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Plants
(Seedless)
Learning Objectives
• By the end of this unit, a student should be able to…
• Describe the characteristics and distinguish among the major groups of
seedless plants
• Diagram the “alternation of generations” life cycle
• Discuss challenges of adapting to life on land and which adaptations in
plants evolved in response.
• Describe the evidence suggesting the hypothesized relationship between
plants and the charophytes
• Summarize the features that distinguish bryophytes from other plants
• Name and describe the phyla of bryophytes
• Compare the gametophyte and sporophyte generations in bryophytes
• Discuss features that distinguish seedless vascular plants from algae and
bryophytes
• Distinguish between the lycophytes and the ferns
ARCHAEPLASTIDS
• Red algae
• Green algae
• Land plants
• Monophyletic based on
• molecular data
• presence of chloroplasts bound by outer and inner membranes
Green Algae
• Wide diversity in
size, structural
complexity, and
reproduction
Charophytes
• Plants probably arose from charophytes
• a group of green algae
• close match between charophytes and plant DNA and
RNA sequences
Charophytes
• Plants probably arose from charophytes
• a group of green algae
• close match between charophytes and plant DNA and
RNA sequences
Gametangia in Charophytes are
different than other plants.
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5
–
–
– Zoospores
ASEXUAL
REPRODUCTION (by
mitosis)
–
–
4 Four haploid
cells emerge, two
(+)
and two
(-).
1 Gametes are produced
by mitosis. +
–
– – SEXUAL
REPRODUCTION
+ HAPLOID (n)
GENERATION
–
+ –
DIPLOID (2n)
GENERATION 2 (+) and (-)
gametes fuse,
forming a diploid
zygote.
+ Meiosis Fertilization
3
Meiosis
occurs. Zygote (2n)
Chlamydomonas
• Chlamydomonas has
isogamous sexual
reproduction
Ulva
• Ulva has
anisogamous
sexual reproduction
Plant Life Cycle
“Alternation of Generations”
Plant Life Cycle
• Alternation of Generations
• Haploid gametophyte
• produces gametes by
mitosis
• gametes fuse
(fertilization) to form
diploid zygote
• Diploid sporophyte
• Zygote develops into
multicellular embryo/plant
• produces sporogenous
cells (mother cells)
“Land Plants”
What are environmental challenges of living on land?
How do plant adaptations meet these challenges?
Colonization of Land by Plants
• Adaptations
• Anatomical
• of or relating to bodily structure
• Physiological
• of or relating to the way in which a living organism or
bodily part functions
• Reproductive
• of or relating to the production of offspring by a sexual
or asexual process
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Colonization of Land by Plants
• Cuticle
• waxy layer
• protects against water
loss
• Stomata (stomates)
• for gas exchange
needed for
photosynthesis –Johnny Appleseed
“Type a quote here.”
VASCULAR
SEEDLESS PLANTS
VASCULAR
SEED PLANTS
NONVASCULAR BRYOPHYTES
Ho
rnw
ort
s
Liv
erw
ort
s
Mo
sses
Clu
b m
osses
Fern
s
Gym
no
sp
erm
s
An
gio
sp
erm
s
Evolution of
seeds
Evolution of dominant
sporophyte, vascular
tissue
Evolution of cuticle,
multicellular gametangia,
multicellular embryos Green algal
ancestor
Bryophytes
• Bryophyte characteristics
• Nonvascular
• lack conducting tissues
• xylem & phloem
• must remain relatively small
• Gametophyte generation is dominant
• unlike other plant groups
• sporophytes remain permanently
attached
• nutritionally dependent on
