites of animals, plants and other protistsTrypanosoma gambienese sleeping sickness (neurological disease) & Chagas disease (congestive heart failure) in humans

Kinetoplastids: Trypanosoma

Life cycle-cycles between the tse tse fly and the human-different forms of the trypanosome depending on what host (fly vs. human) and where it is in the host

fly injects the trypanosomemultiplication in the human host e.g. in the bloodbit by fly and transfer back to flymultiplication in the flys gut and then in the salivary gland

unicellular protist most are autotrophicseveral chloroplasts with chlorophyll a and b and carotenoid pigmentsmain characteristic - two flagella that emerge from a pocket structureat the pocket is a large contractile vacuole that connects to the outsidecontinuously collects water from the cell and returns it to the outside regulates osmotic pressuretwo flagella arise at this reservoirthe long one emerges from the canal and actively beats for locomotion

2. Euglenoids The Euglenaused to be classified as the Class Phytomastigophoreainside the plasma membrane is a structure called the pelliclearticulated strips of protein lying side by side that enable turning and flexing of the protisteyespot (stigma) - near the flagellaallows only certain wavelengths of light to strike the light detectorlight detector (photoreceptor) detects the filtered light and results in movement toward the light direction

2. EuglenoidsClade: Chromalveolataoriginated more than a billion years ago when their ancestor ingested a photosynthetic red algae (via secondary endosymbiosis)plastids within these protists have red algae origins (DNA analysis)divided into two major groups: 1. Alveolates 2. StramenophilesClade: ChromalveolataA. Alveolates:1. Dinoflagellates2. Apicomplexans3. CiliatesB. Stramenophiles1. Diatoms2. Golden Algae3. Brown Algae4. OomycetesChromalveolata - A. Alveolatescharacterized by membrane-bound sacs called alveolijust under the plasma membranefunction unknown

1. Dinoflagellates move through flagellar action2. Apicomplexans - parasites3. Ciliates move through ciliary action

Alveolates: 1. Dinoflagellatesseveral thousand speciesdinos = whirlingsurrounded by a cell wall encrusted with silica - act as armormost are autotrophic with well-formed plastids for photosynthesispossess mitochondria with tubular cristae (similar to animals)two flagellae located in groovesone groove is transverse (around the protist) = cingulum its flagella propels the dinoflagellate forward and causes it to spinother groove is perpendicular to that = sulcus the flagella acts as the rudder

LE 28-103 mFlagella

capable of proliferating explosively blooms red tide (carotenoid pigments found in the plastids) dinoflagellates produce a toxin that kills off invertebratessome can be bioluminescent ATP driven reaction that creates a glow at night

Alveolates: 2. Apicomplexansnearly all are animal parasitesspread through the formation of tiny infectious cells = sporozoitesnamed because one end (apex) contains a complex of organelles specialized for penetrating host tissues and cellshave a non-photosynthetic plastid = apicoplast which has many functions including the synthesis of fatty acids for its membraneslife cycle includes sexual and asexual stagesrequires more than one host to complete

Alveolates: 2. Apicomplexansbest known is the Plasmodium causes malariarivals tuberculosis as the leading cause of human death by infectious diseasecan be reduced by insecticides that kill the Anopheles mosquito (DDT) and by drugs that kill the Plasmodium (quinine based drugs)vaccines hard to develop Plasmodium lives inside the RBC (hidden)carriers of sickle cell anemia gene resistant to malaria

gametocyte

trophozoitesPlasmodium Life Cycle1. infected Anopheles mosquito bites a person injecting its sporozoites (n)2. sporozoites enter the liver and undergo division to become merozoites (n)3. the merozoites infect RBCs via their apical complex4. merozoites develop into gametocytes which break out of the RBCsfevers and chills5. gametocytes picked up by a new mosquito6. gametes form and fertilization takes place in the mosquitos digestive tract zygote7. an oocyst develops and produces more sporozoites which are delivered to the human when bitten again

