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A New Generation Begins AP Biology Spring 2011 Pollen Formation: • In _______, large numbers of diploid “__________ mother” cells divide by meiosis to form four ___________ microspores • Each microspore will divide by _________ and differentiate to form _________ __________ • Each pollen grain consists of an inner cell located in the cytoplasm of the outer cell; both cells are surrounded by a ______________ ______ Egg Formation: • In the _______, a mass of tissue form ovules (potential seeds) enclosed by integuments (protective tissue) • A ________ “megaspore mother” cell divides by meiosis to produce ______ _________ megaspores, three of which ________________ Egg Formation: • The surviving _______ undergoes three rounds of mitosis with no _________ division generating a single cell with eight haploid nuclei • Ultimately the cytoplasm divides _________ to produce seven cells; one ________ egg cell, one __________ mother cell with two haploid nuclei, and five cells that support the process of ___________________ When a pollen grain lands on a ________, pollination has occurred After a pollen grain lands on a stigma, one of the two pollen cells forms a ______ _____; the other cell divides by mitosis to produce ____ sperm cells Guided by chemical cues, the pollen tube grows through the tissues of the ______ to an ovule When the _________ _______penetrates the embryo sac, the two sperm cells travel down the pollen tube and complete the ________ fertilization event • One sperm fuses with the egg nucleus to form a diploid zygote • The other sperm nucleus fuses with the two endosperm nuclei in the endosperm mother cell to yield a triploid endosperm, which will nourish the young developing plant http://www.youtube.com/watch?v=Gq8N Wh98wQs