BIO 1150 1st Edition Lecture 19Chapter 27 Topic Discussed: How Plants Colonized the Land3 billion years, life only found in waterMoving to land required adaptations to prevent water lossLand plants evolved from green algae (charophytes)Karophytis-higher plants seen on earthCharophytes- closest relatives to embryophytes (today’s plants)Derived traits of land plants1. Alternation of generations and multicellular dependent embryos2. Walled spores (w/ sporopollenin) produced in sporangia3. Multicellular gametangia4. Apical meristems5. Otherso Cuticle- resist drying outo Symbiotic associations with fungi (mycorrhizae)o Secondary compounds, ex. lignin for cell wall reinforcement1. Alternation of generations- involves haploid and diploid multicellular stages- Gradual reduction of haploid stage (gametophyte) and loss of reliance on water is an evolutionary patterno Diploid- produces sporeso Haploid- produces gametes2. Sporangia produce haploid spores by meiosis- Multicellular gametangia produce haploid gametes by mitosis- Model systems- mouse/ fruitfly, archaegonia3. Embryophytes retain embryo- Plants can grow larger/ reproduce better4. Apical meristem– elongation (root, shoot)Non-vascular plants (lower/older plants)1. Phyla: Hepatophyta (liverworts)2. Bryophyta (mosses)3. Anthocerophyta (hornworts)- Life cycle dominated by large gametophyte- Sporophyte is small and dependent on gametophyteHepatophyta(liverworts)- Moist enviroments- Have thallusAntherocerophyta- Sporophytes- “horns” and spores are produced on topBryophyta(moss)- Gametophyte-bottom leafy stuff- Sporophytes- topo Stage of drying- spores will pop off- Mosses retain nitrogen in soil- Stores carbono Peat (sphagnum moss) stores carbon 30% Decomposes slowly (biofuel)Seedless vascular plants1. Phyla: Lycophyta (club mosses, spike mosses and quillworts)2. Pterophyta (ferns, horsetails, whisk ferns)- Sporophytes are free-living and dominant form in life cycle; gametophyte is reduced- Xylem and phloem cells transport water and materials- Phloem- moves carbs around plant- Xylem- water conducting- Phloem and xylem make it so that the plant doesn’t need diffusion for transportationSporophyll and spore variations- Sporophylls- modified leaves with sporangia- Sori- clusters of sporangia on the undersides of sporophylls- Strobili -cone-like structures formed from groups of sporophyllsLycophyta (seedless vascular)- Spores club moss- used for gun powder in Civil WarPterophyta- Most diverse seedless vascular plants- overtopping growth- megaphylls- Branching along length of roots- Contain silicaField horsetail- silica = more
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