LE 28-11Sporozoites(n)Inside mosquitoOocystZygote(2n)MEIOSISMerozoite(n)LivercellLiverFERTILIZATIONGametesGametocytes(n)Red bloodcellsInside humanMerozoiteApexRed bloodcell0.5 mHaploid (n)KeyDiploid (2n)Alveolates: 3. Ciliates - Parameciumuse of cilia to move and feedcilia may completely cover the protist or may cluster in a few rows or tuftsdistinguished by the presence of two types of nuclei: macronucleus (large) and micronucleus (small)may have one or more of each typemacronucleus contains dozens of copies of the genomecontrol the everyday functions of the ciliatemicronucleus function in reproductionexchanged between two ciliates during conjugationLE 28-12

FEEDING, WASTE REMOVAL, AND WATER BALANCEContractilevacuoleOral grooveCell mouthMicronucleusMacronucleus50 mThousands of cilia cover thesurface of Paramecium.Paramecium, like other freshwater protists, constantly takes in water by osmosis from the hypotonic environment. Bladderlike contractile vacuoles accumulate excess water from radial canals and periodically expel it through the plasma membrane.Paramecium feeds mainly on bacteria. Rows of cilia along a funnel-shaped oral groove move food into the cell mouth, where the food is engulfed into food vacuoles by phagocytosis.Food vacuoles combine with lysosomes. As the food is digested, the vacuoles follow a looping path through the cell.The undigested contents of food vacuoles are released when the vacuoles fuse with a specialized region of the plasma membrane that functions as an anal pore.Parameciumfreshwater protist constantly takes on water from its hypotonic environmentthey contain contractile vacuoles for the regulation of osmotic pressure accumulate excess water and then expel it through the plasma membrane back into the environmentcilia participate in movementbut also gather food and move it toward the oral groove which holds the cell mouth at the bottomfood is then engulfed into a food vacuole via phagocytosisfood vacuoles combine with lysosomes containing digestive enzymes

FEEDING, WASTE REMOVAL, AND WATER BALANCEContractilevacuoleOral grooveCell mouthMicronucleusMacronucleus50 mThousands of cilia cover thesurface of Paramecium.Paramecium, like other freshwater protists, constantly takes in water by osmosis from the hypotonic environment. Bladderlike contractile vacuoles accumulate excess water from radial canals and periodically expel it through the plasma membrane.Paramecium feeds mainly on bacteria. Rows of cilia along a funnel-shaped oral groove move food into the cell mouth, where the food is engulfed into food vacuoles by phagocytosis.Food vacuoles combine with lysosomes. As the food is digested, the vacuoles follow a looping path through the cell.The undigested contents of food vacuoles are released when the vacuoles fuse with a specialized region of the plasma membrane that functions as an anal pore.ParameciumParameciumasexual reproduction through binary fissionsexual reproduction involves conjugation1. two compatible mating strains align side by side and partially fuse 2. meiosis of their micronuclei produces a total of 4 haploid micronuclei in each cell3. three micronuclei in each disintegrate & the remaining micronuclei in each divides by mitosis- resulting in 2 micronuclei in each paramecium4. the cells swap one of their micronuclei genetic recombination 5. the cells separate

CONJUGATION AND REPRODUCTIONMEIOSISMICRONUCLEARFUSIONHaploidmicronucleusDiploidmicronucleusDiploidmicronucleusCompatiblemates Two cells of compatible mating strains align side by side and partially fuse.Macronucleus Meiosis of micronuclei produces four haploid micronuclei in each cell. Three micronuclei in each cell disintegrate. The remaining micro-nucleus in each cell divides by mitosis. The cells swap one micronucleus. The cells separate.Key Micronuclei fuse, forming a diploid micronucleus.ConjugationReproduction Two rounds of cytokinesis partition one maccronucleus and one macronucleus into each of four daughter cells. The original macronucleus disintegrates. Four micronuclei become macronuclei, while the other four remain micronuclei. Three rounds of mitosis without cytokinesis produce eight micronuclei.Paramecium

