Ch 24 reproduction of seed plants
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Ch. 24- Reproduction of Seed Plants PowerPoint PPT Presentation

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Ch. 24- Reproduction of Seed Plants. Haploid Diploid. I. Reproduction With Cones and Flowers A. Alternation of Generations - All plants have a life cycle in which a diploid sporophyte generation alternates with a haploid gametophyte generation. MEIOSIS. Gametophyte Plant (N).

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Ch. 24- Reproduction of Seed Plants

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Ch. 24- Reproduction of Seed Plants



  • I. Reproduction With Cones and Flowers

    • A. Alternation of Generations

      • - All plants have a life cycle in which a diploid sporophyte generation alternates with a haploid gametophyte generation.


Gametophyte Plant (N)

Sporophyte Plant (2N)


  • B. Life Cycle of Gymnosperms

    • - Reproduction in gymnosperms takes place in cones, which are produced by a mature sporophyte plant.

    • 1. Pollen cones

      • a. Also called malecones.

      • b. Produces the male gametophytes, which are called pollengrains.

  • 2. Seed Cones

    • a. Produce female gametophytes

    • b. Much larger than pollen cones

    • c. At the base of each cone scale are found

      2 ovules in which the female gametophytes


  • 3. Pollination – The pollen is carried by the wind and caught on a sticky secretion (pollination drop) on one of the scales of the female cone.

  • 4. Fertilization

    • a. When a pollen grain lands near an ovule, it grows a pollentube into the ovule.

    • b. A sperm from the pollen tube fertilizes the egg in the ovule.

  • Development

    a. Fertilization produces a zygote

    which grows into an embryo

    b. The embryo becomes enclosed in a seed


  • C. Structure of Flowers

  • - Flowers are the reproductive organs that are composed of four kinds of specialized leaves: sepals, petals, stamens, and carpels. (Figure 24-5)











  • 1. Sepals

    • a. The outermost circle of floral parts contains the sepals, which in many plants are green and closely resemble ordinary leaves

    • b. Enclose bud and protect the flower during development

  • 2. Petals

    • a. Brightly colored and found just inside the sepals

    • b. Attract insects and other pollinators to the flower

  • 3. Stamens

    • a. Produce male gametophytes – pollen grains

    • b. Consists of anther and filament

  • 4. Carpels

    • a. Also called pistils

    • b. produce female gametophytes – eggs

    • c. Consists of ovary, style, and stigma

  • D. Life Cycle of Angiosperms

    • 1. Reproduction in angiosperms takes place within the flower

    • 2. Following pollination and fertilization, the seeds develop inside protective structures

  • E. Pollination

    • 1. Most gymnosperms and some angiosperms are wind pollinated, whereas most angiosperms are pollinated by animals.

    • 2. Insect pollination is more efficient than wind pollination, giving insect-pollinated plants a greater chance of reproductive success.

  • F. Fertilization in Angiosperms

    • 1. Double Fertilization – Inside the embryo sac, two distinct fertilizations take place

      • a. First, one of the sperm nuclei fuses with the egg nucleus to produce a diploid zygote, which will grow into the new plant embryo.

  • b. Second, the other sperm nucleus fuses with two polar nuclei in the embryo sac to form a triploid (3N) cell. This will grow into a food-rich tissue know as endosperm, which nourishes the seedling as it grows.

  • II. Seed Development and Germination

    • - the development of the seed, which provides protection and nutrition for the embryo, was a major factor in the success of plants on land.

  • A. Seed and Fruit Development

    • 1. As angiosperm seeds mature, the ovary walls thicken to form a fruit that encloses the developing seed.

    • 2. The term fruit, biologically speaking, applies to any seed that is enclosed within its embryo wall.



  • B. Seed Dispersal

    • 1. Dispersal by Animals- Seeds dispersed by animals are typically contained in fleshy, nutritious fruits.

  • 2. Dispersal by Wind and Water- Seeds dispersed by wind or water are typically lightweight, allowing them to be carried in the air or to float to the surface of the water.

  • C. Seed Dormancy

    • 1. Some seeds sprout rapidly while other seeds enter a period of dormancy, during which the embryo is alive but not growing.

    • 2. Environmental factors such as temperature and moisture can cause a seed to end dormancy and germinate.

  • D. Seed Germination

    • - The early growth stage of the plant embryo

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