Lecture_5_-_seed_plants_part_2

Lecture_5_-_seed_plants_part_2 - Calyx Composed of Sepals...

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Calyx Composed of Sepals
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Corolla Composed of petals
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Androecium Androecium Composed of Stamens Composed of Stamens
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Gynoecium Composed of pistils/carpels
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Perfect Flower - Contains both sexes in one flower Complete Flower – contains all 4 whorls Incomplete Flower – lacks one or more of the 4 whorls Both sexes on 1 plant (Two Homes) sexes on separate plants Monoecious (One Home) Dioecious Incomplete Flower Complete Flower
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Many variations in floral structure Have evolved during the 140 million years of angiosperm history
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3 (a) 2 Pollen sac (microsporangium) Micro- sporocyte Micro- spores (4) Each of 4 microspores Generative cell (will form 2 sperm) Male Gametophyte (pollen grain) Nucleus of tube cell 1 75 μ m 20 μ m Ragweed pollen grain MEIOSIS MITOSIS KEY to labels Haploid ( 2n ) Diploid ( 2n ) Anthers contain microsporangia that contain diploid microsporocytes (microspore mother cells). Each microsporo-cyte divides by meiosis to produce 4 haploid microspores, each of which develops into a pollen grain. A pollen grain becomes a mature male gametophyte when its generative nucleus divides & forms 2 sperm. This usually occurs after a pollen grain lands on the stigma of a carpel & the pollen tube begins to grow. The Angiosperm Life Cycle: male gametophyte (pollen grain) development
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Key to labels MITOSIS MEIOSIS Ovule Ovule Integuments Embryo sac Mega- sporangium Mega- sporocyte Integuments Micropyle Surviving megaspore Antipodel Cells (3) Polar Nuclei (2) Egg (1) Synergids (2) Development of a female gametophyte (embryo sac) (b) 1 3 Female gametophyte (embryo sac) Diploid ( 2n ) Haploid ( 2n ) 100 μ m 2 Within the ovule’s megasporangium is a large diploid cell called the megasporocyte (megaspore mother cell). The megasporocyte divides by meiosis & gives rise to 4 haploid cells, but in most species only one of these survives as the megaspore. Three mitotic divisions of the megaspore form the embryo sac, a multicellular female gametophyte. The ovule now consists of the embryo sac along with the surrounding integuments (protective tissue). The Angiosperm Life Cycle: female gametophyte (embryo sac) development The embryo sac contains 8 nuclei: 1 egg, 2 polar nuclei, 3 antipodal cells, 2 synergids
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Stigma Polar nuclei Egg Pollen grain Pollen tube 2 sperm Style Ovary Ovule (containing female gametophyte, or embryo sac) Micropyle Ovule Polar nuclei Egg Two sperm about to be discharged Endosperm nucleus (3 n ) (2 polar nuclei plus sperm) Zygote (2 n ) (egg plus sperm) Double fertilization a unique process to angiosperms After landing on a receptive stigma (pollination) a pollen grain germinates, a pollen tube grows down the style toward the ovary. The pollen tube discharges two sperm into the female gametophyte (embryo sac) within an ovule. One sperm fertilizes the egg, forming the
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This note was uploaded on 05/18/2008 for the course BIOL 211B taught by Professor Lowe/zahn during the Spring '08 term at CSU Long Beach.

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Lecture_5_-_seed_plants_part_2 - Calyx Composed of Sepals...

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