The Plant Kingdom: Seedless Plants
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Transcript of The Plant Kingdom: Seedless Plants
The Plant Kingdom:The Plant Kingdom:Seedless PlantsSeedless Plants
Chapter 27Chapter 27
Learning Objective 1Learning Objective 1
• What are some environmental challenges What are some environmental challenges of living on land?of living on land?
• How do some plant adaptations meet How do some plant adaptations meet these challenges?these challenges?
Colonization of Land by PlantsColonization of Land by Plants
• Required anatomical, physiological, and Required anatomical, physiological, and reproductive adaptationsreproductive adaptations
• Waxy Waxy cuticlecuticle • protects against water lossprotects against water loss
• StomataStomata• for gas exchange needed for photosynthesisfor gas exchange needed for photosynthesis
Alternation of GenerationsAlternation of Generations 11
• 2 parts of plant life cycle2 parts of plant life cycle• haploid haploid gametophyte generationgametophyte generation • diploid diploid sporophyte generationsporophyte generation
• Gametophyte plantGametophyte plant• produces gametes by mitosisproduces gametes by mitosis• gametes fuse (fertilization) to form gametes fuse (fertilization) to form zygotezygote
(first stage of sporophyte generation)(first stage of sporophyte generation)
Basic Plant Life CycleBasic Plant Life Cycle
Fig. 27-2, p. 582
Gametophyte
Spore Sperm Egg
HAPLOID (n) GAMETOPHYTE GENERATION
Meiosis Fertilization
DIPLOID (2n) SPOROPHYTE GENERATION
Zygote
Embryo
Sporophyte
Fig. 27-2, p. 582
Stepped Art
Spore
DIPLOID (2n) SPOROPHYTE GENERATION
Sporophyte
Zygote
Embryo
Sperm Egg
FertilizationMeiosis
HAPLOID (n) GAMETOPHYTE GENERATION
Gametophyte
Alternation of GenerationsAlternation of Generations 22
• Zygote develops into multicellular Zygote develops into multicellular embryoembryo• protected and nourished by gametophyteprotected and nourished by gametophyte
• Mature Mature sporophyte plantsporophyte plant• develops from the embryodevelops from the embryo• produces sporogenous cells (spore mother produces sporogenous cells (spore mother
cells)cells)
Alternation of GenerationsAlternation of Generations 33
• Sporogenous cells undergo meiosis to Sporogenous cells undergo meiosis to form form sporesspores • first stage in gametophyte generationfirst stage in gametophyte generation
KEY CONCEPTSKEY CONCEPTS
• Plants undergo an alternation of Plants undergo an alternation of generations between multicellular generations between multicellular gametophyte and sporophyte generationsgametophyte and sporophyte generations
Gametangia 1Gametangia 1
• Most plants have multicellular Most plants have multicellular gametangiagametangia• with protective jacket of sterile cells with protective jacket of sterile cells
surrounding gametessurrounding gametes
Gametangia 2Gametangia 2
• AntheridiaAntheridia• gametangia that produce sperm cellsgametangia that produce sperm cells
• ArchegoniaArchegonia• gametangia that produce eggsgametangia that produce eggs
GametangiaGametangia
Fig. 27-3a, p. 583
Developing sperm cells
Antheridium
Sterile cells
Fig. 27-3b, p. 583
Egg
ArchegoniumSterile cells
Vascular Transport SystemVascular Transport System
• In ferns and other vascular plantsIn ferns and other vascular plants• xylemxylem conducts water and dissolved minerals conducts water and dissolved minerals• phloemphloem conducts dissolved sugar conducts dissolved sugar
KEY CONCEPTSKEY CONCEPTS
• Adaptations to life on land that have Adaptations to life on land that have evolved in plants include a waxy cuticle to evolved in plants include a waxy cuticle to prevent water loss; multicellular prevent water loss; multicellular gametangia; stomata; and for most plants, gametangia; stomata; and for most plants, vascular tissues containing ligninvascular tissues containing lignin
Learning Objective 2Learning Objective 2
• From which green algal group are plants From which green algal group are plants hypothesized to have descended?hypothesized to have descended?
