9- The Crown Group Kingdoms

9- The Crown Group Kingdoms - BIOL 112 K. Auf., 7/07...

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BIOL 112 K. Auf., 7/07 Systematics of the Higher Eukaryotes The “Crown Group” The Kingdoms Plantae, Fungi and Animalia are called the “Crown Group” kingdoms of the Domain Eukarya. All contain multicellular organisms with an advanced organization of the body plan. All of them make extensive use of the alternation of generations eukaryotic sexual reproduction system (the X-scheme), but individual Kingdoms spend more or less time in certain phases of the haplo- and diplophase alternation life cycle. Kingdom Plantae Multicellular, mostly macroscopic forms which are mostly photoautotrophic, with cell walls contining cellulose. True multicellular forms with more than one tissue type in the body; highly organized tissues assembled into stereotyped structures: stems, leaves and roots. Some species in the kingdom vascularized (xylem and phloem). Most species are terrestrial or secondarily aquatic. At least 500,000 species. Plants appear to have evolved from the green algae (P. Chlorophyta) and the charophytes some 400 × 10 6 years ago. As one compares primitive to advanced plants, one see a number of important evolutionary trends: (1) increasing complexity of organization of the body, (2) increasing importance of the diploid phase of the life cycle, and (3) increasing independence from need for free water film for general life cycle and especially for fertilization. Some schemes suggest that the chlorophytes, charophytes and the plants could be combined into a proposed Kingdom Viridiplantae. This would provide a full evolutionary lineage of a group of photosynthetic organisms. Cryptogams (seedless plants) The primitive phyla in the K. Plantae were mysteries to early botanists. The plants did not produce seeds, so it was not apparent how they proliferated. We now know that these organisms release microscopic spores which germinate into gametophytes. But the informal category of cryptogams (“hidden gametes”) for the seedless plants (bryophytes, ferns and other groups) still persists. Phylum Bryophyta (mosses) Primitive plants, live in moist environments. Haploid (gametophyte) dominant life cycle, but both gametophyte and sporophyte generations are multicellular. Poor multicellular organization, no vascularization of tissues. Dimorphic gametophytes: males produce sperm in antheridia; females produce eggs in archegonia. Sperm are poor swimmers and depend upon splash (rain drops) to be moved to vicinity of the archegonia. Sperm can then swim short distances to the archegonial opening. Sporophyte is non-photosynthetic and depends upon parent gametophyte for nourishment and support. Mature sporophytes generate sporangia.
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2 Inside the sporangium, meiosis and sporulation takes place, producing haploid spores. These are dispersed from the sporangium and each spore can germinate into a new gametophyte. Mosses and liverworts differ from algae in that both have extended multicellular
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This note was uploaded on 03/27/2008 for the course BIOL 112 taught by Professor Vaughn during the Spring '08 term at Texas A&M.

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9- The Crown Group Kingdoms - BIOL 112 K. Auf., 7/07...

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