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)