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