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AEBI 210- Nov 9th.doc

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McGill University
Biology (Agric & Envir Sc)
AEBI 210
Jaswinder Singh

Organisms 1- AEBI-210 001 November 9th, 2012 Non-Vascular Bryophytes- Land Invasions Evolution from Algae: Algae requires moist conditions, so can not survive on land Plants had to adapt to be able to move to land Cooksonia, which is non-vascular, is the first known land plant Green algae was likely the ancestor to land plants -Both have the same photosynthetic pigments -Store energy in starch and have cellulose -Have alternation of generations Evolutionary Challenges: Obtaining sufficient water -Roots developed to anchor the plant and absorb water and minerals Preventing water loss -Cuticle -Multicellular gametangia to protect gametes -Resistant coat on spores Obtaining sufficient energy -Using sunlight for photosynthesis -Developing support cells to grow tall above other plants -Adapting to lower light levels Obtaining gases for photosynthesis without loosing water -Stomata take in gasses during the day, and close to maintain water during the night Multicellularity -Evolved in algae -Allows for better rooting, gamete protection and growth to obtain sunlight -Vascular tissue had to develop to transport water to all cells Life Cycle -Became water independent -Developed dryness-resistant gametophytes/spores or zygotes/seeds -Many plants became larger -The sporophyte (2n) stage became dominant over the gametophyte (n) stage Bryophytes (Liverworts and Mosses): Organisms 1- AEBI-210 001 Thalloid or leafy plants that grow close to the ground in mostly moist locations Have apical meristems, rhizoids, stomata and cuticle but no vascular tissue or lignin Reproduce by sporic meiosis, with sporophytes that develop from the gametophyte Gametophores are the leafy structures which produce archegonia and antheridia Gametophyte generation is dominant Archegonia produce eggs antheridia produce sperm -The sperm fertilizes the egg, producing a sporophyte that grows i
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