Download Seedless Vascular Plants Figure 21.1 The Evolution of Plants (Part 2)

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Seedless Vascular Plants
The empty niche – vertical growth
xylem
•  Further adaptations to land
–  Vascular system allows plants to
get tall
–  Origin of leaves (megaphylls)
•  Lycophytes
•  Ferns
–  Life cycle
–  Homospory and heterospory
Carboniferous
•  Horsetails etc
•  Key innovation –
vascular tissue for
movement of
nutrients against
gravity
phloem
March 6, 2017
Vascular systems permitted evolution of new
specialized plant organs
Fossil vascular plant (420 million years ago)
Branching,
independent
sporophyte
Roots
Leaves
Figure 21.1 The Evolution of
Plants (Part 2)
Cooksonia, the first vascular plant
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Sori – grouped
sporangia on
sporophylls
Dominant sporophyte
grows out of
gametophyte
Ferns
Lycophytes
Horsetails
Early vascular plant forest, carboniferous
period (300 million years ago)
Lycophytes
Ferns etc
Seed Plants
microphylls
The Lycophytes: sporedispersed plants with
microphylls
Vascular
Plants
Here are two lycophytes you can find in Vermont
Lepidodendron - the
scale tree of the Carboniferous
coal swamp
Shining clubmoss
Ground cedar
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Lycophytes
Ferns etc
Seed Plants
The Ferns and friends:
spore-dispersed plants
with true leaves
(megaphylls)
The remains of the Carboniferous scale trees
form the great coal deposits of the world
Vascular
Plants
megaphylls
Figure 21.10 Evolution of
Leaves
Ferns the second-most diverse group of
vascular plants
ca. 12,500 species
Fig. 29-13-3
Key
Haploid (n)
Diploid (2n)
MEIOSIS
Spore
dispersal
Spore
(n)
Sporangium
Sporangium
Antheridium
Young
gametophyte
Mature
gametophyte
(n)
Archegonium
Mature
sporophyte
(2n)
Sperm
Egg
New
sporophyte
Zygote
(2n)
FERTILIZATION
Sorus
Gametophyte
Fiddlehead
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All land plants alternate generations, although
extensively modified
Bryophyte
Homospory and
Heterospory
Pteridophytes Gymnosperm Angiosperm
Horsetails
Scouring rush
ca. 5 mm
Fern gametophyte with new sporophyte
Field horsetail
Vascular Plants
The Geologic Timetable
Climate was warming
and drying … not a
great time to be a
spore-dispersed plant!
Seed Plants
<Permian
Ferns and
Friends
seeds
Clubmosses
and friends
megaphylls
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