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Seed Formation in Gymnosperms & Angiosperms

Seed Formation in Gymnosperms & Angiosperms. Fig. 30-2a. Mosses and other nonvascular plants. Gametophyte. Dominant. Reduced, dependent on gametophyte for nutrition. Sporophyte. Sporophyte (2 n ). Gametophyte ( n ). Example. Fig. 30-2b. Ferns and other seedless vascular plants.

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Seed Formation in Gymnosperms & Angiosperms

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  1. Seed Formation in Gymnosperms & Angiosperms

  2. Fig. 30-2a Mosses and othernonvascular plants Gametophyte Dominant Reduced, dependent ongametophyte for nutrition Sporophyte Sporophyte(2n) Gametophyte(n) Example

  3. Fig. 30-2b Ferns and other seedlessvascular plants Reduced, independent(photosynthetic andfree-living) Gametophyte Dominant Sporophyte Sporophyte(2n) Example Gametophyte(n)

  4. Fig. 30-2c Seed plants (gymnosperms and angiosperms) Reduced (usually microscopic), dependent on surroundingsporophyte tissue for nutrition Gametophyte Dominant Sporophyte Gymnosperm Angiosperm Microscopic femalegametophytes (n) inside ovulate cone Microscopic femalegametophytes (n) insidethese partsof flowers Microscopic malegametophytes (n) insidethese partsof flowers Example Microscopic malegametophytes (n) inside pollencone Sporophyte (2n) Sporophyte (2n)

  5. Fig. 30-2 PLANT GROUP Mosses and othernonvascular plants Ferns and other seedlessvascular plants Seed plants (gymnosperms and angiosperms) Reduced, independent(photosynthetic andfree-living) Reduced (usually microscopic), dependent on surroundingsporophyte tissue for nutrition Gametophyte Dominant Reduced, dependent ongametophyte for nutrition Sporophyte Dominant Dominant Gymnosperm Angiosperm Sporophyte(2n) Microscopic femalegametophytes (n) insideovulate cone Microscopic femalegametophytes (n) insidethese partsof flowers Sporophyte(2n) Gametophyte(n) Example Microscopic malegametophytes (n) insidethese partsof flowers Microscopic malegametophytes (n) inside pollencone Sporophyte (2n) Sporophyte (2n) Gametophyte(n)

  6. Pollen and Production of Sperm • Microspores develop into pollen grains, which contain the male gametophytes • Pollination is the transfer of pollen to the part of a seed plant containing the ovules • Pollen eliminates the need for a film of water and can be dispersed great distances by air or animals • If a pollen grain germinates, it gives rise to a pollen tube that discharges two sperm into the female gametophyte within the ovule

  7. The Evolutionary Advantage of Seeds • A seed is a sporophyte embryo, along with its food supply, packaged in a protective coat • Seeds provide some evolutionary advantages over spores: • They may remain dormant for days to years, until conditions are favorable for germination • They may be transported long distances by wind or animals

  8. Fig. 30-6-1 Key Haploid (n) Diploid (2n) Pollencone Microsporocytes(2n) Maturesporophyte(2n) Pollengrains (n) MEIOSIS Microsporangia Microsporangium (2n)

  9. Fig. 30-6-2 Key Haploid (n) Ovule Diploid (2n) Ovulatecone Megasporocyte (2n) Integument Pollencone Microsporocytes(2n) Megasporangium(2n) Maturesporophyte(2n) Pollengrain Pollengrains (n) MEIOSIS MEIOSIS Microsporangia Microsporangium (2n) Survivingmegaspore (n)

  10. Fig. 30-6-3 Key Haploid (n) Ovule Diploid (2n) Ovulatecone Megasporocyte (2n) Integument Pollencone Microsporocytes(2n) Megasporangium(2n) Maturesporophyte(2n) Pollengrain Pollengrains (n) MEIOSIS MEIOSIS Microsporangia Microsporangium (2n) Archegonium Femalegametophyte Spermnucleus (n) Pollentube FERTILIZATION Egg nucleus (n)

  11. Fig. 30-6-4 Key Haploid (n) Ovule Diploid (2n) Ovulatecone Megasporocyte (2n) Integument Pollencone Microsporocytes(2n) Megasporangium(2n) Maturesporophyte(2n) Pollengrain Pollengrains (n) MEIOSIS MEIOSIS Microsporangia Microsporangium (2n) Survivingmegaspore (n) Seedling Archegonium Femalegametophyte Seeds Foodreserves(n) Spermnucleus (n) Seed coat(2n) Pollentube Embryo(2n) FERTILIZATION Egg nucleus (n)

  12. Fig. 30-3-3 Seed coat(derived fromintegument) Food supply(femalegametophyte tissue) Embryo (2n)(new sporophyte) (c) Gymnosperm seed

  13. Angiosperms • Angiosperms are seed plants with reproductive structures called flowers and fruits • They are the most widespread and diverse of all plants

  14. Flowers • The flower is an angiosperm structure specialized for sexual reproduction • Many species are pollinated by insects or animals, while some species are wind-pollinated

  15. A flower is a specialized shoot with up to four types of modified leaves: • Sepals, which enclose the flower • Petals, which are brightly colored and attract pollinators • Stamens, which produce pollen on their terminal anthers • Carpels, which produce ovules