gametophytes
Hornworts
• Phylum Anthocerophyta
• ~100-150 species
• Thalloid gametophytes
• Horn-like sporophytes
Liverworts
• Phylum Marchantiophyta
• ~ 9000 species
• Some have flattened, lobed thalloid gametophytes
• resemble lobes of the liver
• most are “Leafy” gametophytes
Fig. 27-4, p. 584
VASCULAR SEED PLANTS
Evolution of seeds
Evolution of dominant sporophyte, vascular
tissue
Evolution of cuticle, multicellular gametangia,
multicellular embryos
Green algal ancestor
Liverworts
• Pores, not stoma for gas
exchange
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Fig. 27-4, p. 584
VASCULAR SEED PLANTS
Evolution of seeds
Evolution of dominant sporophyte, vascular
tissue
Evolution of cuticle, multicellular gametangia,
multicellular embryos
Green algal ancestor
Liverworts
• Asexual Reproduction
• Gemmae cups
Fig. 27-4, p. 584
VASCULAR SEED PLANTS
Evolution of seeds
Evolution of dominant sporophyte, vascular
tissue
Evolution of cuticle, multicellular gametangia,
multicellular embryos
Green algal ancestor
Liverworts
• Sexual Reproduction
• Antheridophore
• hold antheridia
• Archegoniophore
• hold archegonia
Liverworts
• Liverwort sperm cell
Pellia epiphylla
Video of liverwort sperm
Fig. 27-4, p. 584
VASCULAR SEED PLANTS
Evolution of seeds
Evolution of dominant sporophyte, vascular
tissue
Evolution of cuticle, multicellular gametangia,
multicellular embryos
Green algal ancestor
Mosses
• Phylum Bryophyta
• ~12,000 spp.
• Gametophytes (n)
• grow from protonema
• branching, filamentous stage
Fig. 27-4, p. 584
VASCULAR SEED PLANTS
Evolution of seeds
Evolution of dominant sporophyte, vascular
tissue
Evolution of cuticle, multicellular gametangia,
multicellular embryos
Green algal ancestor
Mosses
• Phylum Bryophyta
• ~12,000 spp.
• Gametophytes (n)
• grow from protonema
• branching, filamentous stage
Mosses
Fig. 27-4, p. 584
VASCULAR SEED PLANTS
Evolution of seeds
Evolution of dominant sporophyte, vascular
tissue
Evolution of cuticle, multicellular gametangia,
multicellular embryos
Green algal ancestor
• Sporophytes (2n)
• produce capsules
• contain spores
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Seedless
Vascular
Plants
Ferns
Fern Allies
Lycopods
–Johnny Appleseed
“Type a quote here.”
VASCULAR
SEEDLESS PLANTS
VASCULAR
SEED PLANTS
NONVASCULAR BRYOPHYTES
Ho
rnw
ort
s
Liv
erw
ort
s
Mo
sses
Clu
b m
osses
Fern
s
Gym
no
sp
erm
s
An
gio
sp
erm
s
Evolution of
seeds
Evolution of dominant
sporophyte, vascular
tissue
Evolution of cuticle,
multicellular gametangia,
multicellular embryos Green algal
ancestor
Seedless Vascular Plants
• What features distinguish
seedless vascular plants from
algae and bryophytes?
Seedless Vascular Plants
• What features distinguish
seedless vascular plants from
algae and bryophytes?
xylem and phloem in a
lycopod stem cross section
Vascular tissue and much
larger, dominant sporophyte
Lepidodendron from the
carboniferous period
Seedless Vascular Plants
• In vascular plants
• xylem conducts water and
dissolved minerals
• phloem conducts dissolved sugar
xylem
xylem and phloem in a
lycopod stem cross section Lepidodendron from the
carboniferous period
phloem
Seedless Vascular Plants
• Sporophyte is larger
• increases spore dispersal
• gametophytes still need water for
reproduction
• sperm swim to eggs
xylem
“fern sperm”
fern gametophyte
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–Johnny Appleseed
“Type a quote here.”
