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,
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
Then the principal adaptation required becomes
the ability to withstand the dry periods between
Advantages of being small
Devonian plant community found at Rhynie, in Scotland.
A reed-like marsh, 370-380 million years ago.
Simple dichotomous branching
!5 to 30 cm tall
Stomata with guard cells
Most had a central vascular strand
Asteroxylon had leaves –
without a vascular connection
22. Cibotium menziesii in habitat in
Hawaii. Photo courtesy of Peter Richardson.
Cyathea australis with the uncurling croziers
visible. Photo courtesy of Scott Ridges
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).
Anaerobic conditions and periodic inundations of
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