alternation of generations in bryohyta and pteridophyta

1. 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
Alternation of generations
in mosses and ferns

2. 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
1. Adaptation to living on land and
the first land plants

3. 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.
Advantages of being small

4. Devonian
plant
community
Devonian plant community found at Rhynie, in Scotland.
A reed-like marsh, 370-380 million years ago.
Simple dichotomous branching
MAIN FEATURES
!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
Sporangia
Asteroxylon

5. Lycopodium
Lycopodium, club mosses, share many features with
Asteroxylon, but they do have roots.
http://web.utk.edu/~flemin00/pteridology/pteridology.html

6. http://www.ansci.cornell.edu/cgi-bin/db2www/plant_indiv.d2w/PHOTO?keynum=36
Equisetum arvense
Horsetails: Equisetum
Vegetative and
reproductive axis bearing
sporangia
The ‘scouring rush’

7. History of plant groups
2. History of evolution of major plant types
Fig. 17.3A

8. Alternation of generations
Fig. 17.4
3. Alternation of generations

10. Fig. 17.5
4. Moss life cycle

12. Moss sporophyte
Top of capsule

13. Developing protonema

14. Moss antheridium and archegonium

15. Fig. 17.3A

16. Fern life cycle
Fig 17.6
5. Fern life cycle

18. Sporangia Polypodium spp
sori
sporangia
http://departments.bloomu.edu/biology/chamuris/concepts2/labimg.html
A sorus

19. a
g
n
i
f
i
e
d
Polypodium spp
Sporangia
Developing spores

20. Gametophyte
Polypodium spp
Gametophyte
Developing sporophyte

21. Arrangement of sporangia on two ferns
In lines on a broadleaved type At the end of the leaves
Adiantum
Asplenium

22. Cibotium menziesii in habitat in
Hawaii. Photo courtesy of Peter Richardson.
Cyathea australis with the uncurling croziers
visible. Photo courtesy of Scott Ridges
Tree ferns

23. 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).
Coal formation
Anaerobic conditions and periodic inundations of
the sea

24. Early Carboniferous
Britain
Ice cap
Equator
Appalachians

25. Late Carboniferous
Britain
Ice cap
Equator
Appalachians

26. 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/Lepidophylloides1.html

27. 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