Biology lecture 3/16/15Intro to Plantae1. Origins of plants2. Plant adaptations to terrestrial environments3. Plant life cycle: alternation of generationsPlants: Some unifying features- Eukaryotic- Photoautotrophic (oxygenic)- All multicellular- Primarily terrestrialOrigins of plants- Terrestrial incursion approximately 475 mya- Indicated only by sporesPlants adaptation to a terrestrial environment:1. Apical meristematic growth2. Spores/pollen walls with sporopollenin3. Multicellular gametangia:Multicellular gametangia: antheridia and archegoniaAntheridia: sperm productionArchegonia: egg production and zygote retentionMeristems: regions of rapidly dividing/undifferentiated cellsApical meristems: permit directed upward-downward growthSporopollenin: very stable polymer of plant spores and pollenThe exact chemical composition is unknownPlant life cycleAll plants exhibit a “heteromorphic alternation of generations”2 distinct multicellular states of heteromorphic alternation of generations: Sporophyte (diploid) and Gametophyte (haploid)Sporophyte (diploid): produces haploid spores via meiosisGametophyte (haploid): produces gametesQuizlet link:
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