UT Arlington BIOL BIOL 3427 - Gymnosperms (4 pages)

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This Lecture note describes the evolution of gymnosperms.

Lecture number:
Lecture Note
University of Texas at Arlington
Biol Biol 3427 - Plant Science

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BIOL 3427 1st Edition Lecture 14 Outline of Current Lecture II Prokaryotes III Viruses IV Fungi V Symbiotic relationships Current Lecture I Gymnosperms a Evolution of plants i Bryophytes ii Seedless vascular plants iii Seed plants 1 Gymnosperms 2 Angiosperms b Evolution of the seed i Why are seeds advantageous 1 Protects embryo 2 Stores food ii All seeds heterosporous iii Definition of seed 1 Fertilized mature ovule containing an embryo 2 Ovule a Nucellus megasporangium surrounded by 1 or 2 integuments with micropyle b Mature contains a megagametophte composed of archegonia and nutritive tissue c After fertilization integuments develop into seed coat d All seeds contain stored food iv Ovule evolution 7 events 1 Megaspore retained in megasporangium nucellus 2 Number of megaspore mother cells reduced to one 3 Only one of four megaspores survives 4 Megasporophyte highly reduced retained in megasporangium 5 Embryo young sporophyte develops within megasporophyte 6 Integument envelops megasporangium 7 Apex of megasporangium modified to receive pollen grains These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute II III IV V VI Fossil record a Unclear exact order of events above b Oldest seeds from late Devonian 365 mya i Gradually integuments fused until only opening left at apex micropyle c Five phyla of seed plants with living representatives i Seed plants typically possess megaphylls 1 Coniferophyta 2 Cyadophyta 3 Ginkophyta a Gymnosperms b Naked seeds c 840 species ii Modified into needles or scales in some groups a Gnetophya gymnosperms b Antherophyta angiosperms covered seed 300 000 species d Progymnosperms i Not gymnosperms 1 Extinct group of seedless vascular plants 2 Ancestors of seed plants were similar to progymnosperms ii Late Paleozoic iii In between trimerophytes and seed plants 1 Spores 2 Bifacial vascular cambium a Secondary xylem similar to conifers b

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