  16. Fig. 30-7 (Female) (Male) Stigma Carpel (or Pistil) Stamen Anther Style Filament Ovary Petal Sepal Ovule

  17. A carpel (or pistil) consists of an ovary at the base and a style leading up to a stigma,where pollen is received Video: Flower Blooming (time lapse)

  18. Fruits • A fruit typically consists of a mature ovary but can also include other flower parts • Fruits protect seeds and aid in their dispersal • Mature fruits can be either fleshy or dry Animation: Fruit Development

  19. Fig. 30-8 Tomato Ruby grapefruit Nectarine Hazelnut Milkweed

  20. Various fruit adaptations help disperse seeds • Seeds can be carried by wind, water, or animals to new locations

  21. Fig. 30-9 Wings Seeds within berries Barbs

  22. The Angiosperm Life Cycle • The flower of the sporophyte is composed of both male and female structures • Male gametophytes are contained within pollen grains produced by the microsporangia of anthers • The female gametophyte, or embryo sac, develops within an ovule contained within an ovary at the base of a stigma • Most flowers have mechanisms to ensure cross-pollination between flowers from different plants of the same species

  23. The Angiosperm Life Cycle (cont) • A pollen grain that has landed on a stigma germinates and the pollen tube of the male gametophyte grows down to the ovary • The ovule is entered by a pore called the micropyle • Double fertilization occurs when the pollen tube discharges two sperm into the female gametophyte within an ovule

  24. The Angiosperm Life Cycle (cont) • One sperm fertilizes the egg (now a zygote (2n)), while the other combines with two nuclei in the central cell of the female gametophyte and initiates development of food-storing endosperm (3n) • The endosperm nourishes the developing embryo • Within a seed, the embryo consists of a root and two seed leaves called cotyledons

  25. Fig. 30-10-1 Key Haploid (n) Diploid (2n) Microsporangium Anther Microsporocytes (2n) Mature flower onsporophyte plant(2n) MEIOSIS Generative cell Microspore(n) Tube cell Male gametophyte(in pollen grain)(n) Pollengrains

  26. http://bio.rutgers.edu/~gb101/lab8_angio_repro/8a3m-microgpyt.htmlhttp://bio.rutgers.edu/~gb101/lab8_angio_repro/8a3m-microgpyt.html Each microspore divides by mitosis to form two haploid nuclei (the tube nucleus and the generative nucleus); A diploid microsporocyte, or microspore mother cell, divides to give rise to four haploid microspores. After landing on the stigma, the pollen germinates forming a pollen tube; the generative nucleus then divides by mitosis to form two haploid sperm nuclei.

  27. Fig. 30-10-2 Key Haploid (n) Diploid (2n) Microsporangium Anther Microsporocytes (2n) Mature flower onsporophyte plant(2n) MEIOSIS Generative cell Microspore(n) Ovule (2n) Tube cell Male gametophyte(in pollen grain)(n) Ovary Pollengrains MEIOSIS Megasporangium(2n) Megaspore(n) Antipodal cellsCentral cell (or polar bodies that form endosperm)SynergidsEgg (n) Female gametophyte(embryo sac)

  28. http://bio.rutgers.edu/~gb101/lab8_angio_repro/8a3m-microgpyt.htmlhttp://bio.rutgers.edu/~gb101/lab8_angio_repro/8a3m-microgpyt.html The remaining megaspore nucleus undergoes three mitotic divisions to form eight haploid nuclei. A diploid megasporocyte (megaspore mother cell) undergoes meiosis, giving rise to four haploid megaspore nuclei (3 of which disintegrate). Nuclear migration and cytokinesis occur to form the mature megagametophyte

  29. Fig. 30-10-3 Key Haploid (n) Diploid (2n) Microsporangium Anther Microsporocytes (2n) Mature flower onsporophyte plant(2n) MEIOSIS Generative cell Microspore(n) Ovule (2n) Tube cell Male gametophyte(in pollen grain)(n) Ovary Pollengrains MEIOSIS Stigma Megasporangium(2n) Pollentube Sperm Megaspore(n) Style Antipodal cellsCentral cellSynergidsEgg (n) Female gametophyte(embryo sac) Pollentube Sperm(n) FERTILIZATION Eggnucleus (n) Discharged sperm nuclei (n)

  30. Fig. 30-10-4 Key Haploid (n) Diploid (2n) Microsporangium Anther Microsporocytes (2n) Mature flower onsporophyte plant(2n) MEIOSIS Generative cell Microspore(n) Ovule (2n) Tube cell Male gametophyte(in pollen grain)(n) Ovary Pollengrains MEIOSIS Germinatingseed Stigma Megasporangium(2n) Pollentube Embryo (2n)Endosperm (3n)Seed coat (2n) Sperm Seed Megaspore(n) Style Antipodal cellsCentral cellSynergidsEgg (n) Female gametophyte(embryo sac) Pollentube Sperm(n) Nucleus ofdevelopingendosperm(3n) FERTILIZATION Zygote (2n) Eggnucleus (n) Discharged sperm nuclei (n)

  31. Practice!!! • http://bio.rutgers.edu/~gb101/lab8_angio_repro/index.html

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