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The Plant Kingdom: Seedless Plants

The Plant Kingdom: Seedless Plants

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The Plant Kingdom: Seedless Plants

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  1. The Plant Kingdom:Seedless Plants Chapter 27

  2. Learning Objective 1 • What are some environmental challenges of living on land? • How do some plant adaptations meet these challenges?

  3. Colonization of Land by Plants • Required anatomical, physiological, and reproductive adaptations • Waxy cuticle • protects against water loss • Stomata • for gas exchange needed for photosynthesis

  4. Alternation of Generations1 • 2 parts of plant life cycle • haploid gametophyte generation • diploid sporophyte generation • Gametophyte plant • produces gametes by mitosis • gametes fuse (fertilization) to form zygote (first stage of sporophyte generation)

  5. Basic Plant Life Cycle

  6. Gametophyte Spore Sperm Egg HAPLOID (n) GAMETOPHYTE GENERATION Meiosis Fertilization DIPLOID (2n) SPOROPHYTE GENERATION Zygote Embryo Sporophyte Fig. 27-2, p. 582

  7. Gametophyte Spore Sperm Egg HAPLOID (n) GAMETOPHYTE GENERATION Meiosis Fertilization DIPLOID (2n) SPOROPHYTE GENERATION Zygote Embryo Sporophyte Stepped Art Fig. 27-2, p. 582

  8. Alternation of Generations2 • Zygote develops into multicellular embryo • protected and nourished by gametophyte • Mature sporophyte plant • develops from the embryo • produces sporogenous cells (spore mother cells)

  9. Alternation of Generations3 • Sporogenous cells undergo meiosis to form spores • first stage in gametophyte generation

  10. KEY CONCEPTS • Plants undergo an alternation of generations between multicellular gametophyte and sporophyte generations

  11. Gametangia 1 • Most plants have multicellular gametangia • with protective jacket of sterile cells surrounding gametes

  12. Gametangia 2 • Antheridia • gametangia that produce sperm cells • Archegonia • gametangia that produce eggs

  13. Gametangia

  14. Developing sperm cells Sterile cells Antheridium Fig. 27-3a, p. 583

  15. Egg Archegonium Sterile cells Fig. 27-3b, p. 583

  16. Vascular Transport System • In ferns and other vascular plants • xylem conducts water and dissolved minerals • phloem conducts dissolved sugar

  17. KEY CONCEPTS • Adaptations to life on land that have evolved in plants include a waxy cuticle to prevent water loss; multicellular gametangia; stomata; and for most plants, vascular tissues containing lignin

  18. Learning Objective 2 • From which green algal group are plants hypothesized to have descended? • Describe supporting evidence

  19. Charophytes • Plants probably arose from charophytes • a group of green algae • Based on molecular comparisons of DNA and RNA sequences • close match between charophytes and plants

  20. Plant Evolution

  21. VASCULAR SEEDLESS PLANTS NONVASCULAR BRYOPHYTES VASCULAR SEED PLANTS Gymnosperms Angiosperms Club mosses Hornworts Liverworts Mosses Ferns Evolution of seeds Evolution of dominant sporophyte, vascular tissue Evolution of cuticle, multicellular gametangia, multicellular embryos Green algal ancestor Fig. 27-4, p. 584

  22. KEY CONCEPTS • Biologists infer that plants evolved from aquatic green algal ancestors known as a charophytes

  23. Insert “Evolutionary tree for plants” plant_tree_v2.swf

  24. Explore plant evolution by clicking on the figure in ThomsonNOW.

  25. Learning Objective 3 • What features distinguish bryophytes from other plants?

  26. Bryophytes • Nonvascular (lack xylem and phloem) • unlike other land plants • Dominant gametophyte generation • unlike other plants • Sporophytes remain permanently attached • nutritionally dependent on gametophytes

  27. Learning Objective 4 • What are the three phyla of bryophytes?

  28. Mosses (Phylum Bryophyta) • Gametophytes are green plants that grow from a filamentous protonema

  29. Liverworts (Phylum Hepatophyta) • Many gametophytes are flattened, lobelike thalli (others are leafy)

  30. Hornworts(Phylum Anthocerophyta) • Have thalloid gametophytes

  31. Fig. 27-5, p. 585

  32. Vascular seedless plants Nonvascular bryophytes Vascular seed plants Green algal ancestor Fig. 27-5 (1), p. 585

  33. KEY CONCEPTS • Mosses and other bryophytes lack vascular tissues and do not form true roots, stems, or leaves

  34. Learning Objective 5 • Describe the life cycle of mosses • Compare their gametophyte and sporophyte generations

  35. Mosses 1 • Green moss gametophyte • bears archegonia / antheridia at top of plant • Fertilization • sperm cell fuses with egg cell in archegonium (zygote)

  36. Mosses 2 • Zygote • grows into embryo • develops into moss sporophyte attached to gametophyte

  37. Mosses 3 • Meiosis • occurs within capsule of sporophyte • produces spores • When spore germinates • grows into a protonema • forms buds that develop into gametophytes

  38. Moss Life Cycle

  39. Antheridia at the tip of the gametophyte shoot Gametophyte plants Buds on protonema 1 Antheridia with sperm cells Spore germinates Spores released 6 Protonema Sperm cell HAPLOID (n) GAMETOPHYTE GENERATION 2 Archegonium with egg Fertilization Meiosis DIPLOID (2n) SPOROPHYTE GENERATION 5 Calyptra Zygote Capsule 4 3 Sporogenous cells that undergo meiosis Sporophyte Embryo Gametophyte plant Fig. 27-6, p. 586

  40. Moss Sporophytes

  41. Capsule Seta Foot Fig. 27-7, p. 587

  42. Liverwort Life Cycle

  43. Antheridiophore Archegoniophore Male thallus Germination of spores and development of young gametophyte 1 Antheridia with sperm cells Female thallus 5 Gemmae cup Spores released Sperm cell Male and female gametophyte plants HAPLOID (n) GAMETOPHYTE GENERATION Archegonia with eggs 2 Fertilization Meiosis DIPLOID (2n) SPOROPHYTE GENERATION 4 Foot Seta Zygote Tissue derived from archegonium Embryo Capsule Sporogenous cells that undergo meiosis 3 Sporophyte Fig. 27-8, p. 588

  44. Insert “Moss life cycle” moss_life_cycle_v2.swf

  45. Insert “Marchantia, a liverwort” liverwort.swf

  46. Watch the life cycles of the mosses and liverworts by clicking on the figures in ThomsonNOW.

  47. Learning Objective 6 • What features distinguish seedless vascular plants from algae and bryophytes?

  48. Seedless Vascular Plants • Have adaptations that algae and bryophytes lack • vascular tissues • dominant sporophyte generation • Reproduction depends on water • as transport medium for motile sperm cells (as in bryophytes)

  49. Learning Objective 7 • What are the two phyla of seedless vascular plants?

  50. Club Mosses (Phylum Lycopodiophyta) • Sporophytes consist of roots, rhizomes, erect branches, and microphylls (leaves)