CONJUGATION AND REPRODUCTIONMEIOSISMICRONUCLEARFUSIONHaploidmicronucleusDiploidmicronucleusDiploidmicronucleusCompatiblemates Two cells of compatible mating strains align side by side and partially fuse.Macronucleus Meiosis of micronuclei produces four haploid micronuclei in each cell. Three micronuclei in each cell disintegrate. The remaining micro-nucleus in each cell divides by mitosis. The cells swap one micronucleus. The cells separate.Key Micronuclei fuse, forming a diploid micronucleus.ConjugationReproduction Two rounds of cytokinesis partition one maccronucleus and one macronucleus into each of four daughter cells. The original macronucleus disintegrates. Four micronuclei become macronuclei, while the other four remain micronuclei. Three rounds of mitosis without cytokinesis produce eight micronuclei.6. the two micronuclei in each cell fuse to produce a diploid nuclei7. three round of mitosis without fission results in 8 micronuclei in each paramecium8. the original macronuclei disintegrates and 4 micronuclei become 4 macronuclei to replace it leaves 4 micronuclei9. two rounds of binary fission now happen results in 4 daughter cells10. the micronuclei (4) and macronuclei (4) then partition into the four daughter cells each paramecium ends up with 1 micronuclei and 1 macronuclei

Got all that??

CONJUGATION AND REPRODUCTIONMEIOSISMICRONUCLEARFUSIONHaploidmicronucleusDiploidmicronucleusDiploidmicronucleusCompatiblemates Two cells of compatible mating strains align side by side and partially fuse.Macronucleus Meiosis of micronuclei produces four haploid micronuclei in each cell. Three micronuclei in each cell disintegrate. The remaining micro-nucleus in each cell divides by mitosis. The cells swap one micronucleus. The cells separate.Key Micronuclei fuse, forming a diploid micronucleus.ConjugationReproduction Two rounds of cytokinesis partition one macronucleus and one macronucleus into each of four daughter cells. The original macronucleus disintegrates. Four micronuclei become macronuclei, while the other four remain micronuclei. Three rounds of mitosis without cytokinesis produce eight micronuclei.-partially fuse-1 micronucleus becomes 4 via meiosis (haploid)-3 disappear-1 micronuclei becomes 2 via mitosis-paramecia swap 1 micronuclei and separate-fuse 2 micronuclei into 1 (diploid)-micronucleus becomes 8 (mitosis/no cytokinesis)-macronucleus disappears-so 4 of the 8 micronuclei develop into 4 macronuclei-4 of the micronuclei stay micronuclei-2 rounds binary fission 4 daughter paramecia-each daughter cell gets a macronuclei and a micronuclei

Chromalveolata - B. Stramenophilesstramen = straw; pilos haircontains several groups of phototrophs (considered to be algae)flagella are said to be hairy this hairy flagellum is paired with a smooth flagellum1. oomycetes water molds2. bacillariophytes - diatoms3. chrysophytes golden algae4. phyophyceans brown algae

SmoothflagellumHairyflagellum5 mFirst of All - What is Algae??photosynthetic protistsalgae = eukaryotic organism with chlorophyll a pigments that carry out oxygen-producing photosynthesisstudy of algae = phycologyno longer any formal classification schemesalgae are scattered across many phyla = polyphyleticBUT they differ from plants lack a well-organized vascular system and they have a simple reproductive systemoccur most often in waterfresh and marine may be suspended as planktonic organisms or attached to the bottom (benthic)Algae: Photosynthetic Protistsalgae frequently confused with planktonplankton = free-floating microscopic aquatic organismsphytoplankton made up of algae and small plantszooplankton non-photosynthetic protists and animalsclassical algae are now grouped together with the plants - Phylum Chlorophyta some are a separate lineage - known as red algaePhylum Rhodophytasome are grouped with the stramenophiles - yellow and brown algaePhyla Chrysophyta and Phaeophytaimportant properties that classify them:1. cell wall composition rigid cell wall of cellulose2. the form in which food is stored3. chlorophyll molecules and accessory pigments (carotenoids)4. flagella number and location of their insertion into the cell5 morphology of the cells and/or body comprised of a vegetative body = thallus6. habitat: marine or freshwater7. reproductive structures: reproduction is asexual or sexual8. mitochondria cristae structure: tubular, disc or plate-like (lamellar)

