Download - Lecture 13, Ch. 30
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Lecture #13 Date ________ Lecture #13 Date ________
Chapter 30 ~Plant Diversity II:
The Evolution of Seed
Plants
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Seed Plant Reproductive AdaptationsSeed Plant Reproductive Adaptations
Reduction of the gametophyte: shift from haploid to diploid condition; female
gametophyte and embryo remain in sporangia (protection against drought and
ionizing radiation on land?)
Advent of the seed multicellular sporophyte embryo with food supply and
protective coat; heterosporous (two types of spores): megaspores--->female
gametophyte--->eggs; microspores---> male gametophyte--->sperm Evolution of pollen: develop from microspores which mature into the male
gametophytes; resistant and airborne for a terrestrial environment; eliminated
water (sporopollenin coats)
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GymnospermsGymnosperms
Cone-bearing plants
Lack enclosed chambers
(ovaries) for seeds
Ovules and seeds develop onspecialized leaves called
sporophylls
Ginkgo, cycads, and conifers
All are evergreens
Needle-shaped leaves Vascular tissue refinement:
tracheids~ water conducting
and supportive element of
xylem
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AngiospermsAngiosperms
Most diverse and geographically widespread of all plants
Flowering plants(Phy:Anthophyta)
Monocots: 1 embryonic seed leaf (lilies, palms, grasses, grain crops)
Dicots: 2 embryonic seed leaves (roses, peas, sunflowers, oaks, maples)
Vascular tissue refinement: vessel elements/fiber cells
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The flower: the defining structure of angiospermsThe flower: the defining structure of angiosperms
Reproductive structure: pollen
transfer; specialized shoot with
modified leaves
Sepals: enclose flower beforeit opens
Petals: attract pollinators
Stamens: male; anther
(produces pollen), filament
Carpels: female; stigma, style,
ovary, ovules
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Seed to flowerSeed to flower Thepeduncle is the tip of the stalk where the
flower begins. The receptacle starts at the peduncle and acts
as a base to which all other parts of the
flower are attached. Sepals are leaf-like protective coverings ofthe bud that grow typically in an outer whorl.Collectively, they are called the calyx.
Petals are the inner whorl of leaves, and areknown collectively as the corolla.
Perianth is the term used when sepals andpetals are grouped together.
Pistils are the female organs. There can beone or more. There are three parts of the
pistil:
thestigma receives the pollen and is
sticky thestyle connects the stigma to the ovary the ovary is where seeds develop
Stamen are the male organs. The number ofstamen per flower varies. There are two partsof the stamen:
the antherproduces pollen the ilamentca s the anther
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Angiosperm lifeAngiosperm life
cyclecycle
Fruit (mature ovary); seeds
from ovules
Pollen grains: 2 haploid cells
(immature male gametophytes)
Ovules (female gametophyte~
embryo sac)
Double fertilization: 1 sperm
w/ egg = diploid zygote; othersperm w/ 2 nuclei in center of
sac = triploid endosperm