Bio1151 Chapter 30 9
  1. Seed plants continued the evolution of smaller                 in the                of generations.
    • Some medicines derived from seed plants.

      Seed plants provide many products including food, wood, and many medicines.


    • Seed plant evolution.

      Bryophyte life cycles are dominated by gametophytes.

      Seedless vascular plants have sporophyte-dominated life cycles, with small, free-living gametophytes.

      Gametophyte reduction continued in seed plants, becoming microscopic and dependent upon the sporophyte for nutrition and protection.

     
  2. Gymnosperms bear "naked"         , typically on         .
     
  3. The gymnosperm life cycle shows a dominant               generation, and the development of          from fertilized          .
    • Gymnosperm life cycle.

    • Sporophytes bear cones.
    • Pollen cones contain microsporangia.
    • Ovulate cones contain megasporangia.
    • After pollination, a megaspore develops into a female gametophyte.
    • The pollen grain germinates a sperm cell which fertilizes an egg.
    • The ovule becomes a seed.

      Review and exercise:


    • In a pine, pollen cones contain microsporangia where microsporocytes undergo meiosis to produce microspores.

      Microspores develop into male gametophytes (pollen grains) by mitosis.


    • In a pine's ovulate cones, an ovule containing a megasporangium is surrounded by a protective integument.

      Upon pollination (transfer of pollen grain to ovule), the megasporangium produces megaspores by meiosis.


    • A pollen grain (male gametophyte) enters the female gametophyte through the micropyle of the ovule.

      It discharges a sperm which enters the female gametophyte.


    • The male gametophyte develops a pollen tube through which the sperm travels to the egg to produce a zygote.

      The pollen tube eliminates the need for sperm to swim and allows adaptation to dry environments.


    • Gymnosperm seed.

      After fertilization, the zygote becomes an embryo by mitosis. and the ovule develops into a seed.

      A seed consists of an embryo along with its food supply packaged in a protective seed coat derived from the integument.

     
  4. Angiosperms are seed plants that possess reproductive structures called            and          .

     
    • A flower is a specialized          with modified leaves and may produce fruits.
      • A flower may comprise four organs:


      • Sepals enclose the flower.
      • Petals may be brightly colored to attract pollinators.
      • Stamens (composed of anther and filament) produce pollen.
      • Carpels are (composed of stigma, style, and ovary.

        An ovary contains several ovules which develop into seeds after fertilization.


      • Fruit types.

        A fruit consists of a fertilized ovary (within its carpel) with one or more seeds.

        Fleshy fruits (tomato, grapefruit, nectarine) attract animals which eat the fruit and aid in dispersal of the indigestible seeds.

        Dry fruits (milkweed, hazelnut) are often adapted for dispersal by wind or water, or by animal carriers.

        Bat and agouti;

       
    • Fruits are adapted for seed              to new locations.

    • Seed dispersal.

      "Wings" enable a maple fruit (samara, or "helicopter") to be carried by the wind.

      Seeds within berries and other fruits are dispersed in animal feces.

      The barbs of cockleburs facilitate seed dispersal by allowing the fruits to "hitchhike" on animals.



    • The Swiss engineer George deMestral invented Velcro in 1948 when he noticed cockleburs stuck tightly to his pants as well as to his dog's fur, due to tiny hooks on the fruit that entangled into loops of thread or fur.
     
  5. The angiosperm life cycle includes a           fertilization which produces a food-storing              in addition to the          .
    • Angiosperm life cycle.

    • Anthers contain microsporangia which produce microspores by meiosis.
    • Microspores form male gametophytes (pollen grains) by mitosis.
    • Ovaries contain ovules where megasporangia produce megaspores by meiosis
    • Megaspores form female gametophytes (embryo sacs) by mitosis.
    • After pollination, double fertilization occurs.
    • The diploid zygote develops into an embryo within a seed.
    • A seed uses the triploid endosperm as food to germinate into a large sporophyte.

      Review and exercise:


    • Double fertilization in an Angiosperm. After reaching the ovule via the pollen tube, two sperm enter the female gametophyte (embryo sac). One sperm fertilizes an egg to form a zygote, the other fuses with 2 nuclei of a central cell to form a triploid endosperm. Review:
     
  6. Most angiosperms are             and            , classified by the number of               (seed leaves).
    • Monocot characteristics:


    • One cotyledon
    • Parallel leaf veins
    • Stem vascular tissue scattered
    • Floral organs usually in multiples of three

      Eudicot characteristics:


    • Two cotyledons
    • Net-like leaf veins
    • Stem vascular tissue arranged in ring.
    • Floral organs usually in multiples of four or five

      Which is this ? ?

      How about this:

     
    Review activity: