Bio1151 Chapter 29 Plant Diversity I: How Plants Colonized Land
  1. Land plants ( kingdom          ) are a diverse group that evolved from        algae.

    Plant evolution. Kingdom Plantae comprises 7 major clades classified into 10 phyla.

    Plant phyla.

    Anthophyta (or Angiosperms, the flowering plants) is the most recently evolved, and most diverse, of the 10 plant phyla.

    Kingdom Plantae (Embryophytes) are multicellular, photosynthetic eukaryotes, adapted to life on dry land.

    They are most closely related to the Charophytes, which is a branch off the Chlorophyta (green algae).

      Green algae called charophytes are the closest living algal relatives of land plants.
  2. Four innovations among the kingdom Plantae are:
    • Alternation of              , with multicellular, dependent          .

      Plantae alternation of generations.

      Multicellular, haploid gametophytes produce haploid gametes by mitosis.

      Fertilization of egg and sperm form a diploid zygote, which undergoes mitosis to produce the diploid sporophyte.

      A mature sporophyte may undergo meiosis to produce haploid spores, which can germinate into a haploid gametophytes by mitosis.

      Multicellular embryos.

      Multicellular plant embryos develop from zygotes within tissues of the female parent.

      The parent provides nutrients to dependent embryos through placental transfer cells.

    • Multicellular            which produce spores.


      A diploid sporophyte of this moss contains organs called sporangia.

      The sporangia cells undergo meiosis to generate haploid spores.

    • Multicellular             which produce gametes.


      A liverwort produces male and female gametangia on separate plants.

      Female gametangia, called archegonia, produce eggs.

      Male gametangia, called antheridia, produce and release sperm.

    • Apical            in root and shoot systems.

    Apical meristems provide regions of continual growth in plants.

    Light and carbon dioxide are above ground, while water and minerals are in the soil.

    The apical meristems in shoots and roots allow elongation of the plant to reach these resources.

  3. Bryophytes lack           tissue with three phyla of small herbaceous plants.

    Bryophytes lack vascular tissues.

    These small herbaceous (non-woody) plants live in moist habitats.

    The three phyla are:

    A) Liverworts (Hepatophyta)

    B) Hornworts (Anthocerophyta)

    C) Mosses (Bryophyta)

    Note the small sporophytes growing on the larger gametophytes.

    Sphagnum moss, a bryophyte..

    Note the large,photosynthetic gametophytes and the smaller sporophytes of this bryophyte.

    The plants release acid as they grow, building "peat bogs" after many generations.

      The acid in peat bogs slows down decay of organic materials.

    • Dead Sphagnum moss can accumulate in deep layers in these bogs and are harvested for fuel and as a soil conditioner.
    • This "Tollund Man" has been preserved since the 4th century BC in Denmark.
    • The large gametophytes produce          which fuse to yield small              .

      Bryophyte gametangia.

      The large, "leafy" photosynthetic gametophytes of a moss contain gametangia.

      Gametophytes do not have roots; they are anchored by rhizoids.

    • Sporophytes produce haploid         which grow to become the               .

    Bryophyte life cycle.

  4. Spores develop into haploid protonemata.
  5. Protonemata produce "buds" that undergo mitosis.
  6. Buds develop into gametophyte bearing antheridia or archegonia.
  7. Sperm swims to egg in archegonium.
  8. Fertilized diploid zygote develops into sporophyte embryo.
  9. Sporophyte emerges from the archegonium.
  10. The small sporophyte is dependent on the large gametophyte.
  11. Spores develop by meiosis in sporangium.

    Review and exercise:

  12. Vascular plants possess specialized vascular tissues called        and         .

    Vascular plants possess vessels (xylem and phloem) that transport water and nutrients. Roots allow them to extract water from the soil; vascular tissue also provide strength to support a larger body. Early vascular did not reproduce via seeds and are called seedless.
  13. Seedless vascular plants have life cycles with dominant              and form two phyla.

    Fern life cycle.

  14. Sporangia release spores.
  15. Spore develops into a small, bisexual, photosynthetic gametophyte.
  16. Gametophyte produces sperm in antheridia and eggs in archegonia.
  17. Sperm swim to eggs in archegonia.
  18. Zygote develops into large sporophyte.
  19. Clusters of sporangia form in sori.

    Review and exercise:

    • Lycophyta includes       mosses,        mosses, and             .

      Phylum Lycophyta

      Spike mosses are small with simple, scale-like leaves.

      Quillworts are a single genus that lives in marshy areas.

      Club mosses have sporophylls (modified leaves with sporangia) clustered into club-shaped cones (strobili).

    • Pterophyta includes        ,             , and        ferns and their relatives.

      Phylum Pterophyta Ferns have large leaves; the sporophylls bear sori (clusters of sporangia). Horsetail stems have a gritty texture and some have been used as "scouring rushes" for pots and pans. Whisk ferns form fused sporangia on stems seen here as yellow knobs.
    • Seedless vascular plants grew to great heights during the                period and may have led to global cooling.

    The first vascular forests flourished in the Carboniferous period, about 300 million years ago

    The growth of giant lycophytes and tree ferns reduced atmospheric CO[2]levels, leading to global cooling at the end of the Carboniferous.