GYMNOSPERMS Naked Seeds General Characteristics u Vascular u

GYMNOSPERMS “Naked Seeds”

General Characteristics u Vascular u Alternation of generations – Dominant sporophyte – Reduced, dependent gametophyte u Produce uncovered seeds

4 Phyla of Gymnosperms u Cycads u Gingko u Conifers u Gnetophytes

Cycads u Most diverse during age of dinosaurs u Only 100 living species u Palmlike appearance u Pollen-bearing and seed-bearing cones on different plants Strobilus of a “female” cycad

Ginkgos u Diverse during age of dinosaurs u One surviving species, Ginkgo biloba u Deciduous trees are male or female u Seeds are completely exposed

Gnetophytes u Share some traits with angiosperms – Xylem – Cone clusters resemble flower clusters – Parts of life cycle more like angiosperms

Conifers u Widest known, largest number of living species u Woody trees or shrubs u Most are evergreen u Bear seeds on exposed cone scales u Most produce woody cones

Pine Cones u Woody scales of a “pine cone” are the parts where megaspores formed and developed into female gametophytes u Male cones, where microspores and pollen are produced, are not woody

Life cycle of typical conifer

Animation: Pine Life Cycle CLICK TO PLAY

Conifer Distribution u Reproduce more slowly than angiosperms; at competitive disadvantage in many habitats u Still dominate in far north, at higher elevations, and in certain parts of southern hemisphere