3/5/17 1 Seedless Vascular Plants • Further adaptations to land – Vascular system allows plants to get tall – Origin of leaves (megaphylls) • Lycophytes • Ferns – Life cycle – Homospory and heterospory • Horsetails etc March 6, 2017 Carboniferous The empty niche – vertical growth • Key innovation – vascular tissue for movement of nutrients against gravity xylem phloem Vascular systems permitted evolution of new specialized plant organs Roots Leaves Fossil vascular plant (420 million years ago) Branching, independent sporophyte Cooksonia, the first vascular plant Figure 21.1 The Evolution of Plants (Part 2)
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Seedless Vascular Plants The empty niche – vertical growth · Seedless Vascular Plants • Further adaptations to land – Vascular system allows plants to get tall – Origin of
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Seedless Vascular Plants
• Further adaptations to land – Vascular system allows plants to
get tall – Origin of leaves (megaphylls)
• Lycophytes • Ferns
– Life cycle – Homospory and heterospory
• Horsetails etc
March 6, 2017
Carboniferous
The empty niche – vertical growth
• Key innovation – vascular tissue for movement of nutrients against gravity
xylem
phloem
Vascular systems permitted evolution of new specialized plant organs
Roots
Leaves
Fossil vascular plant (420 million years ago)
Branching, independent sporophyte
Cooksonia, the first vascular plant
Figure 21.1 The Evolution of Plants (Part 2)
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Lycophytes
Ferns
Horsetails
Sori – grouped sporangia on sporophylls
Dominant sporophyte grows out of gametophyte
Early vascular plant forest, carboniferous period (300 million years ago)
Vascular Plants
The Lycophytes: spore-dispersed plants with microphylls
Lycophytes Ferns etc Seed Plants
microphylls
Here are two lycophytes you can find in Vermont
Ground cedar Shining clubmoss
Lepidodendron - the scale tree of the Carboniferous coal swamp
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The remains of the Carboniferous scale trees form the great coal deposits of the world
Vascular Plants
The Ferns and friends: spore-dispersed plants with true leaves (megaphylls)
megaphylls
Lycophytes Ferns etc Seed Plants
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
Sporangium
Sporangium Mature sporophyte (2n)
Sorus
Fiddlehead
Spore (n)
Young gametophyte
Mature gametophyte (n) Archegonium
Egg
Antheridium
Sperm
FERTILIZATION New sporophyte
Gametophyte
Zygote (2n)
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Bryophyte Pteridophytes Gymnosperm Angiosperm
All land plants alternate generations, although extensively modified Homospory and
Heterospory
Fern gametophyte with new sporophyte
ca. 5 mm
Horsetails
Scouring rush
Field horsetail
The Geologic Timetable
<Permian Climate was warming and drying … not a great time to be a spore-dispersed plant!