Biology 1010 Chapter 20

Biology 1010Biology 1010Chapter 20Chapter 20

BryophytesBryophytes

BryophytesBryophytes

►What are they??What are they??

►Where are they found??Where are they found??

►What is their evolutionary & ecological What is their evolutionary & ecological importance??importance??

Points to PonderPoints to Ponder

►Differentiate the bryophyte phyla from Differentiate the bryophyte phyla from each other and other phylaeach other and other phyla

►Describe the bryophyte adaptations to Describe the bryophyte adaptations to terrestrial environments terrestrial environments

►Describe reproduction in bryophyte Describe reproduction in bryophyte phylaphyla

►Describe the ecological role of Describe the ecological role of bryophytesbryophytes

Kingdom PlantaeKingdom Plantae►Bryophytes: simplest plantsBryophytes: simplest plants

Include liverworts, hornworts, mossesInclude liverworts, hornworts, mosses Fossils from 400 myaFossils from 400 mya

►Molecular evidence suggests 700 myaMolecular evidence suggests 700 mya

►Economically important speciesEconomically important species Sphagnum moss from peatlandsSphagnum moss from peatlands

►Cool northern areas: Canada, n. US, IrelandCool northern areas: Canada, n. US, Ireland►Modifies soil to retain HModifies soil to retain H22O, adds organic materialO, adds organic material

►Fuel sourceFuel source►Acid pH or antibiotic compounds: aid wound healingAcid pH or antibiotic compounds: aid wound healing

Bryophyte OverviewBryophyte Overview►Life on land possible whenLife on land possible when

Oxygen level Oxygen level > 2 %> 2 %►Present oxygen level??Present oxygen level??

Water can be retainedWater can be retained►Bryophytes found in moist Bryophytes found in moist

environmentsenvironments Term refers to Term refers to nonvascular plantsnonvascular plants

►Formerly one phylumFormerly one phylum

►Now: three phylaNow: three phyla Each evolved independently Each evolved independently From the same green algal ancestorsFrom the same green algal ancestors

Phylum HepatophytaPhylum Hepatophyta

► LiverwortsLiverworts 6000 spp6000 spp

► 11stst land plant fossil land plant fossil 450 mya450 mya Probably liverwortProbably liverwort

► Advantages of land:Advantages of land: Intense sunlightIntense sunlight Rocks rich in Rocks rich in

mineralsminerals

Phylum AnthocerophtaPhylum Anthocerophta► 100 spp100 spp

HornwortsHornworts

► Possible path of Possible path of evolution:evolution: Stranding of green Stranding of green

algae with prior algae with prior adaptationsadaptations

Adaptations include:Adaptations include:vertical stemsvertical stemsunderground stems underground stems for Hfor H22O & nutrient O & nutrient uptakeuptake

Phylum BryophytaPhylum Bryophyta► 9,600 spp9,600 spp

MossesMosses

► Bryophytes limited to Bryophytes limited to moist environmentsmoist environments Sperm requires waterSperm requires water

► Just as amphibians Just as amphibians dodo

Some can live in dry Some can live in dry sitessites

►Do not fossilize wellDo not fossilize well►Molecular evidenceMolecular evidence

700 mya700 mya

Bryophyte characteristicsBryophyte characteristics

►Nonvascular: no xylem & phloemNonvascular: no xylem & phloem Restricts size, limits distribution on landRestricts size, limits distribution on land

►Gametophytes have structuresGametophytes have structures Resemble stems & leaves Resemble stems & leaves

►Without internal ‘veins’Without internal ‘veins’

Hydroids: conduct HHydroids: conduct H22OO

Leptoids: conduct foodLeptoids: conduct food Thallus: body of a bryophyteThallus: body of a bryophyte Rhizoid: anchors bryophyte to substrateRhizoid: anchors bryophyte to substrate

►Absorption occurs through contactAbsorption occurs through contact

Bryophytes similar to Bryophytes similar to Charophyceae & vascular plantsCharophyceae & vascular plants► Classification of algae Classification of algae

