Plant Diversity I: How Plants
Colonized Land
Four Key Traits Plants share
with ancestor
• The four key traits that plants share with
charophyceans (algae) are:
• Rose-shaped complexes for cellulose synthesis: rose shaped
arrays of proteins in the plasma membrane that synthesize the
cellulose microfibrils of the cell walls.
• Peroxisome enzymes: contain enzymes that help minimize the
loss of organic products as a result of photorespiration.
• Structure of flagellated sperm: in certain species of land plants,
the structure of the flagellated sperm resembles the one that is in
the charophyceans.
• Formation of a phragmoplast: certain steps in cell division occur
only in land plants and some charophyceans;
Adaptations Enabling the Move
to Land
• Species of charophyceans: green algae
• live in shallow water in ponds and lakes (close
to the edges) – thus more chance of dry times
• Charophyceans have adapted:
• a layer of sporopollenin around zygote (also
seen around plant spores)
Morphological and Biochemical
Evidence
• Key characteristics of land plants are also
found in protists (mainly algae)
• Plants are:
• Multicellular
• Eukaryotic
• Photosynthetic autotrophs
Plants have…..
• Cell wall made of cellulose
• Apical meristem
• Alternation of generations
• Walled spores made in sporangia
• Multi-cell gametangia
• Cuticle (in some)
• Secondary compounds (in some)
• Alkaloides, tannins, flavonoids: bad flavor or
smell
Bryophyte Phyla
• Liverworts
• Named for shape of plant and the suffix -wort,
meaning herb.
• Hornworts
• Named for shape of plant and the suffix -wort,
meaning herb.
• Mosses
• Most familiar bryophytes
Bryophyte Gametophytes
• Gametophytes are a more dominant generation
and are most visible, such as moss.
• The flagellated sperm needs a covering of water
in order to travel to the eggs
Bryophyte Sporophytes
• Green and photosynthetic when young
• Cannot live independently
• Always attached to parental gametophytes;
sugars, amino acids, minerals and water are
obtained from them
• Bryophytes have the smallest and simplest
sporophytes
• Larger and more complex sporophytes came
later down the line when vascular plants
evolved
Sporophytes
• Contains
• Sporangium: produce spores by mieosis
•
•
•
•
Can make up to 50 million spores in one capsule
Spores are haploid
Spores have little food stored
Spores can survive for a long time in bad conditions
Origins and Traits of Vascular
Plants
• 420 million years old
• Have branched sporophytes
• NOT dependent on gametophyte
• Multiple sporangia
• Made production of spores easier
• Increased survival
Vascular plants (1st ferns)
• Life Cycles with Dominnant Sporophytes
• Transport in Xylem and Phloem
• Tracheids: tube cells in xylem
• Evolution of Roots
• Evolution of Leaves:
• Microphyls: needles, 1 vein
• Macrophyls: all other leaves w/ many veins
• Sporophylls: leaves on which spores grow.
Significance of Seedless
Vascular Plants
• “Seedless vascular plants dominated the
earliest forest. Their growth may have
helped produce the major global cooling
that characterized the end of the
Carboniferous period. The decaying
remnants of the first forests eventually
became coal.” (p. 590)
Evolution of Plants
• Bryophytes
• Hornworts
• Liverworts
• Mosses
• Seedless vascular plants
• Ferns
• Vascular plants with seeds
• Flowering vascular plants with seeds
Works Cited
• Information from:
• AP Biology Book
• www.course-notes.org
• Images from:
• AP Biology Book
• www.google.com