Fig. 27-4, p. 584
VASCULAR SEEDLESS
PLANTS
VASCULAR SEED
PLANTS
NONVASCULAR BRYOPHYTES H
orn
wo
rts
Liv
erw
ort
s
Mo
sses
Clu
b m
osses
Fern
s
Gym
no
sp
erm
s
An
gio
sp
erm
s
Evolution of
seeds
Evolution of cuticle, multicellular
gametangia, multicellular embryos Green algal
ancestor
“Club Mosses” are the Lycopods
They are not mosses
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
osses
Fern
s
An
gio
sp
erm
s
Evolution of
seeds
Evolution of cuticle, multicellular
gametangia, multicellular embryos Green algal
ancestor
Lycopods
• Lycopods have microphylls
• a different way of forming vascular tissue in the leaves
Stem Microphyll
Vascula
r tissue Enation
Vein
Smooth
stem Enation Vascular
supply to
enation
Microphyll
(one vein)
Lycopods
• 3 extant (not extinct) lineages
• there used to be more
Isoetes
Selaginella
Lycopodium
Lycopods
Lycopodium
• Lycopodium (ground pine)
• flammable spores!
Lycopods
Lycopodium
• Lycopodium (ground pine)
• flammable spores!
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Lycopods
Isoetes
• Isoetes (quillworts)
• mostly aquatic
• no stomata
• obtain CO2 From roots
Lycopods
Selaginella
• Selaginella (spike moss)
• Kinda cute
• Evolved heterospory
microspores megaspores
HOMOSPORY
HETEROSPORY
microspores
megaspores
give rise to female gametophytes
that produce eggs
give rise to male gametophytes
that produce sperm
Lycopods
• Selaginella (spike moss)
• Gametophytes highly
reduced
• Much like a seed
• (convergent evolution)
Selaginella Life Cycle
Remember that
the life cycle is
the same in all
plants!
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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
osses
Fern
s
Gym
no
sp
erm
s
An
gio
sp
erm
s
Evolution of
seeds
“Club Mosses” = Lycopods
Evolution of cuticle, multicellular
gametangia, multicellular embryos Green algal
ancestor
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
osses
Fern
s
Gym
no
sp
erm
s
An
gio
sp
erm
s
Evolution of
seeds
Evolution of cuticle, multicellular
gametangia, multicellular embryos Green algal
ancestor
FERNS (PHYLUM PTERIDOPHYTA)
Psilotum
Equisetum
“Ferns”
Ferns (Phylum? Division?)
Psilotum
Ferns
• Psilotum (Whisk Fern)
• Leafless, dichotomous branches
• “odd” sporangia
Psilotum
Ferns
• Psilotum (Whisk Fern)
• small non-photosynthetic
gametophytes
• but with vascular tissue!
• nourished by mychorrizae Thinner
side
branch
Dichotomously
branching stems
Overtopping
(unequal
branching)
Planation
(branching in
same plane)
Webbing of side
branch system
Megaphyll (many
veins)
Equal branches
Vascular tissue
Ferns
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Thinner
side
branch
Dichotomously
branching stems
Overtopping
(unequal
branching)
Planation
(branching in
same plane)
Webbing of side
branch system
Megaphyll (many
veins)
Equal branches
Vascular tissue
Ferns
• Sporophytes have megaphylls (leaves)
Megaphyll vs. Microphyll
• Sporophytes consist of roots, rhizomes, erect
branches, and microphylls (leaves)
Psilotum
Equisetum “Ferns”
FERNS (PHYLUM PTERIDOPHYTA)
Equisetum
FERNS (PHYLUM PTERIDOPHYTA)
Ferns
• Equisetum
• hollow, jointed roots, rhizomes, aerial
stems
• strobili
Strobilus
Vegetative
shoots
Reproductive
shoots
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Ferns
• Equisetum
• Large, tree-like species now extinct
• once prominent
• The “Coal Age” (Carboniferous)
Psilotum
Equisetum “Ferns”
FERNS
FERNS • Largest and most diverse group of seedless vascular plants
• Sporophyte leaves are called fronds
• often unfurl during development
FERNS
• Sporophyte has a rhizome
• Horizontal, underground stem
• bears fronds
• has true roots
FERNS
Rhizome
• Fronds contain sporangia
• Clustered in a Sorus
• produces many spores!
FERNS
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• Fronds contain sporangia
• Clustered in a Sorus
FERN GAMETOPHYTE • Fern Gametophyte is called a prothallus
• develops from haploid spore
• bears both archegonia and antheridia
FERN LIFE CYCLE