gymnosperms: “naked seeds” cycadophyta ginkophyta coniferaphyta gnetophyta

Gymnosperms:“naked seeds”

• Cycadophyta• Ginkophyta• Coniferaphyta• Gnetophyta

Seed plant recap: derived traits

• Reduced—microscopic—gametophytes• Protected within sporophyte• Dependent on sporophyte for nutrients

• Heterospory • different male and female reproductive structures

• Ovules (develops into seed)• Pollen (containing sperm)

Protection of gametophyte from environment

Protects sperm and allows fertilization w/o water

Protects and enhances embryo survival

Gymnosperm Origins

• Fossil evidence for seedplants 360 m.y.a.• Among the Carboniferous forests of seedless vascular plants• Fossil evidence of extant Gymnosperms ~ 305 m.y.a.• Drying climate 299-251 m.y.a. created environment where seedplants

had an adaptive advantage proliferation of gymnosperms• Extant Angiosperms arose 200 m.y. after extant gymnosperms

Gymnosperm diversity

4 taxa• Cycadophyta• Ginkophyta• Gnetophyta• Coniferaphyta – primary model

Cycadophyta (cycads)• Very prolific in Carboniferous period

• Flagellated sperm w/ in pollen tube

• Palm like w/ stroboli (cones)

• 200+ species

• Highly threatened today

Ginkophyta (Ginkos)• Flagellated sperm w/ in pollen tube• Deciduous

• Looses leaves

• Separate male and female plants (dioecious)• Females produce a fleshy seed that is stinky and undesirable…vomit like

• 1 species (not found in wild)• Long lived (up to 2500 yrs)

Gnetophyta• Non-flagellated sperm• Usually dioecious• Similarities w/ angiosperms

• Has vessel members• Double fertilization

• ~70 species

Welwitschia

Distribution of Gnetophyta genera

gnetum

ephedra

welwitschia

Coniferaphyta (Conifers):pines, firs, cedars, junipers, spruces, etc.

Coniferous forest dominated regions of world

Conifers• ~600 species• Mostly Northern Hemisphere—high latitudes & high altitudes/elevations• Non-flagellated sperm• Mostly Evergreen • Needle like or scale like leaves

• Clusters of needles organized by fascicles• Cold Adapted• Many are mycorrhizal dependent• Commercially important

• Lumber/timber-- Softwood (no fibers and thin tracheid walls)• Paper/wood pulp• Pine tar• Resin• turpentine

Southern Hemisphere Conifers

Pine Needle

Pine Needle

Cones = stroboli

• Most plants are monecious• Separate male and female cones

Male Cones & Pollen Formation

Pine Seeds: mostly wingedsome wingless varieties (birds, pine nuts..yum)