UW BIOL 162 - Angiosperm Reproduction: flowers. (4 pages)

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Angiosperm Reproduction: flowers.



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Angiosperm Reproduction: flowers.

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University of Washington
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Biol 162 - GENERAL BIOLOGY
GENERAL BIOLOGY Documents
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Three differences between gymnosperms and angiosperms Angiosperm Reproduction flowers in reproduction Angiosperm ovules are protected within an enclosed structure rather sitting on a modified leaf Double fertilization in the angiosperms produces a diploid zygote and triploid endosperm nucleus L8 S1 There are generally hermaphrodite flowers and cross pollination between flowers is typical 70 Wind pollination is usual in the gymnosperms Animal pollination widespread in angiosperms Magnolia grandiflora L8 S2 Collective nouns that can cause confusion Basic structure of the angiosperm flower STAMEN male reproductive part CARPEL female reproductive part filament anther stigma style ovary This is a hermaphrodite flower with a single carpel Calyx The outer whorl of a flower made up of sepals that are usually green and protect the flower in bud Carpel Bears the stigma and frequently an elongated style and encloses the ovules sometimes gynaecium The megasporophyll of the flower Corolla The collective term for the petals of a flower OVULE forms within ovary petal all petals combined are the flower s corolla sepal all sepals combined are the flower s calyx Fig 28 2 p 495 receptacle L8 S3 L8 S4 More collective nouns that can cause confusion Ovary An ovary is a female reproductive organ in plants that produces ovules Ovule The female sex cells of flowering plants After the ovule is fertilized by the male pollen the ovule becomes a seed Pistil The central set of female reproductive organs The pistil is composed of one or more carpels and produces the ovule Perianth The floral envelope it includes the calyx and corolla Stamen The anther and its supporting filament The microsporophyll of the flower Plant of the day L8 S5 1 Wreaths of Damask like roses have been found in Egyptian tombs Minoan frescoes on Crete show roses and gold pins with single rose flower on the end were discovered at Knososs Nebuchadnezzar used roses to decorate his palace The Greeks associated roses with the blood of Aphrodite s beloved Adonis 0 my love is like a red red rose that s newly sprung in June 0 my love is like a melody that s sweetly play d in tune As fair thou art my bonnie lass so deep in love am I And I will love thee still my dear till a the seas gang dry Robert Burns 1759 1796 The annual U S consumption of roses is 4 7 flowers per person The rose is the national flower of the U S since 1987 The rose is the national flower of England since 1485 Angiosperm ovules are protected within an enclosed structure rather sitting on a modified leaf as in the gymnosperms Evolution of the pistil L8 S6 Remember angeion case this is how we think it evolved Have you ever eaten anything like this Life cycle of Angiosperms Your book Fig 28 5 p 496 Overview of cherry life cycle Flower The basic life cycle appears Ovule formation similar to that of the Gymnosperms seed fertilization mature sporophyte DIPLOID HAPLOID meiosis within anther meiosis within ovary gametes sperm microspores mitosis male gametes gametophyte megaspores eggs mitosis female gametophyte Seedling BUT there is a well developed receiving system for the pollen so that the male gametophyte can penetrate the angion the female gametophyte has a more complex structure that results in an endosperm nutritive material for the embryo L8 S7 Seed Meiosis Double Fertilization Diploid Stage Meiosis Haploid Stage Pollen development Pollination Development of embryo sac L8 S8 2 pollen sac see next slide Anther cutaway view filamen t one of the microspore mother cells inside a pollen sac Diploid Stage Meiosis Haploid Stage Ways in which Angiosperms are different from Gymnosperms How pollen grains develop and germinate Double fertilization in the angiosperms produces a diploid zygote and triploid endosperm Meiosis I and II each followed by cytoplasmic division results in four haploid n microspores Mitosis in a microspore gives a 2 celled haploid pollen grain One cell will grow to be the pollen tube The other will produce two sperm nuclei pollen tube Pollen release see next slide sperm nuclei stigma mature male gametophyte style of carpel L8 S9 L8 S10 The fertilization process in Angiosperms Somatic cell division involves two successive steps mitosis and cytokinesis an ovule Now remind me what is cytokinesis again seed In mitosis the nuclear DNA duplicates and chromosomes segregates equally between the two daughter nuclei cytokinesis divides these two nuclei and cytoplasm including related cytoplasmic organelles into two individual cells ovary wall seedling 2n seed coat embryo 2n endosperm 3n Meiosis Haploid Stage pollen tube embryo sac inside ovule endosperm mother cell n n L8 S11 L8 S12 ovary cutaway view Diploid Stage Double Fertilization cell integument stalk 3 megaspores disintigrate integuments egg n One sperm nucleus to the Cytoplasmic division then gives 7 cells egg one to the endosperm mother cell the endosperm mother cell with 2 nuclei Meiosis I and II each followed by cytoplasmic division result in 4 haploid megaspores Three rounds of mitosis with NO CYTOPLASMIC DIVISION produces a megaspore with 8 haploid nuclei Variety in animal pollination The vine Mucuna holtonii with a small concave mirror that reflects a bat s echolocation and guides the animal to its nectar Marc Holderied University of Erlangen Germany Shortcut to Movie flowering lnk Erythrina crista galli crybabytree The anthers are positioned to dust the top of the hummingbird as it drinks L8 S13 Arisaema triphyllum Jack in the pulpit The actual flowers are tiny and located on the cylindrical spadix inside the spathe L8 S14 3 Yucca Yucca filamentosa Adam s needle Each species of yucca is apparently pollinated by a single highly specialized species of moth The moth has special appendages that it uses to actively pack pollen onto the stigma It then oviposits its eggs directly into the ovary The developing larvae eat part of the developing seeds but this cost is outweighed by the benefit of having an efficient and reliable pollinator If a moth oviposits too many eggs on a flower the flower will abort and drop off the plant selecting against individuals that overexploit the plant The yucca yucca moth system is one of the clearest examples of coevolution between plants and animals A female yucca moth Tegeticula maculata in the upright pollination position on the pistil of Yucca whipplei She forces pollen down into the central stigmatic depression thus pollinating the flower L8 S15 Pollen and stigma


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