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Chapter 29 Plant Diversity I: The Colonization of Land

Chapter 29 Plant Diversity I: The Colonization of Land. AP Biology. Requirements for Successful Life on Land. Supporting mechanism (vascular tissue, lignin) Absorptive structures (above & below ground) Conducting tissues (move fluids)

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Chapter 29 Plant Diversity I: The Colonization of Land

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  1. Chapter 29Plant Diversity I: The Colonization of Land AP Biology

  2. Requirements for Successful Life on Land • Supporting mechanism (vascular tissue, lignin) • Absorptive structures (above & below ground) • Conducting tissues (move fluids) • Anti-desiccation (drying out) adaptations for body of plant (cuticle) & gametes (pollen & spores) • Airborne gamete dispersal

  3. General Characteristics of Plants • Includes mosses, ferns, conifers, flowering plants • Multicellular, eukaryotic, photosynthetic autotroph • Chlorophyll a, b, and carotenoids • Cellulose • Starch

  4. General Characteristics of Plants, cont. • Alternation of generations (more next) • Most have stomata for gas exchange (Liverworts the exception) • Secrete cuticle to reduce desiccation • Most have vascular tissue for bulk transport of water and materials • Exchange of materials between adjacent cells through opening in cell walls (plasmodesmata) • Most have seeds (embryo with food & protective covering)

  5. Alternation of Generations • Gametes produced & protected within gametangia (non-reproductive cells to prevent desiccation & for protection) • Fertilization of egg takes place here (Female = archegonium; Male = antheridium)

  6. Alternation of Generations, cont. • Sporophyte & gametophyte are structurally (look & develop) different (heteromorphic) • Both structures are multicellular (unlike animals) • Sporophyte dominant in most species • Meiosis in sporophyte produces haploid reproductive cells (spores) • Spores can develop into a new organism without fusing with another cell

  7. Proposed Ancestors of Plants • Charophyceans are the green algae most related to land plants • Several lines of evidence support this including: • Homologous chloroplasts, cell walls, peroxisomes, sperm • Phragmoplasts – microtubules form perpendicular to cell plate and guide deposition of cellulose to form wall • Molecular systematics • Charophyceans had a layer of sporopollenin to prevent exposed zygotes from drying out until they are in water again

  8. Classified Into 2 Major Groups • Nonvascular plants (aka Bryophytes) • Bryophyta: mosses • Anthocrophyta: Hornworts • Heptophyta: Liverworts

  9. Vascular Plants (aka Tracheophytes) • Seedless vascular plants (Pteridophytes) • Lycophyta: Lycophytes • Pterophyta: Ferns & Horsetails

  10. Seeded vascular plants • Naked seeded plants (Gymnosperms) • Coniferophyta: Conifers • Cycadophyda: Cycads • Gnetophyta: Gnetae • Ginkgophyta: Ginko

  11. Flowering plants and enclosed seeds (Angiophyta) • Flowering plants

  12. Nonvascular Plants: Bryophytes • Gametophyte dominant form • Lack vascular tissues • Limits size (can’t grow tall) • Rely on diffusion • Rhizoids– analogous to roots; used for anchorage • Male flagellated sperm produced by the gametangium (antheridium) • Female egg produced by the gametangium (archegonium) • Sporophyte produces haploid spores within sporangium • 3 Divisions: • Bryophyta (mosses); ex: Sphagnum (peat moss) • Heptophyta (Liverworts); sexual and asexual reproduction • Anthocerophyta (hornworts)

  13. Vascular Plants: Tracheophytes • Key adaptations to success on land: • Seeds – protect embryo & provide food for initial growth • Pollen – airborne dispersal; Sporopollenin in walls of spores • Sporophyte dominant • Vascular tissues – phloem & xylem; specialization of parts of plant for specific functions (true roots, stems, and leaves) • Ligninfied cell walls – supports plant in air

  14. Seedless Vascular Plants • Division Lycophyta • Club mosses • Many are epiphytes – grow on other plants but not parasitic • Sporangia produced on specialized leaves for reproduction called sporophylls • Most species are homosporous – produce a single type of spore that can produce a gametophyte with antheridia and archegonia • Heterosporousspecies – have sporophytes that produce separate spores • Megaspores – produce female archegonia on female gametophyte • Microspores – produce male antherdia on male gametophyte

  15. Seedless Vascular Plants • Division Sphenophyta • Horsetail (Equisetum) – only extant genus • Homosporous • Silica in cell walls make stems abrasive • Gametophyte is free-living; can photosynthesize and not dependent on sporophyte for nutrients

  16. Seedless Vascular Plants • Division Pterophyta • Ferns – dominant seedless vascular plant • Large leaves (fronds) – compound with smaller leaflets • Leaves are megaphylls – leaves with branched vascular tissues/veins • Homosporous • Sporangia develop on specialized sporophylls • Sporangia grow in clusters (sori) on underside • Flagellated sperm – require water & fertilization of egg in archegonium • Sporophyte protected in archogonium and emerges from ground as fiddlehead

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