Units 22 and 23 SEED PLANTS. Life Llife Cylce of Nonseed Plant Life Cycle Flagellated sperm must...
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Transcript of Units 22 and 23 SEED PLANTS. Life Llife Cylce of Nonseed Plant Life Cycle Flagellated sperm must...
Units 22 and 23
•SEED PLANTS
Life Llife Cylce of
Nonseed Plant Life CycleFlagellated sperm must swim
Seed Plant Life CyclePollination
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
Gymnosperms
• 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 structuresCarpelStigma, 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 smellsNeed landing platform
Attracted to strong smellsCan hover; nocturnal
Can hoverPrefer red color
Need bigger landing platformLike bright colors
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