Debbra MarcelJP/8544/13 JIB 115 Plant Diversity: Assignment 1 1.Kingdom Protista All organisms with eukaryotic cells are constituted within a superkingdom known asDomainEukaryathatconsistsofKingdomProtista,KingdomPlantae,Kingdom AnimaliaandKingdomFungi.KingdomProtistaisaverylargeanddiversegroupof eukaryoticorganismsthatdonotfitintoanyoftheotherkingdoms.Thiskingdom consideredasaparaphyleticgroupasitdoesnotcontainallthedescendantsofthe commonancestor.Protistsaremainlyaquaticandcanbefoundalmosteverywhere thereiswater,includingoceans,freshwater,dampsoils,inthemoistureofthe atmosphere as well as in the tissues of other organisms.Generally, protists consist of plant-like protists (algae), animal-like protists (protozoa) and fungi-like protists (molds).Amongalltheprotists,algaeareknownastheclosesttotheterrestrialplantsasthis diverse group is believed to be the ancestors of the plant kingdom. Algae(singular,alga)areclassifiedintoabouteightdivisionswhichinclude phylumChlorophyta(thegreenalgae),phylumChromophyta(theyellow-greenalgae, golden-brownalgae,diatomsandbrownalgae),phylumRhodophyta(theredalgae), phylum Euglenophyta (the euglenoids), phylum Dinophyta (the dinoflagellates), phylum Cryptophyta(thecryptomonads),phylumPrymnesiophyta(haptophytes)andphylum Charophyta(thestoneworts).Besidesalgae,othermembersofkingdomProtistaare protozoans(unicellularanimal-likeeukaryotes),sponges(phylumPorifera)andthe fungi-likeprotists;PhylumMyxomycota(theplasmodiumslimemolds),Phylum Dictyosteliomycota (the cellular slime molds) and Phylum Oomycota (the water molds). Like plants, algae posses cells with cell walls even though cell wall chemistry is diverse.Thisgroupofunicellularandmulticellulareukaryotesrangeinsizeand complexity from unicellular planktonic forms to giant kelps.Unlike plants, multicellular algae posses no root and shoot and the vegetative tissue called thallus (plural, thalli) is anatomicallyandmorphologicallysimple.Likeotherprotists,algaearenutritionally diverseandtheirmodeofnutritionincludesphotosynthetic(autotroph),absorptionof foodinsolution/ingestionoffood(heterotroph)oracombinationofboth(mixotroph).Basically,algaearedistinguishedbasedontheirphotosyntheticpigments(typeof chlorophyllandpresence/absenceofaccessorypigmentse.g.phycobilins, Debbra MarcelJP/8544/13 JIB 115 Plant Diversity: Assignment 1 fucoxanthins)andthechemistryofcellwall(cellulose/silica/algin/pectin). Mostalgaearenon-motileandsomeunicellularalgaemayalsohavetheabilityto move by flagella (zooflagellates) or by means of pseudopodia (sarcodinians). Algae life cycles are diverse and complicated which mainly divided into three main types namely zygotic,gameticandsporic.Likeotherprotists,thereproductionofalgaearevary where some are only known to reproduce asexually (e.g mitosis, fragmentation, fission or budding) while others can also reproduce sexually (e.g syngamy, conjugation, sporic meiosis or zygotic meiosis) or at least employ process of fertilization. The table below are the example of algae that commonly found in our environment: Ecologically,protists form a wide range of mutualisticand parasitic relationship that affect their symbiotic partners and many other members of the community. Algae are among the most important producers in aquatic communities and play crucial role inglobalcyclingofcarbonandoxygen.Phytoplanktonforexample,themicroscopic floatingalgaeconstitutebaseofmarinefoodchainwhilethecorallinealgaewhich functionastropicalreefbuildershaveendosymbioticrelationshipwithcoralanimals thus increase the coral growth in ocean.Major groupKey characteristicsExample Chlorophyta (green algae) Unicellular, colonial or filamentous; contain chloro-phyll a & b, carotenoids and starch; asexual reproduction (e.g fragmentation, zoospores or mitosis); sexual reproduction ( e.g conjugation, isogamous, oogamous) Ulothrix, Spirogyra& Oedogonium Phaeophyta (brown algae) Multicellular; contain chlorophyll a & c, carotenoids, fucoxanthin, peridinin, laminarin; reproductive cells have lateral flagella Giant seaweed, Fucus Rhodophyta (red algae) Multicellular; contain red & blue phycobilins, chloro-phyll d, carotenoids, & floridean starch; life cycle involves three types of