UNIT 3_notes - UNIT 3: Angiosperm Life Cycle: most diverse...

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UNIT 3: Angiosperm Life Cycle: - most diverse group of plant - key features distinguish angiosperms from ferns - flower anatomy - microsporogenesis and microgametogenesis development of pollen grain _____________________________ Angiosperms= flowering plants - 250,000 species - arose 150 million years ago - 2 unique features o 1) Flower: pollination (efficient and precise control over reproduction) increase in efficiency of sexual reproduction allows for greater degree of outcrossing o 2) Fruit: protection of seed dispersal of seed 1) All angiosperms are heterosporous while most ferns are homosporous a. Which means that angiosperm sporophytes develop 2 types of spores i. Microspores microgametophyte (produces SPERM) ii. Megaspores structure called the megagametophytes (produces the EGG) 2) Reduction in SIZE of gametophyte generation a. Ferns have 100s of cells in the gametophyte generation b. In angiosperms microgametophytes have 3 CELLS
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megagametophytes have 7 CELLS 3) Gametophytes are COMPLETELY DEPENDENT on PARENTAL SPOROPHYTES a. Spores that are never released divide into gametophytes within sporophytes 4) Increased specialization of reproductive structures a. In ANGIOSPERMS: SEEDS, FLOWERS, and FRUIT b. Provide PROTECTION, CONTROL over fertilization, and NUTRITION and DISPERSAL of offspring 5) Unit of dispersal SEED a. Provides protection and nutrients for the young embryo 6) Non-motile sperm delivered to egg by pollen a. Wide range of habitats The FLOWER is produced by the SPOROPHYTE GENERATION of plants - Flower = the site of sexual reproduction - The STAMEN (located in the anthers) is where MICROSPORES ARE PRODUCED o Microspores develop into microgametophytes o We call microgametophytes POLLEN (aka, the SPERM of the plant)
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- Within the ovule, the megaspores form, then develop into megagametophytes which then produce the eggs - The OVARY matures into the FRUIT - Floral organs = modified leaves (plants only have 3 organs: leaves, roots, and stems) The 2 most advanced angiosperm families: 1) orchids= verspecialized, highly modified flowers 2) aster family composites a. ex: Sunflowers b. a group of spall flowers put together i. one daisy has about 20 more flowers than a rose does Anther Cross Section:
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Microsporangium = the site of 2 processes 1) Microsporogenesis formation of microspores 2) Microgametogenesis formation of microgametophytes Angiosperm Development: - microsporagenesis and microgametogenesis - pollen grain = 3 cells (one tube cell and two sperm cells) - megasporogenesis and megagametogenesis o embryo sac = 7 cells o monosporic vs. tetrasporic ____________________ - In roughly 33% of species, division occurs within the anther
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- In roughly 67% of species, division occurs only after pollen is released and it lands on a stigma The Pollen Grain: - Thin spots in the wall that are pores or furrows that allow the pollen tube to exit - Lots of stored nutrients (lipids, carbohydrates, and proteins) in the
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This note was uploaded on 04/18/2010 for the course BIOLOGY 1308 taught by Professor Larryruben during the Spring '10 term at Southern Methodist.

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UNIT 3_notes - UNIT 3: Angiosperm Life Cycle: most diverse...

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