16 - & & ¢ £& ¤ £ ¤ The Evolution of...

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Unformatted text preview: & ¡ & ¢ ¡ £ & ¤ £ ¤ The Evolution of Plants - They Made the Land Green, Part 2 1.Friday – Diffusion HW due 2.Monday – Exam regrading request due Bryophytes - non-vascular plants • Three phyla: liverworts, hornworts, mosses • Abundant in moist habitats • Persistent gametophytes, ephemeral dependent sporophytes • Zygotes divide to form diploid embryos (young sporophytes) • Mature sporophyte often develops three parts - capsule (sporangium producing haploid spores via meiosis), seta (stalk), and foot embedded in gametophyte for nutrition. Liverwort Hornwort Moss F Fig. 30.7 1. First radiation of land plants - protection! Flowering plants F Fig. 30.9 Charophytes “Bryophytes” “Pteridophytes” Flowering plants #1 #4 #3 #2 cuticle/stomates enclosed embryo Land Plants = Embryophytes Pteridophytes - seedless vascular plants • major pteridophyte innovation was vascular tissue • xylem (water and ion transport) and phloem (sugar transport) • more efficient intercellular transport • greater size due to the hardening agent lignin in xylem • large sporophytes with vascular tissue • small free-living gametophytes without vascular tissue lycophytes ferns horsetails F Fig. 30.7 & ¡ & ¢ ¡ £ & ¤ & ¤ 2. Vascular plants - one major innovation Flowering plants F Fig. 30.9 Charophytes “Bryophytes” “Pteridophytes” Flowering plants #1 #4 #3 #2 cuticle/stomates enclosed embryo Vascular plants vascular tissue Gymnosperms - vascular plants with naked seeds • Major innovations - seeds and pollen (with very reduced, microscopic gametophytes) • 4 major groups with a total of 800 tree and shrub species • Dominant tree species at high elevations and high latitudes, plus certain arid environments F Fig. 30.7 Gymnosperms show 2 major innovations • The evolution of seeds – Megaspore -> Female gametophyte (with eggs) retained on sporophyte (termed an ovule) – Eggs fertilized in situ – Embryo supplied with food – Seed (or fertilized ovule) - a three generation package deal – Can wait for favorable conditions! – Can be carried by wind or animals See F Fig. 30.20 Gymnosperms show 2 major innovations • The evolution of seeds • The evolution of pollen (reduced male gametophyte) – Pollen can be carried by wind (et al.) to female gametophyte – Now free from water for reproduction! – Seed plants are viewed as genuine land plants pine pollen pollen cones seed cones & ¡ & ¢ ¡ £ & ¤ ¥ ¤ 3. Seed plants - two major innovations Flowering plants F Fig. 30.9 Charophytes “Bryophytes” “Pteridophytes” #1 #4 #3 #2 cuticle/stomates enclosed embryo Flowering plants Seed plants vascular tissue seeds, pollen Angiosperms - vascular seed plants with flowers and fruits as reproductive structures • 4th radiation of land plants - the origin of flowers • >250,000 species (~ 90% of land plants)...
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This note was uploaded on 04/05/2012 for the course BSCI 207 taught by Professor Higgins during the Spring '08 term at Maryland.

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16 - & & ¢ £& ¤ £ ¤ The Evolution of...

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