Algae: Photosynthetic ProtistsStramenophiles: 1. Oomycetes: Water molds

water moldoomycete = egg funguswater molds, white rusts and downey mildewsused to be considered fungi have multinucleate filaments called hyphae that resemble those seen in fungimolecular data also cannot confirm fungal originsdo not carry out photosynthesis non-autotrophicacquire nutrients as decomposers grow as cottony masses on dead animals and algae = heterotrophic

Stramenophiles: 2. Diatoms

100,000 species of unicellular algae surrounded by unique glass-like wall made of silica embedded in an organic matrixtwo parts that overlap like a shoe box and lidupperlid = epitheca, lowerlid = hypothecaeffective protection against extreme crushing forcesreproduce asexually via mitosisdaughter receives half of the parental cell wall and generates a new halfmost are photosynthetic chlorophylls a and c and carotenoids

Stramenophiles: 2. Diatomsmajor component of phytoplankton in fresh and marine environments in cooler waterssource of food for fish and other marine animalsupon death sink to the bottom = diatomaceous earthactive ingredient in detergents, fine abrasive polishes, paint removers, decoloring oils, filtering agents, components of insulation and soundproofing products, reflective paint additive

Stramenophiles: 3. Golden Algae -Phylum Chrysophytaall species are photosynthetic photosynthetic pigments: chlorophylls a and c + carotenoids found in plastids (like plants)dominant pigment is a carotenoid called fucoxanthin golden-brown colormost are unicellular but some are colonial most are biflagellated both attached near one end of the cell

DinobryonStramenophiles: 4. Brown algae - Phylum Phaeophytabrown algae most complex algaeall are multicellular and all are marinehave the most complex multicellular anatomy of all algaesome have specialized tissues like animals and plantsinclude the seaweedsgiant seaweeds in intertidal zones kelps

4. Brown algae: Phaeophytabrown algae composed of a thallus = algal body that is plant-likethallus has a rootlike hold-fast which anchors the seaweed and a stem-like stipe that supports leaf-like bladesBUT there are no true roots, stems and leaves!blades surface for photosynthesisblades can come equipped with floats to keep them near the surface

LE 28-18BladeStipeHoldfastBrown algae ThallusBrown algae: Life cycle

DevelopingsporophyteZygote(2n)FERTILIZATIONMature femalegametophyte(n)EggSpermMEIOSISHaploid (n)KeyDiploid (2n)SporangiaSporophyte(2n)ZoosporesFemaleGametophytes(n)Malee.g. LaminariaAn overview of Alternation of Generationsthe spores develop into gametophytes (n)the gametophytes make gametes (n)the gametes fuse and regenerate the diploid sporophyte (2n)brown algae exhibit alternation of generationsalternate between haploid and diploid multicellular formsonly applies to multicellular stages in the life cycletwo forms seen that are structurally different:A. diploid sporophyte for the production of haploid spores via meiosisB. haploid gametophytes for the production of haploid gametes via mitosis

Brown algae: Life cycle

DevelopingsporophyteZygote(2n)FERTILIZATIONMature femalegametophyte(n)EggSpermMEIOSISHaploid (n)KeyDiploid (2n)SporangiaSporophyte(2n)ZoosporesFemaleGametophytes(n)Malee.g. Laminarialife cycle starts with the diploid sporophyte (adult algae thallus)1. on the blade of the sporophyte development of a sporangium2. the diploid sporangium develops haploid zoospores by meiosis 3. 50% of zoospores develop into male gametophytes and 50% into female gametophytes (small but multicellular)4. the haploid gametophytes produce haploid gametes via mitosis 5. gametes are released and fuse to form the diploid zygote6. zygote develops into a new sporophyte which grows via mitosis to form a new adult algae

Clade Rhizariacharacterized by the presence of threadlike pseudopodia = extensions of the cytoplasm that bulge anywhere along the cells surfacefalse feetused in locomotion and prey captureextend and contract pseudopodium by assembly and disassembly of actin subunits into microfilaments locomotion: anchor a tip to the surface stream cytoplasm into the pseudopodium prey capture: pseudopodia senses the prey through physical contact and surrounds it

members of this clade:A. RadiolarinsB. ForamsC. Cercozoans

Clade RhizariaA. Radiolarians: delicate, intricately symmetrical internal skeletons made of silicaaxiopodia which radiate out from a central body reinforced by microtubultespseudopodia are also capable of phagocytosing food cytoplasmic streaming then carries the food into the central body