& plants unsettled& plants unsettled Should reveal Should reveal

phylogenyphylogeny► Similarities between Similarities between

charophyceae & plantscharophyceae & plants Cellulose in cell wallsCellulose in cell walls Mitotic spindles remain Mitotic spindles remain

during cytokinesisduring cytokinesis Pigments:Pigments:

►Phytochrome, ChlPhytochrome, Chlaa, , bb, , carotenoids, carotenoids,

Thylakoids stacked in Thylakoids stacked in granagrana

Bryophytes similarity to Bryophytes similarity to plantsplants

►Characteristics that enhance survival on Characteristics that enhance survival on landland Protect gametes and sporesProtect gametes and spores

►Sterile cells protect structures producing male Sterile cells protect structures producing male and female gametesand female gametes

►multicellular embryo protected within female multicellular embryo protected within female parent parent

►Multicellular, diploid sporophyte meiosis Multicellular, diploid sporophyte meiosis → spores→ spores►Sterile cells protect multicellular sporangiaSterile cells protect multicellular sporangia

►Natural selection guided bryophyte Natural selection guided bryophyte evolution from green algae differently evolution from green algae differently than plantsthan plants

Bryophyte Bryophyte Alternation of GenerationsAlternation of Generations

► Gametophyte dominantGametophyte dominant HaploidHaploid Gametangia: mitosis Gametangia: mitosis → →

gametesgametes► Antheridia: maleAntheridia: male► Archegonia: female, one Archegonia: female, one

eggegg► Sporophyte attached to Sporophyte attached to

gametophytegametophyte Depends on gametophyte Depends on gametophyte

for its nutritionfor its nutrition DiploidDiploid Meiosis Meiosis →→ haploid spores in haploid spores in

sporangiumsporangium► Spore germinates Spore germinates → protonema→ protonema

Bryophyte Asexual Bryophyte Asexual ReproductionReproduction

► All 3 phyla can All 3 phyla can reproduce by reproduce by fragmentationfragmentation

► Reproduce through Reproduce through specialized brood specialized brood bodiesbodies GemmaeGemmae bulbilsbulbils

Ecological roles of Ecological roles of BryophytesBryophytes

►Plant successionPlant succession Mosses colonize rock surfaces, crevicesMosses colonize rock surfaces, crevices

►→ → soilsoil Rhizoids secrete acid to dissolve rockRhizoids secrete acid to dissolve rock Bodies add organic matter, collect dustBodies add organic matter, collect dust

►Seeds germinate in these pocketsSeeds germinate in these pockets►Epiphytic mosses:Epiphytic mosses:

Grow in tropical and temperate rain Grow in tropical and temperate rain forest treesforest trees

► Important in tundra Important in tundra NOT “reindeer moss” = lichenNOT “reindeer moss” = lichen

Bryophytes tolerate droughtBryophytes tolerate drought

► Liverworts may roll Liverworts may roll into tubeinto tube Protects upper Protects upper

surfacesurface► Tortula Tortula sppspp

Moss can dehydrateMoss can dehydrate Produce mRNAProduce mRNA

►Codes for protein Codes for protein to repair damageto repair damage

Rehydration Rehydration → → resumption of resumption of photosynthesisphotosynthesis

P. HepatophytaP. Hepatophyta= liverworts= liverworts

► Earliest land plants?Earliest land plants? Closely related to green Closely related to green

algaealgae Lack DNA characteristic Lack DNA characteristic

of other bryophytes, of other bryophytes, plantsplants

►Horizontal, flatter than Horizontal, flatter than mossesmosses Leaves usually thin, flatLeaves usually thin, flat

► Categories:Categories: Thalloid or leafyThalloid or leafy

Liverwort life cycleLiverwort life cycle►Gametophyte dominantGametophyte dominant

MarchantiaMarchantia Lobed gametophyte largeLobed gametophyte large

►Rhizoids penetrate soilRhizoids penetrate soil►Antheridia & archegonia Antheridia & archegonia

elevatedelevated►Antheridiophore Antheridiophore

flattened, bears flattened, bears antheridia, catch rain antheridia, catch rain dropsdrops

