October 18-ch21 - • Plants provide fuel Human necessities...

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October 18, 2007 Chapter 21 Plants Key features of plants Multicellularity Ability to photosynthesize (most) o Small number of parasitic plants that have lost the need to photosynthesize Alternation of Generations o Diploid sporophyte plant produces haploid spore through meiosis o Spore divide by mitosis and develop into haploid gametophyte plants o Haploid gametophyte plant produces haploid gemmates through mitosis o Gametes fuse to form diploid zygotes, which divide by mitosis and develop into diploid sporophytes Multicellular dependent embryos Zygotes develop into multicellular embryos Crucial Ecological role Photosynthetic plants are the primary producers o Produces food directly or indirectly for all non-photosynthetic organism Photosynthetic plants produce oxygen gas Plants help create and maintin soil o Dead plant material is decomposed by fungi and other decomposers o Decomposed plant tissue becomes part of the soil, making it more fertile o Roots help hold soil together to help stop erosion Plants provide shelter
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Unformatted text preview: • Plants provide fuel Human necessities and Luxuries • Plants provide medicine o Aspirin: Willow o Taxol: yew o Morphine: poppy • Plants provide pleasure o Flowers, gardens, and lawns o Coffee, chocolate, tea, wine, fruits The plant evolutionary tree • Major steps in the evolution trees o Vascular system o Seeds and spores o Flowering and fruits Evolutionary Origin of Plants • Green algae • DNA similarties • Some tyhpes of cholorphyll and accessory pigments • Food stores as starch • Cell walls made of cellulose Early ancestors • Most green algae in fresh water o Suggests that early plants evolved in freshwater habitats • Early evolutionary pressure to withstand the challenges to freshwater habitat Terrestrial Adaptations • Roots are rootlike structures o Anchor plants o Absorb water from soil • Waxy cuticle covers leaves and stems o Reduces evaporative water loss • Stomata o Allow gas exchange when open o Can close and open •...
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October 18-ch21 - • Plants provide fuel Human necessities...

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