Plant Reproduction and Plant Diversity II
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Transcript of Plant Reproduction and Plant Diversity II
Plant Reproduction and Plant Diversity II
Chapter 30/38
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• Seed plants - vascular plants that produce seeds.
• 3 adaptations that seed plants have:
• 1Gametophyte more reduced.• 2Seed evolved. • 3Pollen evolved.
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• Gametophytes of seed plants almost invisible.
• Gametophytes still exist - plants can destroy themselves at this stage if there something wrong with plant.
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• Seed - sporophyte embryo packaged with food supply within protective coat.
• Seed plants produce 2 different types of sporangia - produce 2 different types of spores: megaspores (female gametophyte) and microspores.
• Gametophytes stay in sporophyte as it develops.
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• Ovule - integuments (part protective covering), megaspore, and megasporangium.
• Female gametophyte develops inside megaspore; produces 1 + egg cells.
• Fertilized egg develops into sporophyte embryo.
• Whole ovule develops into seed.QuickTime™ and a decompressorare needed to see this picture.
• Microspores (pollen) – light, carried through air.
• Pollen will create pollen tube - allow sperm to travel down into female gametophyte.
• 2 groups of seed plants: gymnosperms and angiosperms.
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Gymnosperms• 4 phyla of gymnosperms still around.• Phylum Ginkgophyta contains only
Ginkgo biloba.
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• Phylum Cycadophyta - cycads - look like palm trees.
• Phylum Gnetophyta - 3 different types of plants (ephedra)
• Phylum Coniferophyta - largest phyla - conifers - from reproductive structure, cone.
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Conifers• Conifers are evergreen - keep leaves
all year long.• Needles help in dry conditions.• Conifers include pines, firs, spruces,
larches, yews, junipers, cedars, cypresses, and redwoods.
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Life cycle of gymnosperms• Conifers - heterosporous (develop
male and female gametophytes)• Produce pollen cones and ovule
cones.• During pollination, pollen falls on
ovule.• Creates pollen tube that digests
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• Megaspore, now fertilized, goes through meiosis to produce 4 haploid cells.
• 1 cell turns into female gametophyte, others (archegonia) will develop within gametophyte.
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Angiosperms• Angiosperms - flowering plants -
produce flowers, fruit.• Phylum Anthophyta - all
angiosperms.• Divided into 2 groups: monocots and
dicots. • Monocots - leaves with parallel veins,
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• Angiosperms - long tracheids - help transport water, support plant.
• Flower specialized for reproduction.• Most angiosperms rely on pollination
through animals; grasses - random chance.
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• Flower - specialized shoot - 4 circles of modified leaves: sepals, petals, stamens, and carpals.
• Sepals - base of flower - modified leaves that enclose flower before it opens.
• Petals lie inside ring of sepals - usually colorful in animal pollinated plants.
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• Male organ - stamen - thin, stalk-like filament with sac at top.
• Anther - produces haploid spores that develop into pollen grains.
• Female organ - pistil - contains 3 parts: stigma, style, ovary.
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• Stigma - sticky top part of flower which extends beyond flower, catches pollen.
• Style connects stigma to ovary at base of pistil which allows sperm to reach ovules.
• Ovary - enlarged area at base of pistil - contains one or more ovules.
• Entire structure - carpal.• Ovule contains egg nucleus.
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• Fruit - mature ovary. • As seeds develop from ovules
after fertilization - wall of ovary thickens to form fruit.
• Fruit helps protect seeds while they disperse.
• Some fruits, dandelion, modified to catch wind.
• Burrs that stick to animals - fruits.
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• Fruit develops after pollination triggers hormonal changes - cause ovarian growth.
• Wall of ovary becomes pericarp (thickened wall of fruit)
• If flower not pollinated - fruit will not develop.
• 3 different types of fruits.QuickTime™ and a decompressorare needed to see this picture.
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• Simple fruits come from single ovary (cherries)
• Aggregate fruit (blackberry) - single flower with several carpals.
• Multiple fruit (pineapple) develops tightly clustered group of flowers.
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• Ovules - contain female gametophyte, embryo sac.
• Angiosperm life cycle starts with mature flower on sporophyte plant and ends with germinating seed.
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• Anthers of flower produce microspores that form male gametophytes (pollen).
• Ovules produce megaspores that form female gametophytes (embryo sacs).
• After its release from anther, pollen carried to sticky stigma of carpal.
• Plants can self-pollinate; cross-pollination better.
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• Pollen grain begins growing from stigma toward ovary.
• Discharges 2 sperm cells into female gametophyte.
• 1 sperm fuses with egg nucleus to form diploid zygote.
• Develops into embryo.• Embryo has rudimentary root;
one (in monocots) or two seed leaves (in dicots), cotyledons.
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• Other sperm nucleus fuses with 2 polar bodies to form endosperm, (triploid or 3n) in monocots.
• Dicots - nutrition goes directly to cotyledons.
• As ovules develop into seeds, ovary develops into fruit.
• Conditions favorable - germination occurs (seed coat ruptures, embryo emerges as seedling) QuickTime™ and a decompressorare needed to see this picture.
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• Seedling uses food stored in either endosperm (monocot) or cotyledon (dicot) to start growth.
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The fruit• Ovary of flower develops into fruit,
protects enclosed seeds, aids in dispersal by wind or animals.
• Wall of ovary becomes pericarp, (thickened wall of fruit)
• Apples - fleshy from swollen receptacles.
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• As seed develops - enters dormancy - allows it to survive until conditions favorable.
• 1st organ to emerge from germinating seed - radicle, embryonic root.
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Asexual reproduction• Plants can clone - vegetative
reproduction.• Fragmentation - parent plant
separates into parts - reform whole plants.
• Scientists use this process to clone plants used for novelty.
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Co-evolution• Certain animals only eat certain
plants - forced evolution of one another.
• Plants evolved special fragrances - forces evolution of specific animals to pollinate these plants.
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Plants and human welfare• All fruit and vegetable crops -
angiosperms.• Corn, rice, wheat, - grass fruits.• Use plants for medicinal
purposes; more than 25% of our prescriptions come from plants.
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