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Evolution of Land Plants: From Algae to Seed Plants

Learn the evolutionary journey of plants, from algae to seed-bearing species. Explore adaptations and life cycles, and understand the significance of seeds in plant success.

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Evolution of Land Plants: From Algae to Seed Plants

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  1. Chapter 29 and 30: Plants Objectives -Understand that land plants evolved from green algae -Mosses and other nonvascular plants have life cycles dominated by gametophytes -Ferns and other seedless vascular plants were the first plants to grow tall -Seeds and pollen grains are the key to success for land plants -Gymnosperms bear “naked” seeds (cones) -Reproductive adaptations of angiosperms include flowers and fruit

  2. Morphological and Molecular data suggests land plants evolved from green algae (Charophytes) Morphological Rossete shaped cellulose synthesizing proteins in plasma membrane Peroxisome enzymes that help minimize loss of organic products of metabolism from photorespiration Flagellated sperm Formation of a phragmoplast during cell division Genetic Sampling also indicates similarities

  3. 2. Production of protective spores Adaptations or derived characteristics that allowed plants to move to land. 1. Alternation of Generations -Has a multicelluar haploid and diploid organisms -Plants are called embryophtes due to the embryonic activity in the female gametophyte - Analogous to mammals 4. Use of an Apical meristem for elongation 3. Multicellular Gametangia (1n)

  4. Current Understanding of plant evolution

  5. Bryophyte refers to all Nonvascular plants -Gametophytes are longer and larger then Sporophyte Horwort Liverwort Mosses

  6. Seedless Vascular Plants -Sporophyte dominant -Contain Xylem, which brings water and minerals up from the roots ** Allows for strength in stem = growing tall -Contain Phloem for transport of organic compounds Sporophylls -Modified leaves that contain Sporangia -Homospores = one type of spore -Heterospore = male (microspore) and female spore (megaspore) Leaves divided into Microphylls (smalll) Megaphylls (large extensive leaves)

  7. Seedless Vascular Plants

  8. The importance and evolutionary significance of seeds as a derived characteristic • 1. 2n Embryo with its food supply • Means the embryo can survive away from mother plant • Analogous to a detachable woman’s womb • Dispersed in a variety of ways • Contributions to human society • Hunter/Gatherer • to • Settlers using agriculture

  9. Immergence of Seed plants • Reduced Gametophyte stage –Allows for protection of the gametophytes within the sporangia of the sporophyte = great success in seeded plants • Contain heterospores (Male and Female) • Seeds have advantages over spores (More protection, Food source, Can remain dormant longer, Stored food can help in germination)

  10. Development of seeds and pollination • Female (Megasporangium) is covered by a thin layer called integument • Megasporangium undergoes Meiosis and produces a Megaspore • Pollen is produced in a mircospore • Pollen doesn’t need water to swim in like Flagellated sperm of seedless plants (Wind or hitch hike) • Female Gametophyte grows • Male Gametophyte is in the pollen grain • 3. Pollination occurs (Pollen (1n) enters through an opening of the integument and fertilizes the egg • After fertilization the integument turnes into the seed coat • Embryo or new sporophyte begins to form

  11. Gymnosperms • - Naked seeds (No Fruit) • -Four Gymnosperm Phyla • Ginkgophyta • Coniferophyta • Cycadophyta • Gnetophyta

  12. Pollination occurs when pollen attaches to the Megaspore and germinates forming a pollen tube (digests its way through the Megasporangium) Conifers have both pollen and ovulate cones While pollen tube extends the Megaspore undergoes meiosis Microspores produce pollen grains that contain the gametophyte Usually takes about a year from pollination to seed and only one embryo usually survies

  13. Stamen produce microspores which turn in to pollen Carpel produces megaspores Angiosperms are flowering plants

  14. Fruits -Fruits are the ovary with the fertilized seed inside -Protect and aid in dispersion

  15. Some flowers self pollinate while most have mechanisms to cross pollinate Double fertilization produces endosperm or nutrients -Possible reason is to synchronize development of food sources and seed 4 megaspores are formed with one surviving

  16. Monocots Eudicots Basil Angiosperms Magnoliids

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