Units 22 and 23

Life Llife Cylce of
Nonseed Plant Life Cycle
Flagellated sperm must swim
Seed Plant Life Cycle
Pollination

Highlights in the History of Seed Plants
• Late in the Devonian, some plants developed secondary growth : thickened woody stems of xylem

How Did Seed Plants Become Today’s Dominant Vegetation?
Surviving seed plants fell into two groups:
• Gymnosperms : pines and cycads
• Angiosperms : flowering plants

• Any vascular plant that reproduces by means of an exposed seed, or ovule
• “Naked Seed”

Gymnosperm

Gymnosperms
Four major phyla of living gymnosperms:
• ( a)Cycads : Cycadophyta
 Sago palm
• Cone-bearing
• palm like
• tropical
• dinosaur food ?

Gymnosperms
• b)Ginkgos : Ginkgophyta
• One living species, Ginkgo biloba
• Seed coat stinks
• Polluted areas
• 1945 atom bomb
The ginkgo is a living fossil, recognizably similar to fossils dating back 270 million years.

Gymnosperms
• ( c) Gnetophytes : Gnetophyta
• Shrubs , trees, or vines
• the group is a small one, consisting of three families, each with one genus, totaling 68 species
Ephedra
*ephedrine

Gymnosperms
• (D)Conifers Coniferophyta
• largest group of gymnosperms
• pines, hemlock, spruce, evergreen conifers
• leaves stay all season
 sap ----antifreeze
• first real development of wood
 dead transport tissue

Gymnosperms
• Softwood

Angiosperms
• Flowering plants are the dominant plant today

Angiosperms
• They are the largest group of plants with about 90% of all plant species.
.

A
• Angiosperm
 Protected Seeds

Angiosperms
• FLOWERS are the exclusive reproductive organ of angiosperms
• “The earth laughs in flowers
” Ralph Waldo Emerson

What Features Distinguish the Angiosperms?
Angiosperm : “enclosed seed”

Angiosperms
• Male reproductive structures
Stamen



Anther
Filament bear microsporangia - sperm ( pollen)
Female reproductive structures
Carpel
Stigma, style, and ovary bear megasporangia -egg
(one or more carpel make up a pistil)

Angiosperm
• Pollen •
B - Dandelion (Taraxacum sp.) Transmission electron microscopy
• F Pine (Pinus sylvestis): Light microscopy
• G Mixed pollen grains (bright field light microscopy, stained)

Anigosperms
• Flowers may have contributed to the enormous success of angiosperms.
• The flowers attract a pollinators which carry pollen to other individuals of the same species

Angiosperms
Attracted to sweet smells
Need landing platform
Need bigger landing platform
Like bright colors
Attracted to strong smells
Can hover; nocturnal
Can hover
Prefer red color

Angiosperms
• Double fertilization
Sperm A leads to the formation of a Seed
Sperm B leads to the formation of an endosperm
(a nutritive tissue within the seed that feeds the developing plant embryo)

Flowering plants are divided into two groups

• Cotyledon?
• Embryonic seed
• is the first leaf or set of leaves that sprout from a seed
• Store nutrients for the embryo

• A cotyledon – “ seed leaf”
• contain nutrients for growth during embryonic development
• upon germination, the cotyledon may become the embryonic first leaves of a seedling.

• Dry fruit vs. Fleshy fruit