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Alternation

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by

Katelynn Dorn

on 2 May 2014

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Transcript of Alternation

Flowers
& Their Structure
Gymnosperms
Pollen Cones & Seed Cones
Gymnosperms
Pollination
Gymnosperms
Fertilization and Development
Pollination
Alternation
of Generations
in Angiosperms
some are wind-pollinated, most are animal-pollinated
insects, birds, bats
Fertilization
in Angiosperms
pollen grain lands on stigma and produces pollen tube
2 FERTILIZATIONS- DOUBLE THE FUN!!!!!!
one sperm nuclei fuses with egg nucleus to produce diploid zygote, which becomes new plant embryo
other sperm fuses with 2 polar nuclei in embryo sac to create endosperm (3N)- food for seedling
double fertilization
Angiosperms
Life Cycle
Cells in anther undergo meiosis and produce 4 haploid spore cells
pollen grain walls thicken to protect against dryness and physical damage (Matthew 6:28-29)
in ovary, diploid cell undergoes meiosis to produce 4 haploid cells, and 3 disintegrate
The remaining cell undergoes meiosis to make 8 nuclei in embryo sac- this is the female gametophyte.
One of the 8 nuclei is the egg nucleus, which will become zygote when fertilized.
Reproduction with Cones & Flowers, 24-1
gametophyte & sporophyte stage
sporophyte- plant we recognize
gametophyte- in cones and flowers
evolutionists will say that as the gametophyte size decreased, the sporophyte size increased
pollen cones- male, seed cones- female
2 ovules at base of each scale where female gametophytes develop through meiosis
when mature, they contain egg cells to fertilize with sperm nuclei
2 years
spring- male cones release pollen grains
carried by wind, stick to sticky secretion on female cones
pollen grain and ovule -> grain splits and grows pollen tube
2 sperm nuclei- one dies, other fertilizes
fertilization -> diploid zygote -> embryo -> seed
sepals
- enclose bud, protect flower
petals
- attract pollinators
stamen
- anther & filament
carpel
- stigma, style, ovary
gametophytes
Full transcript