• Describe supporting evidenceDescribe supporting evidence
CharophytesCharophytes
• Plants probably arose from Plants probably arose from charophytescharophytes• a group of green algae a group of green algae
• Based on molecular comparisons of DNA Based on molecular comparisons of DNA and RNA sequencesand RNA sequences• close match between charophytes and plantsclose match between charophytes and plants
Plant EvolutionPlant Evolution
Fig. 27-4, p. 584
VASCULAR SEEDLESS PLANTS
VASCULAR SEED PLANTS
NONVASCULAR BRYOPHYTES
Ho
rnw
ort
s
Liv
erw
ort
s
Mo
sses
Clu
b m
oss
es
Fer
ns
Gym
no
sper
ms
An
gio
sper
ms
Evolution of seeds
Evolution of dominant sporophyte, vascular tissue
Evolution of cuticle, multicellular gametangia, multicellular embryos
Green algal
ancestor
KEY CONCEPTSKEY CONCEPTS
• Biologists infer that plants evolved from Biologists infer that plants evolved from aquatic green algal ancestors known as a aquatic green algal ancestors known as a charophytescharophytes
Insert “Evolutionary tree Insert “Evolutionary tree for plants”for plants”
plant_tree_v2.swfplant_tree_v2.swf
Explore plant evolution by Explore plant evolution by clicking on the figure in clicking on the figure in
ThomsonNOW. ThomsonNOW.
Learning Objective 3Learning Objective 3
• What features distinguish bryophytes from What features distinguish bryophytes from other plants?other plants?
BryophytesBryophytes
• Nonvascular (lack xylem and phloem)Nonvascular (lack xylem and phloem)• unlike other land plantsunlike other land plants
• Dominant gametophyte generationDominant gametophyte generation• unlike other plantsunlike other plants
• Sporophytes remain permanently attachedSporophytes remain permanently attached• nutritionally dependent on gametophytesnutritionally dependent on gametophytes
Learning Objective 4Learning Objective 4
• What are the three phyla of bryophytes?What are the three phyla of bryophytes?
Mosses (Phylum Bryophyta)Mosses (Phylum Bryophyta)
• Gametophytes are green plants that grow Gametophytes are green plants that grow from a filamentous from a filamentous protonema protonema
Liverworts (Phylum Hepatophyta)Liverworts (Phylum Hepatophyta)
• Many gametophytes are flattened, lobelike Many gametophytes are flattened, lobelike thallithalli (others are leafy) (others are leafy)
HornwortsHornworts (Phylum Anthocerophyta)(Phylum Anthocerophyta)
• Have thalloid gametophytesHave thalloid gametophytes
Fig. 27-5, p. 585
Fig. 27-5 (1), p. 585
No
nv
asc
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r b
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ph
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Va
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see
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Va
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Green algal
ancestor
KEY CONCEPTSKEY CONCEPTS
• Mosses and other bryophytes lack Mosses and other bryophytes lack vascular tissues and do not form true vascular tissues and do not form true roots, stems, or leavesroots, stems, or leaves
Learning Objective 5Learning Objective 5
• Describe the life cycle of mossesDescribe the life cycle of mosses
• Compare their gametophyte and Compare their gametophyte and sporophyte generationssporophyte generations
Mosses 1Mosses 1
• Green moss gametophyteGreen moss gametophyte• bears archegonia / antheridia at top of plant bears archegonia / antheridia at top of plant
• FertilizationFertilization• sperm cell fuses with egg cell in archegonium sperm cell fuses with egg cell in archegonium
(zygote)(zygote)
Mosses 2Mosses 2
• ZygoteZygote• grows into embryogrows into embryo• develops into moss sporophyte attached to develops into moss sporophyte attached to
gametophytegametophyte
Mosses 3Mosses 3
• MeiosisMeiosis• occurs within capsule of sporophyteoccurs within capsule of sporophyte• produces spores produces spores
• When spore germinatesWhen spore germinates• grows into a grows into a protonemaprotonema• forms buds that develop into gametophytesforms buds that develop into gametophytes
Moss Life CycleMoss Life Cycle
Fig. 27-6, p. 586
Gametophyte plants Antheridia at the tip of the gametophyte shootBuds on
protonema 1 Antheridia with sperm cellsSpore
germinates
Spores released 6
ProtonemaSperm cell
2HAPLOID (n) GAMETOPHYTE GENERATION
Archegonium with egg
Meiosis Fertilization
DIPLOID (2n) SPOROPHYTE GENERATION
5
Calyptra Zygote
Sporogenous cells that undergo meiosis
Capsule
Sporophyte4 3
Embryo
Gametophyte plant
Moss Moss SporophytesSporophytes
Fig. 27-7, p. 587
Capsule
Seta
Foot
Liverwort Life CycleLiverwort Life Cycle
Fig. 27-8, p. 588
AntheridiophoreArchegoniophore
Male thallusGermination of spores
and development of young gametophyte
1
Female thallus 5
Gemmae cup
Antheridia with sperm cells
Spores released Male and female
gametophyte plants
Sperm cell
HAPLOID (n) GAMETOPHYTE GENERATION
Archegonia with eggs 2
MeiosisDIPLOID (2n)
SPOROPHYTE GENERATION
Fertilization
4
Foot
SetaZygote
Tissue derived from archegonium Capsule Embryo
Sporogenous cells that undergo meiosis 3
Sporophyte
Insert “Moss life cycle”Insert “Moss life cycle”
moss_life_cycle_v2.swfmoss_life_cycle_v2.swf
Insert “Marchantia, a Insert “Marchantia, a liverwort”liverwort”
liverwort.swfliverwort.swf
Watch the life cycles of the Watch the life cycles of the mosses and liverworts by mosses and liverworts by clicking on the figures in clicking on the figures in
ThomsonNOW. ThomsonNOW.
