Ch. 24- Reproduction of Seed Plants
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Transcript of Ch. 24- Reproduction of Seed Plants
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Ch. 24- Reproduction of Seed Plants
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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.
HaploidDiploid MEIOSIS
FERTILIZATION
Gametophyte Plant (N)
Sporophyte Plant (2N)
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B. Life Cycle of Gymnosperms - Reproduction in gymnosperms
takes place in cones, which are produced by a mature sporophyte plant.
1. Pollen conesa. Also called male cones.b. Produces the male
gametophytes, which are called pollen grains.
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2. Seed Conesa. Produce female gametophytesb. Much larger than pollen conesc. At the base of each cone scale
are found 2 ovules in which the female gametophytes develop
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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.
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4. Fertilizationa. When a pollen grain lands
near an ovule, it grows a pollen tube into the ovule.
b. A sperm from the pollen tube fertilizes the egg in the ovule.
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5. Developmenta. Fertilization produces a
zygote which grows into an
embryob. The embryo becomes
enclosed in a seed
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ANGIOSPERMC. 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)
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Filament Anther Style Stigma
Ovary
Petal
OvuleSepal
Stamen Pistil
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1. Sepalsa. 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. Petalsa. Brightly colored and found
just inside the sepalsb. Attract insects and other
pollinators to the flower
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3. Stamensa. Produce male
gametophytes – pollen grains
b. Consists of anther and filament
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4. Carpelsa. Also called pistilsb. produce female
gametophytes – eggsc. Consists of ovary, style,
and stigma
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D. Life Cycle of Angiosperms1. Reproduction in angiosperms
takes place within the flower2. Following pollination and
fertilization, the seeds develop inside protective structures
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E. Pollination1. 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.
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F. Fertilization in Angiosperms1. Double Fertilization – Inside the
embryo sac, two distinct fertilizations take placea. 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.
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A. Seed and Fruit Development1. 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.
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http://www.youtube.com/watch?v=bwCpQflmQG4
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http://www.youtube.com/watch?v=zVNsCW6eiiw
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B. Seed Dispersal1. Dispersal by Animals- Seeds
dispersed by animals are typically contained in fleshy, nutritious fruits.
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2. Dispersal by Wind and Water- Seeds dispersed by wind or water are typically light weight, allowing them to be carried in the air or to float to the surface of the water.
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C. Seed Dormancy1. 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