Alternation of generations in mosses and ferns

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Alternation of generations in mosses and ferns
1. Adaptation to living on land and the first
land plants
2. History of evolution of major plant types
3. Alternation of generations
4. Moss life cycle
5. Fern life cycle
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1. Adaptation to living on land and the first
land plants
The land that land plants colonized was hostile
to life. Soil development was minimal.
Land plants grow in an environment that does not
support them. They require several adaptations to
be successful
mechanical strength for support, exposed light
catching surfaces, anchoring system, conducting
system for water, system for obtaining mineral
nutrients, a way to restrict water loss in
desiccating air, a means of reproducing and
dispersing on land
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Advantages of being small
An advantage of being small is that many of the
requirements for living on land are
minimized. Close to the soil surface the
environment can be almost aquatic even if it
does not rain continuously. Then the principal
adaptation required becomes the ability to
withstand the dry periods between the wet.
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Devonian plant community
Devonian plant community found at Rhynie, in
Scotland. A reed-like marsh, 370-380 million
years ago.
MAIN FEATURES
Simple dichotomous branching
Sporangia
!5 to 30 cm tall
No roots
Stomata with guard cells
Most had a central vascular strand
Cuticle
Asteroxylon had leaves without a vascular
connection
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Lycopodium
Lycopodium, club mosses, share many features with
Asteroxylon, but they do have roots.
http//web.utk.edu/flemin00/pteridology/pteridolo
gy.html
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Horsetails Equisetum
Equisetum arvense
The scouring rush
Vegetative and reproductive axis bearing sporangia
http//www.ansci.cornell.edu/cgi-bin/db2www/plant_
indiv.d2w/PHOTO?keynum36
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History of plant groups
2. History of evolution of major plant types
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Alternation of generations
3. Alternation of generations
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4. Moss life cycle
Fig. 17.5
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Moss sporophyte
Top of capsule
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Developing protonema
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Moss antheridium and archegonium
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Fern life cycle
5. Fern life cycle
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Sporangia
http//departments.bloomu.edu/biology/chamuris/con
cepts2/labimg.html
Polypodium spp
sori
sporangia
A sorus
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Magnified sporangia
Polypodium spp
Sporangia
Developing spores
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Gametophyte
Polypodium spp
Developing sporophyte
Gametophyte
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Arrangement of sporangia on two ferns
In lines on a broadleaved type
At the end of the leaves
Adiantum
Asplenium
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Tree ferns
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Coal formation
Jungle-like forests of the Carboniferous were
dominated by giant ancestors of club mosses,
horsetails, ferns, conifers, and cycads.
Most of the plant fossils found in the coals and
associated sedimentary rocks show no annual
growth rings, suggesting rapid growth rates and
lack of seasonal variation in the climate
(tropical).
Anaerobic conditions and periodic inundations of
the sea
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Early Carboniferous
Equator
Appalachians
Britain
Ice cap
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Late Carboniferous
Equator
Appalachians
Britain
Ice cap
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Fossil
Lepidophylloides Lepidophylloides is the name
assigned to the leaves of the Lepidodendron tree
.  Rock Type Gray shale Age Middle
Pennsylvanian Period, approx. 312 million years.
http//www.clearlight.com/mhieb/WVFossils/Lepidop
hylloides1.html
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Sections you need to have read
17.1 17.2 17.3 17.4 17.5 17.6 17.7
Courses that deal with this topic
Botany 113 Plant Identification and
Classification
Botany 350 Introduction to Plant Geography
Geology 203 Evolution of the Earth