LE 28-23200 mPseudopodiaRadiolarinsClade RhizariaB. Forams: formerly called foraminiferansnamed for their porous shells holes in the shells are called foraminashell is called a test = single piece of organic material hardened with calcium carbonatepseudopodia extend through the holes function in swimming, in making the test and feeding

ForamsC. Cercozoans: The Amoebacontain the organisms called amoebaeamoeba species are also found in other cladesmost are heterotrophs many are parasites of plants and animalssome can be predators!predators of bacteria

A word about amoebasno longer one specific cladetoo polyphyleticfind amoebas in several clades 2 major ones:CercozoaAmoebozoaamoeba = protist that does not have a definitive shapeeat via phagocytosishave an outer ectoplasm and an inner endoplasmmove by pseudopodia that form through cytoplasmic streaming of their ectoplasm and endoplasm

Clade Archaeplastidamore than a billion years ago heterotrophic protist acquired a cynanobacterial endosymbiontgave rise to red algae and green algaethese cyanobacteria evolved into plastidsnumerous functions: photosynthesis and storage475 million years ago green algae ancestors evolved into land plantsred algae, green algae and land plants are now placed into the same clade based on molecular data Archaeplastida

CyanobacteriumPrimaryendosymbiosisHeterotrophiceukaryoteRed algaeGreen algaePlastidPlastid49Clade ArchaeplastidaArchaeplastida can be divided into:A. Red algae Phylum RhodophytaB. Green algae Phylum ChlorophytaC. Charophytes includes Plants; Phylum CharophytaArchaeplastida - A. Red Algae: Phylum Rhodophytared algae 6000 speciesmulticellular algaemost are autotrophic plastids for photosynthesisred pigment = phycoerythritin and blue pigment = phycocyanin (phycobilins)pigments allow for the absorption of green and blue light which have long wavelengths and can penetrate the deeper waters where the red algae are found

red algae 6000 speciessugar storage form = florideancell wall includes a matrix of proteins and sugarsthis matrix is also called agar = polymers of galactoselargest red algae are included in a group called seaweeds (e.g. nori)life cycle does not include a flagellated step must rely on ocean currents to deliver gametes for fertilization

Archaeplastida - A. Red Algae: Phylum RhodophytaArchaeplastida - B. Green algae: Phylum Chlorophytagreen algaenamed for the green chloroplasts contain chlorophyll pigments that are very similar to plantschloroplasts also have a similar structure to plantsthylakoid membranesdivide into two groups:1. Charophytes most closely related to plants2. Chlorophytes 7000 species of green algae

Archaeplastida - B. Green algae: Phylum Chlorophytagreen algae2. Chlorophytes 7000 specieschloro = greenmostly freshwaterchlorophylls a and b + carotenoid pigmentssugar storage form = starchcell walls made of cellulosemost are unicellular some are colonialsome are also multicellular - filamentous (pond scum) and sheet-like formscan also live symbiotically with fungus as lichens

Unicellular Green Algae

e.g. Chlamydomonas example of a unicellular algae two flagella of equal length at the anterior endone conspicuous pyrenoidorganelle found in or beside the chloroplasts of algaeinvolved in carbohydrate synthesis eyespot or stigmamovement towards lighttwo small contractile vacuoles at the base of the flagella function as osmoregulatory organsasexual reproductionsexual reproduction is also possible cell division produces gametes of each sex

Green algae: Life Cycle

MEIOSISHaploid (n)KeyDiploid (2n)SYNGAMYSEXUALREPRODUCTIONZoosporesASEXUALREPRODUCTIONMature cell(n)Zygote(2n)Regionsof singlechloroplastNucleusFlagellaCell wall1 mlife cycle: sexual and asexual stagesmature green algae cells are haploid and have 2 flagellaeasexual reproduction: the algae reabsorbs its flagellae and divides by mitosis to form four identical haploid cells (zoospores) - held within a capsulezoospores are released new mature green algae

