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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). - PowerPoint PPT Presentation
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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.
HaploidDiploid MEIOSIS
FERTILIZATION
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 conesa. Also called male cones.b. Produces the male
gametophytes, which are called pollen grains.
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
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. 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.
5. Developmenta. Fertilization produces a
zygote which grows into an
embryob. The embryo becomes
enclosed in a seed
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)
Filament Anther Style Stigma
Ovary
Petal
OvuleSepal
Stamen Pistil
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
2. Petalsa. Brightly colored and found
just inside the sepalsb. Attract insects and other
pollinators to the flower
3. Stamensa. Produce male
gametophytes – pollen grains
b. Consists of anther and filament
4. Carpelsa. Also called pistilsb. produce female
gametophytes – eggsc. Consists of ovary, style,
and stigma
D. Life Cycle of Angiosperms1. Reproduction in angiosperms
takes place within the flower2. Following pollination and
fertilization, the seeds develop inside protective structures
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.
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.
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 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.
http://www.youtube.com/watch?v=bwCpQflmQG4
http://www.youtube.com/watch?v=zVNsCW6eiiw
B. Seed Dispersal1. 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 light weight, allowing them to be carried in the air or to float to the surface of the water.
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.
D. Seed Germination- The early growth stage of the
plant embryo