Learning Objective 6Learning Objective 6
• What features distinguish seedless What features distinguish seedless vascular plants from algae and vascular plants from algae and bryophytes?bryophytes?
Seedless Vascular PlantsSeedless Vascular Plants
• Have adaptations that algae and Have adaptations that algae and bryophytes lackbryophytes lack• vascular tissuesvascular tissues• dominant sporophyte generation dominant sporophyte generation
• Reproduction depends on waterReproduction depends on water• as transport medium for motile sperm cells as transport medium for motile sperm cells
(as in bryophytes)(as in bryophytes)
Learning Objective 7Learning Objective 7
• What are the two phyla of seedless What are the two phyla of seedless vascular plants?vascular plants?
Club MossesClub Mosses (Phylum Lycopodiophyta) (Phylum Lycopodiophyta)
• Sporophytes consist of roots, rhizomes, Sporophytes consist of roots, rhizomes, erect branches, and erect branches, and microphylls microphylls (leaves(leaves))
Fig. 27-10a, p. 590
Stem
Microphyll
Vascular tissue Enation
Vein
Smooth stem
Enation Vascular supply to enation
Microphyll (one vein)
Club Club MossesMosses
Fig. 27-11 (1), p. 591
No
nva
scu
lar
bry
op
hyt
es
Vas
cula
r se
edle
ss p
lan
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Vas
cula
r se
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Green algal
ancestor
Fig. 27-11 (a-b), p. 591
Strobilus
Leaves (microphylls)
Ferns (Phylum Pteridophyta) Ferns (Phylum Pteridophyta)
• Largest and most diverse group of Largest and most diverse group of seedless vascular plants seedless vascular plants
• Fern sporophyte consists of a rhizome that Fern sporophyte consists of a rhizome that bears fronds and true roots bears fronds and true roots
• Includes Includes whisk fernswhisk ferns and and horsetailshorsetails
FernsFerns
Fig. 27-12 (1), p. 592
No
nva
scu
lar
bry
op
hyt
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Vas
cula
r se
edle
ss p
lan
ts
Vas
cula
r se
ed p
lan
ts
Green algal
ancestor
Fig. 27-12a, p. 592
Fig. 27-12b, p. 592
Fig. 27-12c, p. 592
Fern Life CycleFern Life Cycle
Fig. 27-13, p. 593
Underside of enlarged mature gametophyte (prothallus)
Germination of spores and development of young gametophyte Egg
4 5 ArchegoniumSpores released Rhizoids
3Antheridium
Sporangium HAPLOID (n) GAMETOPHYTE GENERATION
Sperm cell
MeiosisCells within sporangia undergo meiosis
Fertilization
Sorus (cluster of sporangia)
DIPLOID (2n) SPOROPHYTE GENERATION
2 Zygote
6Frond 1
Leaf of young sporophyte
Leaf cross section Development of the sporophyte
Fiddlehead Haploid prothallus
Roots RhizomeRoot of young sporophyte
Underside of a frond
Fern (mature sporophyte)
Whisk FernsWhisk Ferns
• SSporophytes have porophytes have dichotomously dichotomously branchingbranching rhizomes and erect stems rhizomes and erect stems• lack true roots and leaves lack true roots and leaves
Fig. 27-14a, p. 594
No
nva
scu
lar
bry
op
hyt
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Vas
cula
r se
edle
ss p
lan
ts
Vas
cula
r se
ed p
lan
ts
Green algal
ancestor
Fig. 27-14b, p. 594
Sporangia
Aerial stem with scalelike outgrowths (no leaves)
HorsetailsHorsetails
• Sporophytes haveSporophytes have• hollow, jointed roots, rhizomes, aerial stemshollow, jointed roots, rhizomes, aerial stems• leaves reduced to leaves reduced to megaphyllsmegaphylls
Fig. 27-10b, p. 590
Thicker main stem
Dichotomous end branches
Equal branches
Vascular tissue Thinner
side branch
Dichotomously branching
stems
Overtopping (unequal
branching)
Planation (branching in same plane)
Webbing of side branch
system
Megaphyll (many veins)
HorsetailsHorsetails
Fig. 27-15a, p. 594
No
nva
scu
lar
bry
op
hyt
es
Vas
cula
r se
ed
less
pla
nts
Vas
cula
r se
ed
pla
nts
Green algal
ancestor
Fig. 27-15b, p. 594
Strobilus
Vegetative shoots