►Archegoniophore Archegoniophore suspends archegonia suspends archegonia beneath topsbeneath tops

Sporophyte Sporophyte inconspicuousinconspicuous►Zygote in archegoniumZygote in archegonium►Forms sporesForms spores

P. AnthocerophytaP. Anthocerophyta= hornworts= hornworts

► Conspicuous horn-Conspicuous horn-shaped sporophytesshaped sporophytes Stomata with guard Stomata with guard

cells: new featurecells: new feature

►Gametophytes Gametophytes similar to liverwortssimilar to liverworts Rumpled, green Rumpled, green

sheetsheet N-fixing bacteria N-fixing bacteria

symbiontssymbionts

Hornwort life cycleHornwort life cycle

►Gametophyte form antheridiaGametophyte form antheridia Become visible when sterile cells dry & breakBecome visible when sterile cells dry & break

►Archegonia form from surface cellsArchegonia form from surface cells Thallus cells surround eggThallus cells surround egg Fertilization Fertilization → zygote with ‘horn’→ zygote with ‘horn’

►Sporophyte foot anchors it to gametophyteSporophyte foot anchors it to gametophyte Gametophyte provides water, minerals, some Gametophyte provides water, minerals, some

foodfood►Sporophyte grows from its base not its apex Sporophyte grows from its base not its apex

photosynthetic as in liverworts, NOT mossesphotosynthetic as in liverworts, NOT mosses►Produces spores from apex of sporangium to baseProduces spores from apex of sporangium to base

P. BryophytaP. Bryophyta= mosses= mosses

►bryophytes refers to ALL nonvascular bryophytes refers to ALL nonvascular plantsplants

►P. Bryophyta = scientific classificationP. Bryophyta = scientific classification Mosses usually with a leafy thallusMosses usually with a leafy thallus Vertical gametophyteVertical gametophyte Usually in moist, forested sites, wetlandsUsually in moist, forested sites, wetlands Sometimes in deserts, dry rock outcropsSometimes in deserts, dry rock outcrops Some aquaticSome aquatic

Class SpagnopsidaClass Spagnopsidaaka Sphagnidaeaka Sphagnidae

► 150 spp, peat mosses150 spp, peat mosses► Sheet like protonemaSheet like protonema

Dead cells with thick Dead cells with thick walls hold waterwalls hold water

spherical sporangia spherical sporangia attach to stalks of attach to stalks of gametophytesgametophytes

Class AndreaeopsidaClass Andreaeopsida= granite or rock mosses= granite or rock mosses

► 100 spp100 spp► Live at high altitudesLive at high altitudes► Cold, temperate Cold, temperate

sitessites► Live on rock, snow, Live on rock, snow,

iceice► Sporangia with four Sporangia with four

slits allow dispersal slits allow dispersal of sporesof spores

Class BryopsidaClass Bryopsidaaka Bryidaeaka Bryidae

► 9,000 spp9,000 spp► Common mossesCommon mosses►Growth patterns varyGrowth patterns vary

May grow in clumpsMay grow in clumps As pendulous epiphytesAs pendulous epiphytes May remain May remain

filamentousfilamentous May be seasonalMay be seasonal May grow on polluted May grow on polluted

soilsoil

Life cycle of Life cycle of PolytrichumPolytrichum► Typical moss life cycleTypical moss life cycle

Dominant gametophyteDominant gametophyte►Survives droughtSurvives drought►Originates from sporeOriginates from spore

Spore → protonemaSpore → protonema►Bud → gametophyte Bud → gametophyte

leafleaf → → Antheridia &/or Antheridia &/or

archegoniaarchegonia►Water → fertilizationWater → fertilization

Zygote develops in Zygote develops in archegonium archegonium

→ → sporophyte with setaesporophyte with setae► foot absorbs foodfoot absorbs food

QuestionsQuestions

►Thought and DiscussionThought and Discussion►22►44►Evolution ConnectionEvolution Connection