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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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slide2

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)

Sporophyte Plant (2N)

FERTILIZATION

slide3

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.
slide4

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

develop

slide5

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.

slide6

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.
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Development

a. Fertilization produces a zygote

which grows into an embryo

b. The embryo becomes enclosed in a seed

angiosperm
ANGIOSPERM
  • 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)
slide9

Pistil

Stamen

Style

Stigma

Anther

Filament

Ovary

Petal

Sepal

Ovule

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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
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2. Petals

      • a. Brightly colored and found just inside the sepals
      • b. Attract insects and other pollinators to the flower
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3. Stamens

      • a. Produce male gametophytes – pollen grains
      • b. Consists of anther and filament
slide13

4. Carpels

      • a. Also called pistils
      • b. produce female gametophytes – eggs
      • c. Consists of ovary, style, and stigma
slide14

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
slide15

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.
slide16

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.
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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.

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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.
slide20

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.
slide24

B. Seed Dispersal

      • 1. Dispersal by Animals- Seeds dispersed by animals are typically contained in fleshy, nutritious fruits.
slide25

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.

slide27

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.
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D. Seed Germination

      • - The early growth stage of the plant embryo
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