Reproductive shoots
Insert “Seedless vascular Insert “Seedless vascular plants”plants”
seedless_vascular.swfseedless_vascular.swf
KEY CONCEPTSKEY CONCEPTS
• In club mosses and ferns, lignin-hardened In club mosses and ferns, lignin-hardened vascular tissues that transport water and vascular tissues that transport water and dissolved substances throughout the plant dissolved substances throughout the plant body have evolvedbody have evolved
Learning Objective 8Learning Objective 8
• Describe the life cycle of fernsDescribe the life cycle of ferns
• Compare sporophyte and gametophyte Compare sporophyte and gametophyte generationsgenerations
Fern SporophytesFern Sporophytes
• Roots, rhizomes, leaves are Roots, rhizomes, leaves are megaphyllsmegaphylls
• Leaves (Leaves (frondsfronds) bear sporangia in clusters ) bear sporangia in clusters ((sorisori))
• Meiosis in sporangia produces haploid Meiosis in sporangia produces haploid spores spores
Fern GametophyteFern Gametophyte
• Fern GametophyteFern Gametophyte (prothallus) (prothallus)• develops from haploid sporedevelops from haploid spore• bears both archegonia and antheridiabears both archegonia and antheridia
Insert “Fern life cycle”Insert “Fern life cycle”
fern_life_cycle_v2.swffern_life_cycle_v2.swf
Watch the life cycle of the ferns Watch the life cycle of the ferns by clicking on the figure in by clicking on the figure in
ThomsonNOW. ThomsonNOW.
Learning Objective 9Learning Objective 9
• What is the difference between the What is the difference between the generalized life cycles of generalized life cycles of homosporoushomosporous and and heterosporousheterosporous plants? plants?
HomosporyHomospory
• Production of one kind of sporeProduction of one kind of spore• in bryophytes, most club mosses, most ferns in bryophytes, most club mosses, most ferns
including whisk ferns and horsetailsincluding whisk ferns and horsetails
• Spores give rise to gametophyte plantsSpores give rise to gametophyte plants• produce both egg cells and sperm cellsproduce both egg cells and sperm cells
HeterosporyHeterospory 11
• Production of two kinds of spores Production of two kinds of spores ((microsporesmicrospores and and megasporesmegaspores))• in some club mosses and fernsin some club mosses and ferns• in all seed plantsin all seed plants
Heterosporous Life CycleHeterosporous Life Cycle
Fig. 27-16, p. 595
Gametophyte
Megaspore Gametophyte Archegonium
Microspore Antheridium
HAPLOID (n) GAMETOPHYTE GENERATION
Sperm Egg
Meiosis FertilizationDIPLOID (2n)
SPOROPHYTE GENERATION
Microsporocyte Zygote
Megasporocyte Microsporangium
EmbryoMegasporangium Sporophyte
HeterosporyHeterospory 22
• MicrosporesMicrospores • give rise to male gametophytes that produce give rise to male gametophytes that produce
sperm cellssperm cells
• MegasporesMegaspores• give rise to female gametophytes that give rise to female gametophytes that
produce eggsproduce eggs
SelaginellaSelaginella Life Cycle Life Cycle
Fig. 27-17, p. 596
Male gametophyte develops inside microspore wall
Single antheridium in male gametophyte produces many sperm cells3
Microspores5 Sperm cell
Ruptured megaspore wall
Archegonium containing egg
4Female gametophyte develops and protrudes from megaspore wall
Longitudinal section through archegonium
MegasporesHAPLOID (n)
GAMETOPHYTE GENERATION
Egg
Meiosis FertilizationMicrosporangium with microsporocytes
DIPLOID (2n) SPOROPHYTE GENERATION
Megasporangium with megasporocyte Strobilus
Female gametophyte
First leaves1 Leaf
(microphyll) Stem
Stem6
ZygoteLongitudinal section through strobilus
Root
Root Young sporophyte (attached to female gametophyte)Mature
sporophyte
Evolution of HeterosporyEvolution of Heterospory
• Essential step in evolution of seedsEssential step in evolution of seeds
• RhyniaRhynia
• AglaophytonAglaophyton