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rav65819_ch30_581-602 - 30 Overview of Green Plants...

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;;;;;;;; 30 Overview of Green Plants introduction
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chapter PLANT EVOLUTION IS THE STORY of adaptation to terrestrial life by green algal ancestors. All green algae and land plants share a common ancestor, composing a monophyletic group called the green plants. For about 500 million years, algae were confined to a watery domain, limited by the need for water, which was necessary for reproduction, structural support, prevention of water loss, and some protection from the sun’s ultraviolet irradiation. Numerous evolutionary solutions to terrestrial challenges have resulted in over 300,000 species of plants dominating all terrestrial communities today, from forests to alpine tundra and from agricultural fields to deserts. Most plants are photosynthetic, and we rely on plants for food, clothing, wood for shelter and fuel, chemicals, and many medicines. This chapter explores the evolutionary history and strategies of the green plants. concept outline 30.9 The Evolution of Seed Plants The seed protects the embryo A pollen grain is the male gametophyte 30.10 Gymnosperms: Plants with “Naked Seeds” Conifers are the largest gymnosperm phylum Pines are an exemplary conifer genus Cycads resemble palms, but are not flowering plants Gnetophytes have xylem vessels Only one species of the ginkgophytes remains extant 30.11 Angiosperms: The Flowering Plants Angiosperm origins are a mystery Flowers house the gametophyte generation of angiosperms Most species use flowers to attract pollinators and reproduce The angiosperm life cycle includes double fertilization 30.1 Defining Plants
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Land plants evolved from freshwater algae Land plants have adapted to terrestrial life 30.2 Plant Life Cycles The haplodiplontic cycle produces alternation of generations The relative sizes of haploid and diploid generations vary 30.3 Chlorophytes: Aquatic Green Algae Chlorophytes can be unicellular Colonial chlorophytes have some cell specialization Multicellular chlorophytes can have haplodiplontic life cycles 30.4 Charophytes: Green Algae Related to Land Plants 30.5 Bryophytes: Nontracheophyte Green Plants Bryophytes are unspecialized but successful in many environments Liverworts are an ancient phylum Hornworts developed stomata Mosses have rhizoids and water-conducting tissue 30.6 Features of Tracheophyte Plants Vascular tissue allows distribution of nutrients Tracheophytes include seven extant phyla grouped in three clades Seeds are another innovation in some phyla 30.7 Lycophytes: The Club Mosses 30.8 Pterophytes: Ferns and Their Relatives Whisk ferns lost their roots and leaves secondarily Horsetails have jointed stems with brushlike leaves Ferns have fronds that bear sori 581 rav65819_ch30_581-602.indd 581 rav65819_ch30_581-602.indd 581 12/7/06 2:00:25 PM 12/7/06 2:00:25 PM 30.1 Defining Plants As you saw in chapter 26, the phylogenetic revolution has completely altered our definition of a plant. We
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