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Unformatted text preview: within megagametophyte Living seed plants Gymnosperms: “Naked seeds” Produce seeds that are totally exposed and found, e.g., on the scales of pine cones ~850 species Angiosperms: “Hidden seeds” Closed carpels enclosing ovule(s) Flowers Endosperm (double fer�liza�on) > 250,000 species Ovule (gymnosperm) Living seed plants Phyla: Coniferophyta: Conifers Cycadophyta: Cycads Ginkgophyta: Ginkgo Gymnosperms Gnetophyta: Ephedra, Gnetum, Welwitschia Magnoliophyta: ﬂowering plants Angiosperms 3 Seed plant rela�onships Seed plant rela�onships Conﬂic�ng phylogene�c hypotheses Conﬂic�ng phylogene�c hypotheses Fossil, morphological, molecular evidence -‐ What’s up with the Gnetophytes? Seed plant rela�onships New evidence: a phylogenomic approach Gymnosperms Some ex�nct gymnosperms: Seed “ferns” – diverse “group” Cordaitales – primi�ve conifer-‐like Caytoniales – ovule enclosed by a cupule (partly fused leaf-‐like structures) Benne�tales – resembled modern cycads; strobili (cones) similar to magnolia ﬂower Close rela�ves of angiosperms? Bennettitales “flower”
Cibrián-‐Jaramillo et al. 2010. Genome Biol. Evol. 2:225-‐239 [Lee et al. 2011. PLoS Gene�cs 7(12):e1002411] 4 Living gymnosperms Coniferophyta Conifers (~50 genera, 550 species) Cycadophyta Cycads (10-‐12 genera, ~250 species) Conifers Ecologically important: Occupy large areas of Earth Dominant plants of boreal/high al�tude forests Have large economic importance: – Lumber/building materials, paper products, landscaping, Christmas trees, u�lity poles, furniture, ﬂooring Ginkgophyta Ginkgo (1 species!) Gnetophyta Ephedra, Gnetum, Welwitschia (3 genera, 70 species) Conifers Most species are trees; some shrubs, no herbs Most species have persistent foliage ⇒ “evergreens” Simple, needle/scale-‐like leaves Most have both male and female reproduc�ve parts on the same plant (pollen/seed cones) Produce seeds within cones Conifers: Pine family (Pinaceae) Most species-‐rich conifer family Most of Northern Hemisphere 11 genera, ca. 250 spp Includes pine, spruce, ﬁr, hemlock, larch (deciduous) Larch (Larix)
Pine (Pinus) Fir (Abies)
Spruce (Picea) 5 Other conifers: Cypress family (Cupressaceae) Conifers: Pine family (Pinaceae) Most widely distributed conifer family The leaves are arranged ei...
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