thalli & non-motile gametes Polysiphonia sp. Chromophyta Unicellular, some colonial; contain chlorophyll a & c, xanthophylls, carotenoids, starch, glassy shell; reproduce asexually by mitosis or sexually by fusionDiatoma, phytoplankton Dinophyta Unicellular; contain chlorophyll a & c, carotenoids, , starch; some cause red tides that kill fish & poison humans dinoflagellates Euglenophyta Unicellular; no rigid cell wall; contain chlorophyll a & b, carotenoids, xanthophylls, eye spot, paramylon (food starch), pellicle; reproduce by cell division Euglena Debbra MarcelJP/8544/13 JIB 115 Plant Diversity: Assignment 1 2.Thedescriptionofisomorphicalternationofgenerationand heteromorphic alternation of generation in the life cycle of plants. Just like animals, plants do form sperm and egg in male and female structures wherebothgametes(reproductivecells)carryhalfofthehereditarymaterialfromthe parentsgenomerespectively.Eventhoughmostplantsdonothaveseparatesexes liketheanimalsdo,plantshavetheabilitytoreproduceeffectivelyduetothe uniquenessoftheirlifecycle,calledalternationsofgenerations.Therearefive generalized steps in the life cycle of land plants where two generations of multicellular stagesarecalledhaploid(n)anddiploid(2n)generationsthatalternatebetweenone another.Thegenerationofgametophyteproducestwosexuallydifferentmaleand female gametes by mitosis respectively which will unite (fertilization/syngamy) and form a diploid zygote. Then, the zygote that formed will develop into a multicellular diploid sporophyte.Whenthesporophytematured,itproduceshaploidsporesbymeiosis. Finally,thesporeswilldevelopintomulticellularhaploidgametophytesandsothe alternation of generations continues. Therefore, both generations are strongly related to one another in the plant life cycle. Copyright Pearson Education, Inc. Publishing as Benjamin Cummings Figure 1: The generalized scheme of alternation of generations MEIOSISFERTILIZATION Diploid multicellular organism (sporophyte) Haploid multicellular organism (gametophyte) Debbra MarcelJP/8544/13 JIB 115 Plant Diversity: Assignment 1 Isomorphic alternation of generations is the alternation of haploid (gametophyte) plantsbearinggameteswithstructurallyidenticalwithdiploid(sporophyte)plants bearing spores and has more than two generations a year. Ulva sp. is among the algae that undergoing isomorphic alternation of generations.Called as sea lettuce, Ulva sp. isbelongstothephylumofChlorophyta(greenalgae),whichisalsoknownasthe ancestor of terrestrial plants.Except for its ploidy, this multicellular isomorphic species has both gametophyte and sporophyte stages that are very similar in morphology (refer Figure 2 a & b). Incontrasttoisomorphicalternationofgeneration,heteromorphic(antithetic) alternationofgenerationisconsistsoftwomulticellularstages(gametophyteand sporophyte) that are structurally different to one another.Species with heteromorphic lifecyclehavealargemulticellularbodyinonegeneration,buthavesmallerbodyin anothergeneration.Therefore,thelifecycleiscalledheteromorphic,meaning differentforms.ThelifecycleofsomealgaelikeLaminariasp.andallterrestrial plantsareconsistofalternationofheteromorphicgenerations.Inmanyseedless plantslikeferns(referfigure3a&b),thegametophyteandsporophytelookvery distinct types of plants, even though they are forms of the same species.Meanwhile, theseedplantsexhibitsporophyteasthefamiliarplantsweseebecausethe gamethophyte stage is very small (mostly microscopic) and seldom to be noticed. Figure 2 a: Ulva gametophyte Figure 2 b: Ulva sporophyte Figure 3 a: Fern gametophyte (n) Figure 3 b: Fern sporophyte (2n) Cluster of sporangia Debbra MarcelJP/8544/13 JIB 115 Plant Diversity: Assignment 1 3.The gametophyte generation and sporophyte generation in mossesMosses is known as the most primitive group of terrestrial plants which included inthebotanicaldivision(phylum)ofsmall,softplantsthataretypically1-10cmtall, althoughsomespeciescangrowupto50cminheight,likeDawsonia.Thesenon-vascularplantsneitherhaveflowersnorseed,ubiquitousandcommonlygrowin clumpsormatsinshadyordamplocations.Mossesbelongtothephylumof Bryophyta,alongwithliverworts(phylumHepatophyta)andhornworts(phylum Anthocerophyta), where