Bio Chapter 25

Bio Chapter 25 - Chapter 25: Plant Reproduction and...

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Chapter 25: Plant Reproduction and Development
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Asexual Reproduction Part of a single plant divides by mitosis to give rise to a new plant Spreading of runners (strawberries) Production of bulbs( daffodils) Sprouting of rhizomes (irises) Offspring are genetically identical to parent plant Advantageous in a stable environment
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Sexual Reproduction Two parent plants give rise to genetically variable offspring Involves meiosis, gamete formation, and fertilization Allows offspring to cope with a changing environment or invade different habitats
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Plant Life Cycle Is Characterized by Alternation of Generations Multicellular diploid plants ( sporophytes ) and multicellular haploid plants ( gametophytes ) take turns producing each other
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Alternation of Generations (AOG) In seedless plants (mosses and ferns): Gametophytes are independent plants Mobile sperm swim through water to egg Reproduction restricted to moist habitats In seed plants (gymnosperms and angiosperms): Gametophytes develop within sporophytes Sperm contained within tough, watertight pollen grains dispersed by wind or pollinators Reproduction can occur in dry habitats
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AOG in Flowering Plants Diploid sporophyte produces flowers Within each flower, 2 types of haploid spores Megaspore divides by mitosis to form female gametophyte ( embryo sac ), retained in flower Microspore divides by mitosis to form male gametophyte ( pollen grain ) Sperm released from pollen grain when it lands on female structure of another plant Sperm burrow to egg and fuse to form a diploid zygote, becomes encased in a seed Seed germinates to form a new sporophyte
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Non-Flowering Gymnosperms Were the Earliest Seed Plants Gymnosperms bear male and female gametophytes on separate cones Male cones release pollen grains that travel via wind to female cones Wind pollination is inefficient because most pollen grains fail to reach their target
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Flowering Plants Evolved from Gymnosperms Angiosperms bear male and female gametophytes on flowers Flowers produce pollen and nectar that attract animal pollinators (bees, moths, butterflies, hummingbirds) Flowers enhance a plant’s reproductive success because animal pollinators transport pollen from plant to plant as they feed
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Sepals - located at base of flower; surround and protect the bud
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Bio Chapter 25 - Chapter 25: Plant Reproduction and...

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