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Plants without seeds
1859, Sir William Dawson discovered fossilized remains of what he named
It had branching stems that ended in spore cases; and
appeared to lack roots and leaves.
1915, Robert Kidston and William Lang discovered fossils similar to
are examples of ancient terrestrial plants that lack
seeds and other features of more modern plants.
Seedless plants, such as mosses and ferns, are still abundant today.
Fossilized remains of seedless plants are primarily found in coal deposits.
WHAT IS A PLANT?
See Fig 28.1, p. 590
are photosynthetic species including: glaucophytes
(p. 579- first eukaryotic
group after cyanobacteria, retain peptidoglycans in chloroplast), red algae
s, and land plants
. This designation often used to include:
which are groups of green algae retaining egg in the parent
” designation includes: land plants, streptophytes and other green
all having chlorophyll b.
CHARACTERISTICS OF ALL PLANTS
photosynthetic autotrophs, mainly terrestrial
(vascular tissues well-defined in
photosynthetic with chlorophyll
chloroplasts with thylakoid membranes
cell wall contain cellulose (20-26%)
food reserve is the polysaccharide starch, stored in plastids
microtubular spindle, cell plate cytokinesis, sperm structure, DNA
evolution of plants from green algae
Fig 28.2, p. 591
-possibly from stoneworts (charophyte genus
branching and apical growth
(Chara) like most plants
basal growth as in liverworts)
microtubular cell division
- ancestral green algae lived at
margins of ponds or marshes
. From these marginal
habitats, early plants made the move onto land.
with multicellular gametangia
- zygote and embryo development is protected by tissues of parent body
alternation of generations life cycle
: two multicellular plant generations;
**Compare dominance of generations of different plant groups
Review this type of life cycle on page 592
( and p. 222 from last semester)