all are called as bryophytes or non-tracheophytes due to their lacknessofdistinctivekindofconductivecellscalledtracheid,eventhoughsome mosses do have simple vascular tissue.Like other plants, the life cycle of mosses are characterized by alternation of generations and these plants are known to have closest resemblance of vascular plants.However, like other bryophytes, they are unique from othergroupsofterrestrialplantswherethegametophyteisthemostconspicuous rather than sporophyte generation.Thegametophytestagesofmostmossesaredioecious,withseparate male and female individuals in the population. In mosses, the dominant generation is the leafy haploid (n) form is known as gametophyte, which produce gamete mitotically andknownastheactualplant. Theinitialphaseofgrowthisbyformation of a mass green branched filament of cells called protonema.The stems and leaves of mosses arepartsofgametophyte,notasporophyte,thereforetheyarenothomologouswith those of vascular plants.Rhizoids which is multicellular root-like structures, grow from the underside of protonema, only act as anchor for the stem and not involved in either waterormineralsabsorptionliketherootofvascularplants.Theleafystemcalled gametophoresisthematuregametophyteofmossesthatgrowfromapicalmeristem whichthenproducearchegonia(femalegamete-producingstructure)andantheridia (malegamete-producingstructure)separatelyatthevase-likegametangia(antheridia whichproducesperm,orarchegoniawhichproduceegg)thatappeartobe advantageousonthewaterfromenvironment.Mosseshaveaprimitivemethodof fertilization that involves a motile, biflagellate sperm that swims through water to reach theeggonfemaleplants.Whenmalegametes/spermsmature,antheridiumbreaks open and they move to archegonia to fertilize egg by swimming guided by the secretion Debbra MarcelJP/8544/13 JIB 115 Plant Diversity: Assignment 1 ofsucrosefromarchegonia.Then,fertilizationoccursthereanddiploidzygoteis formed.Ground water not only required to facilitate fertilization of mosses but also to support their growth and therefore mosses always found in the moist environment. Unlike gametophyte, the sporophyte stage of mosses is more like a small flower, whichisparasiticanddependsonthegametophyteforitsnutrients.Sporophyte, which is the diploid generation of the plant, arises after male and female gametophyte mateandfusedtheirhaploidgametes.Theresultingdiploidzygotegrowsinto collection small and long seta (stalk) that will remain attached to and dependent on the long-livegametophyteofmosses.Eachofthestalksbearsacapsule(sporangium) that looks like a salt-shaker at the tip (calyptra), which protects the growing sporophyte and protrudes a certain times in a year.The haploid spores that formed by meiosis in the capsule are casted out from the peristome (the upper part of the capsule) when the capsulebreaksopen,landonthegroundandgerminateintonewgenerationof gametophyte, which is the leafy green mat. Copyright Pearson Education, Inc. Publishing as Benjamin Cummings Fertilization Meiosis Figure 4: The life cycle of mosses Debbra MarcelJP/8544/13 JIB 115 Plant Diversity: Assignment 1 4.Differences between bryophytes as a group from other plants. Theplantkingdomrepresentsanextremelydiversegroupofmostlyterrestrial photosynthetic organisms.This kingdom also known as embryophyta (embryo bearing plant), and all the members share the common derived trait of multicellular, dependent embryo.Embryophyta is consists of ten phyla of terrestrial plants that divided into four maingroupscalledbryophytes,pteridophytes,gymnospermsandangiosperms.The bryophytesincludethreeseparatephylanamelyphylumHepatophyta(liverworts), Anthocerophyta(hornworts)andBryophyta(mosses),thatnamedbasedontheir structures.Theseprimitiveplantsbelievedtoevolvefromgreenalgaeandmayhave the first numerous celled florae to transition to live on land.Pteridophytes, which is a groupofseedlessvascularplants,consistsoftwophyla;phylumLycophyta (lycophytes)andphylumPterophyta(ferns,horsetailsandwhiskferns).Thenaked seed-bearingplantsarebelongtothegroupofgymnosperms,whichconsistoffour phylanamedphylumGinkgophyta(ginkgo),phylumCycadophyta(cycads),phylum Gnetophyta(gnetae)andphylumConiferaphyta(conifers). Themostdiversegroup