MEIOSISHaploid (n)KeyDiploid (2n)SYNGAMYSEXUALREPRODUCTIONZoosporesASEXUALREPRODUCTIONMature cell(n)Zygote(2n)Regionsof singlechloroplastNucleusFlagellaCell wall1 msexual reproduction: happens upon shortage of nutrients haploid algae develops into male and female gametesfusion zygote (diploid + 4 flagella)zygote loses its flagellae and surrounds itself by a coat to protect itselfmeiosis in the zygote results in 4 haploid cells two from each mating typethese released haploid cells become new mature algal cellsGreen algae: Life CycleColonial Green Algaenot really multicellularcolony of unicellular algaee.g. Volvoxcolony or 500 to 60,000 cells mostly small vegetative cellsindividual cells resemble Chlamydomonas bi-flagellatedcells have eyespots will orient toward the lightsome cells are reproductive - develop from the cells at the equator = called gonads gametes for fertilizationzygote undergoes mitosis to form a small daughter colonythe daughter colony remains in the parental colony until it bursts free

Volvox, a colonial freshwater chlorophyte. The colony is a hollow ball whose wall is composed of hundreds or thousands of biflagellated cells embedded in a gelatinous matrix. The cells are usually connected by strands of cytoplasm; if isolated, these cells cannot reproduce. The large colonies seen here will eventually release the small daughter colonies within them.Clade Unikontarecently proposed cladesupergroup of eukaryotes that includes animals, fungi and some protistsmeans one flagellatwo major clades:A. Amoebozoans: the amoebas & slime moldsB. Opisthokonts: fungi and animals

Unikonta: A. Amoebozoans

three types of Amoebozoans:1. Gymnamoebasunicellular, one flagellasoil, freshwater and marinemost are heterotrophic consume bacteria and other protists plus detritus (decomposers)2. Entamoebasparasitic amoebaeinfect all classes of vertebrates and some invertebrateshumans are host to at least 6 speciesEntamoeba histolytica amoebic dysenterythird leading cause of death in the world due to parasites 100,000 deaths each year

3. Mycetezoans = Slime moldscellular slime moldsplasmodial slime moldsUnikonta: A. Amoebozoans

Plasmodial slime molds

1 mmMEIOSISHaploid (n)KeyDiploid (2n)Zygote (2n)SYNGAMYFeedingplasmodiumMatureplasmodium(preparing to fruit)YoungsporangiumMaturesporangiumSpores(n)StalkAmoeboid cells(n)GerminatingsporeFlagellated cells(n)brightly pigmented orange or yellownamed for the formation of a feeding stage = plasmodium in the life cyclecapable of moving over a substrate plasmodium very large but still is unicellularsingle cell undergoes mitosis but fails to divide through cytokinesis super-cellfeeding plasmodium lives on organic matter takes in nutrients through phagocytosisPlasmodial slime molds

1 mmMEIOSISHaploid (n)KeyDiploid (2n)Zygote (2n)SYNGAMYFeedingplasmodiumMatureplasmodium(preparing to fruit)YoungsporangiumMaturesporangiumSpores(n)StalkAmoeboid cells(n)GerminatingsporeFlagellated cells(n)mature plasmodium undergoes sexual reproduction when conditions become harshplasmodium develops sporangia via meiosis which release haploid spores (n)germination of the spores takes place in the presence of adequate moistureresults in the production of either amoeboid cells or flagellated cells both are haploidfertilization (syngamy) requires the fusion of the same type of cell i.e. swarm with swarmproduction of the zygote (2n) and development of a new plasmodium formsCellular slime molds600 m

MEIOSISHaploid (n)KeyDiploid (2n)Zygote (2n)SYNGAMYMigratingaggregateEmergingamoebaSEXUALREPRODUCTIONAmoebasSpores(n)Solitary amoebas(feeding stage)ASEXUALREPRODUCTIONFruitingbodiesAggregatedamoebas200 mfeeding stage is a solitary amoeboid form feeding stageengulfs bacteria and yeasts by phagocytosis can undergo asexual or sexual reproductiondetermined by food supplysexual reproduction: takes place in presence of abundant foodtwo haploid amoebas fuse and form the zygote (2n)the zygote engulfs more haploid amoebae to grow larger forms an aggregateaggregate develops fruiting sporangia - releases haploid spores new amoeba cells