L4 Gymnosperms

L4 Gymnosperms - 1. 2. 3. 4. TheChallenge:DealingwithGravity

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Review of Lecture 3 1. The Challenge: Dealing with Gravity 2. The Seedless Vascular Plants  3. The Innovation: Introducing  LIGNINS 4. The Benefits: expanding your territory a) Harvesting light energy b) Staying wet (conducting tissues) 5. Fossil records (the missing pieces) 6. Alternation of generations: Achieving independence
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The Seedless Vascular Plants: Chapter  21 1. Dealing with gravity a) Harvesting light energy 2. Staying wet when things get dry a) Conducting tissues (vasculature)
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Innovation… Strength through chemistry……. LIGNINS
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The Seedless Vascular Plants (SVPs) LIGNINS  strengthen cell walls by replacing  water and coating or encrusting the  cellulose  (the principle building block of  plant cells walls: chains of glucose  molecules)  Bryophytes  do not  have lignins
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Life Cycles   Alternation of generations (all plants) Seedless Vascular Plants 2n 1n 1. Sporophyte is  dominant (if you encounter a SVP, you are most likely looking at the sporophyte) 2. Gam etophyte is significantly reduced in  physical size 3. The sporophyte and gam etophyte are  independent at m aturity (unlike  Bryophytes and seed plants)  Seedless Vascular Plants (SVPs)
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Members of Psilotophyta, Lycophyta, and  Sphenophyta  have  microphylls  (leaves that have a  single vascular trace or leaf vein (no leaf gap) Chap. 21, Pg.451.
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Chap. 21, pg. 455 Phylum Pterophyta: earliest group of plants to  have  megaphylls
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The challenges 1. Harvesting light energy 2. Staying wet when things get dry 3. Dealing with gravity 4. Divide or be conquered  5. Leveraging resources
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Harvesting light energy The trends… vasculature Single cells with light  harvesting machinery Light harvesting  multicellular organs Stems with enations or  microphylls
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Staying wet The trends… vasculature Cuticles and  stomata Conducting  systems Conducting systems
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The trends… buoyancy…. remaining small
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This note was uploaded on 12/23/2010 for the course BIOL 120 taught by Professor Chuong during the Spring '09 term at Waterloo.

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L4 Gymnosperms - 1. 2. 3. 4. TheChallenge:DealingwithGravity

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