of plantsbelongstothecladeofangiosperms,meaningtheseeds/spermsoftheplants enclosed with protective chambers and this group is solely placed within the phylum of Antophyta (flowering plants).Generally, most present-day plants have an extensive system of vascular tissue where the cells joined into tubes that transport water and nutrients throughout the plant body.Eventhoughbryophytesdoalsohavecellwallsmadeofcellulose,posses chlorophyll a and b within their chloroplast and have alternation of generations in their life cycle just like thevascular plants, they donot have complexvascular systemand therefore called as non-vascular plants. Meanwhile, the pteridophytes, gymnosperms and angiosperms are all called as vascular plants (tracheophytes) due to the presence of vascular system in their bodies respectively.Bryophytes are usually small and close tothegroundbecausetheseplantslackofcomplexwaterdistribution,thusunableto supportlargegrowthandlimitthesizeoftheplantsastheycannottransportnutrient (waterand food) faragainstgravity.Ontheotherhand,tracheophytesaretallerand biggerbecausetheyhavetissuesystemthatintricate,thusenabletheseplants Debbra MarcelJP/8544/13 JIB 115 Plant Diversity: Assignment 1 distributenutrientstothewholeplantbodyandwillnoteasilybreakifhitbystrong wind. Thedominantlifeformofbryophytesisgametophytegenerationwhereasthe dominantlifeformofallthevascularplantsissporophytes.Inbryophytes,the dependantsporophytethatconsistsoffoot,setaandsporangiumisnourishedbythe gametophyte as it grows out the archegonium (female reproductive structure).On the otherhand,sporophyteisthedominantgenerationinthelifecycleofallthevascular plants.Thegametophyteofmostferns,thoughsmall,arephotosyntheticandnot dependantonthesporophytefortheirnutrition(free-living).Meanwhile,the gametophyte of seed plants develops within a confine of spore and surrounded by the tissues of the sporophyte, which the gametophyte derives its nutrition from.Bryophytesandsomepteridophytesarebothspore-bearingplantswherethe sporesaresinglecellwithnofoodsupplyandnoprotectivecoating,thusgivingtheir nameaslowerplants.Themalegamete(haploidstructure)ofbothbryophytesand pteridophytes consist of sperm that require water to swim into the femalereproductive organtofertilizetheegg.Meanwhile,thepresenceofseedinsteadofsporesin gymnosperms and angiosperms is the added adaptation that facilitated reproduction on land,thusgivingtheirnameashigherplants.Themalegamete(alsohaploid)of higherplantsisinpollenformandcanbedispersedbywindorpollinationbyother organisms. In higher plants, the multicellular seeds are supplied with nutritions from the sporophyte.Anotherextrafeaturethatpossesedbyangiospermsisthepresenceof flower, the complex reproductive structure that bears seed within protective chambers called ovaries. Variousotherfeaturesthatcanbeseeninbryophytescomparetoother respectivegroupofplantsinregardstotheevolutionarychangesandadaptationof terrestrial environment.The trend toward smaller and shorter life span of gametophyte invascularplantsistheevidentaslandplantsbecomeincreasinglyadaptedtoland environment, thus making sporophyte as the dominant stage in their life cycle. Debbra MarcelJP/8544/13 JIB 115 Plant Diversity: Assignment 1 5.The basic structural differences between bryophytes and vascular plants. The most obvious structural difference between bryophytes and vascular plants isthatbryophytesdonothaveavasculartransportsystem.Theabsenceofvascular tissue limits bryophytes to moist habitat and small sizes.Just like the thallus structure inmulticellularalgae,bryophyteshaveorgansthatappearsimilartotheroots,stems andleaves.However,thesestructuresarenotthetrueorgansandtherefore bryophytes unable to reach water under the soil instead absorb water directly from the environment (e.g rain, dew and fog), then the water that absorbed will move from cell tocellviaosmosis.Theroot-likestructureofbryophytescalledrhizoid,onlyactas anchorfortheprotonema(stem-likestructure)oftheplantsanddonotappeartobe involvedinabsorbingeitherwaterormineralsfromsoilbecausethisstructureisnot actually tissue/conductive tube but rather single or filamentous of cells. Instead, each