Lecture_9_Plants

Lecture_9_Plants - 6/15/2011 Why plants are important...

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6/15/2011 1 Plants LS1: Summer Session A July 13, 2011 Why plants are important Ecological roles Agriculture Commercial value Aesthetic value Source of pharmaceuticals Ecological importance of plants Dominant primary producers in terrestrial food chains Basis of organic carbon Ecological importance Carbon sequestration Ecological importance Plants help build and maintain soil Prevent erosion Buffer local climates Commercial value Agriculture Lumber Fuel Aesthetics
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6/15/2011 2 Pharmaceutical value Taxol = Pacific Yew Aspirin = Willow Bark Plants are Related to Green Algae Plants and green algae share Cellulose walls Photosynthetic starch Chlorophylls a and b Plants evolved from charophyte green algae 425-490 mya Plants have a suite a traits that adapt them to life on land Embryophytes Two evolutionary changes occurred in early in the history of land plants: (1) gametes were produced in complex multicellular structures and (2) the embryo was retained on the parent and nourished. Based on this innovation, biologists call the land plants embryophytes . Streptophytes Some biologists include some closely related forms of green algae in the designation “plants” This clade is referred to as the streptophytes
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6/15/2011 3 Plant relatives Challenges to terrestrial life Desiccation Support Acquisition of water Transport of water Delivery of gametes Ultraviolet radiation Adaptations to terrestrial life Cuticle Stomata Gametangia Embryos Pigments Spore walls (sporopollenin) Mycorrhizae Alternation of generations in the plant life cycle Homospory vs. Heterospory Plant groups Non-vascular plants Liverworts Hornworts Mosses Seedless vascular plants Lycophytes Monilophytes Gymnosperms Angiosperms
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6/15/2011 4 Non-vascular plant characteristics Found in wet or moist habitats Lack a vascular system or lignin Flagellated sperm Gametetangia produce gametes in sheltered structures Antheridia (male) Archegonia (female) Dominant gametophyte No true roots, stems, or leaves Major lineages of non-vascular plants Liverworts Phylum Hepatophyta (liverworts) Perhaps first land plants Simple thallus (gametophyte) No true stomata Some have gemmae (cuplike asexual reproductive structure on thallus) Major lineages of non-vascular
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Lecture_9_Plants - 6/15/2011 Why plants are important...

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