Gymnosperms and Angiosperms

Gymnosperms and Angiosperms

  • Continue the trend of reduction in the size of the gametophyte

  • The male gametophyte is pollen which has non-motile sperm inside, eliminating the need for water

  • Sperm travels by air or mutualistic relationships so it lives in drier habitats.

  • Advantages of seeds

    • Protect and nourish the embryo

    • Can remain dormant for a long time

    • Dispersal through wind, water, and animals

  • Sporopollenin - found away from water, farther inland. It’s sperm travel by wind/animal pollinators

  • Plant Embryo - Sporophyte, Seeds - Multicellular

  • Requirements of seed formation

    • Development of an ovule from the sporophyte​

    • Meiosis produces megaspores​ which form the female gametophyte

    • The egg develops and is fertilized in the gametophyte

    • Embryo produced by zygote​

    • Testa produced by the integument of the gametophyte nourishes the zygote​

  • Gymnosperms have naked or exposed seeds

    • Cycads: Class Cycadospida

      • Similar in appearance to palm trees

      • Seed cones

      • Flagellated sperm

      • Dioecious

  • Gnetophytes: Class Gnetopsida

    • Xylem has vessel elements

    • Can be trees, shrubs, or vines

    • Seed cones

    • Dioecious

    • Non-flagellated sperm

    • Welwitschia leaves can grow 13 feet long.

Ex - Ephedra and Welwitschia

  • Conifers: Class Pinopsida

    • Can be shrubs or trees, Needle-like or scaley leaves

    • Found in cold and dry environments, Seed cones, Monoecious

    • Lack of vessel elements in their xylem

    • Undergo secondary growth

    • Adaptive to fire -> Helps reproduce

    • Female cones are larger than male cones, Female cones at the top and male cones on lower branches -> helps prevent self-fertilization -> sperm won’t fall on female cones.

Angiosperms

  • Flowers grouped together → Inflorescence

  • A

  • B

  • Plants that produce both male and female sex organs (flowers) on the same plant → monoecious, aka Perfect flower

  • Imperfect flower - Male and female flowers on different plants → dioecious

  • Monocots usually have parallel veins, complexly arranged vascular bundles, a fibrous root system, and floral parts arranged in multiples of three.

  • Dicots usually have netlike veins, vascular bundles arranged in rings, a taproot system, and floral parts in multiples of four or five.

  • Double Fertilization - Two pollen create pollen tubes at the top of the stigma and enter to ovary, one pollen combines with an egg to create a zygote and then an embryo, and the other pollen combines with two polar nuclei to create a triploid endosperm nutritive coating which is used as food for the embryo.

  • Primary function of fruits in angiosperms → Seed dispersal