partoftheseplantsobtainwaterdirectlyfromthemoistenvironment,thusmaking bryophytes live only in watery environment. In contrast with bryophytes, vascular plants have special transport tissuecalled xylem(waterandmineralsconductivetissue)andphloem(food/nutrientconductive tissue) that play the main role for the nutrients distribution in the vascular system.The specialnon-livingstructurecalledtracheidwhichcanonlybefoundinmostvascular plants(thusgivingthenametracheophytes),istheconductingtubeandsupportive elementofxylemthatcomposedoflong,thincellswithtaperedendsandwalls hardened with lignin thus enable these plants to grow far from the ground. The roots on thevascularplants absorbwaterandnutrientsfromsoilandpassitalongthroughout thexylemoftheplants.Meanwhile,thephloemdistributessugars,aminoacids,and otherorganicproductstothewholeplantbodythatproducedbyphotosynthesisin chloroplast. Besidesgettingwaterandfoodsourcesfromwetenvironment,thesurvivalof bryophytes also depend on the presence of moisture for reproduction to occur because theflagellatedmotilespermmustswimfromtheantheridium(malereproductive structure) into the archegonium (female reproductive structure) to fertilize the egg.The zygote that formed will remain inside archegonium and develop into sporophyte, which Debbra MarcelJP/8544/13 JIB 115 Plant Diversity: Assignment 1 hasshorterlifespanandfullydependentonthegametophyte.Asprimitivevascular plants,bryophytesarehomosporous,meaningthatthegametophytegenerationof bryophytesdevelopsoutsideofthesporewall(exosporic)andnormallybisexual (produce both sperms and eggs) in a single plant.All bryophytes can only grow from spores,whichreleasedfromthesporangium(spore-producingstructure).Whenthe capsule breaks open, the spores that discharged will be dispersed by wind, lay on the ground and new generation of gametophyte will germinate and finally become a mass green, branched, one-cell thick filament called protonema. Vascularplantshowever,consistofplantsthatgrowfromspores(seedless vascularplants)andplantsthatgrowfromseed(seedbearingplants/higherplants).Most seedless vascular plants do share the similar features of sperms and spores like bryophytes,butalsohavevascularsystemlikeothervascularplants.Infernsfor example,eventhoughfertilizedbyflagellatedmotilesperms,thesporophytesofthis seedless vascular plant are the larger generation as in the familiar leafy ferns, whereas the bisexual gametophytes that developed from a single spore are tiny plants that grow onorbelowthesoilsurface.Someseedlessplantsandallvascularplantsare heterosporous,havingtwotypesofspores/seedthatgiverisetomaleandfemale gametophytes. The seed plants have gametophyte that develops endosporically (inside thewallofseed)andsuppliedwithnutrientsandthedistributionoftheirpollensare aided by pollination or dispersal of wind. The presence of leaves increase the surface of plants, thereby enable vascular plantscapturingmoresolarenergyforphotosynthesis.Thestomata,whichisthe microscopic pore surround the cell wall in the epidermis of leaves and stems, allow the exchange of gas in the vascular plants.However, the stomata absence or can only be seen in the sporophyte generation of bryophytes.Moreover, some vascular plants like ferns, conifers and flowering plants have cuticle on their leaves surface to reduce water loss, which allow them to survive in relatively dry environment. Debbra MarcelJP/8544/13 JIB 115 Plant Diversity: Assignment 1 References 1.Campbell, N.A., & Reece, J.B. 2008. Biology. 6th ed. San Francisco (CA): Benjamin Cummings. pp. 662-670 2.Bidlack, J. E., Jansky, S. H. copyright 2014. Sterns Introductory Plant Biology. 13th ed. U.S.A: McGraw-Hill Education, International Edition. p. 517 3.Mauseth, James D. copyright 1998. Botany: An Introduction to Plant Biology. 2/e, Multimedia enhanced ed. Jones and Bartlett Publishers, Inc. p. 794 4.Bessho, K., Iwasa, Y. 2009. Heteromorphic and isomosphic alternation of generations in microalgae as adaptations to seasonal environment. Evolutionary Ecology Research. vol. 11: pp. 691-711 5.Niklas, K. J. and Kutschera, U. 2010. Transley review: The evolution of the land plant life cycle. Journal compilation New Phytologist. vol. 185. pp. 27-41