Sexxxxuality in Angiosperms

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Sexxxxuality in Angiosperms

• Extreme reduction of the gametophyte
• Complete independence of water
• for fertilization
• Stored food in seed to nourish embryo
• Fruit protect offspring seeds inside
• Fruits help disperse seeds into the world
• Co evolution of insects and plants

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Figure 38.3a Trillium dioecious flower (
bisexual)
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idealized flower
male
female
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Figure 38.3ax1 Lily
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N pollen grains ( male gametophyte )
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Pollen grains thick, patterned outside walls
identify species of plants
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A Pollen grain is a male gametophyte Pollen
grains are N What is inside a pollen grain?
A pollen grain is a thick container Inside
there is a cell within a cell. An outer tube
cell contains a sperm cell
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Mature pollen grains
Generative cell is inside the tube cell, inside
the pollen grain
N
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Pollination occurs when pollen lands on the
stigma Cross pollination involves pollen from
another flower Self pollination involves pollen
from the same flower Flowers usually opt first
to cross pollinate before
self pollinating Some can only cross
pollinate Fertilization 2 sperm nuclei enter
the embryo sac one
fertilizes egg , one helps
form 3N endosperm View video clip on
pollination http//www.emunix.emich.edu/ghannan/s
ystbot/doublefertanimation.html
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Ovule formation inside ovary Female ovules
inside the ovary Each ovule is the female
gametophyte
ovary
ovules
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• Each embryo sac/ovule ( female gametophyte )
• will become a seed when fertilized
• The ovule has
• an egg cell which is N
• 2 polar nuclei which are each N
• and 5 other cells which eventually degenerate

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Sporophyte flower
Embryo sac (gametophyte)
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each is N
form from generative nucleus
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Stored food for seed
Double fertilization, a key term
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Figure 38.1 Simplified overview of angiosperm
life cycle
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Figure 38.3d1 Pollination modesco evolution
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Figure 38.3e Maize, a monoecious species
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Figure 38.11 Seed structure
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Figure 38.12 Development of a pea fruit (pod)
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Figure 38.13 Mobilization of nutrients during
the germination of a barley seed
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Root cross section and transport
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