Biology Lesson 2

• Gametophyte


  Stage of the life cycle of a plant that is haploid; stage that produces gametes via mitosis; these gametes fuse to form a zygote that develops into a sporophyte

  
• Sporophyte


  Stage of the life cycle of a plant that is diploid; it is the most recognizable structure in most flowering plants; it produces haploid spores by meiosis in structures called sporangia

  
• Life cycle where the haploid stage (gametophyte) is multicellular and the only diploid stage is the fertilized egg cell


  1. Mature, multicellular organism is a diploid sporophyte

  2. Cells undergo meiosis to produce haploid gametes which fuse to form zygote

  3. Zygote develops by mitosis to become multicellular diploid sporophyte

  
• Life cycle that includes multicellular diploid (sporophyte) and haploid (gametophyte) generations


  1. Dominant part of life cycle is a multicellular, haploid gametophyte

  2. Mitosis releases individual cells that can act like gametes

  
• Life cycle where the diploid stage (sporophyte)is multicellular and the haploid stage (gametophyte) is represented by the single-celled gametes


  Organism is in the diploid stage except for mature, haploid sex cells which are called gametes

  
• Four major whorls of a flower

  • Sepals
  • Petals
  • Stamen
  • Pistil or carpels
• Stamen


  The male reproductive structure of the flower; bears the male sporangia (also known as microsporangia)
• Anther


  Part of the stamen that contains the microsporangia that develops into pollen grains
• Filament


  Part of the stamen that serves as the stalk of the anther
• Pistil or carpels


  The female reproductive structure of the flower; bears the female sporangia (also known as the megasporangia)
• Stigma


  Part of the pistil where the pollen grain derived from the microsporangium attaches during pollination
• Style


  Part of the pistil that serves as the stalk of the stigma; leads to the ovary
• Ovary


  Found at the base of the pistil; contains one or more ovules; eventually becomes the fruit
• Ovule


  Contains the female sporangia or megasporangia; eventually becomes the seed
• Types of flowers


  • Complete
  • Incomplete
• Types of flowers based on sex organs

  • Perfect / Bisexual
  • Imperfect / Unisexual
• Types of plants based on sex organs

  • Monoecious
  • Dioecious
• Male gametophyte development


  1. Microsporangium in anther contains microsporocytes

  2. Microsporocytes undergo meiosis to produce microspores

  3. Microspores develop into pollen grains

  
• Female gametophyte development


  1. Megasporangium in ovule contains megasporocytes

  2. One megasporocyte undergoes meiosis to produce megaspores

  3. Remaining megaspore divides mitotically to form embryo sac

  
• Pollination


  Placement of pollen grain from anther to stigma of carpel
• Pollen grain


  Immature male gametophyte that develops within anthers; derived from microsporocytes

  
• Fertilization


  1. Pollen tube elongates along style and penetrates ovule

  2. One sperm fuses with egg to form zygote

  3. Other sperm fuses with polar nuclei to form endosperm
• Embryo sac


  Female gametophyte found inside ovule; derived from megasporocyte; contains egg cell, synergids, polar cells, and antipodals

  
• Embryo development


  1. Zygote divides mitotically to produce proembryo and suspensor

  2. Proembryo elongates into embryo with cotyledons
• Endosperm


  Nutritive tissue derived from fusion of sperm nucleus and polar nuclei; stores food for developing embryo
• Zygote

  Part of mature seed that forms from fusion of egg and sperm
• Cotyledon


  Embryonic leaf that forms inside seed
• Types of cotyledons


  • Monocot (one cotyledon)
  • Dicot (two cotyledons)
• Seed germination


  1. Imbibition (water absorption)

  2. Radicle (embryonic root) emerges

  3. Plumule (embryonic shoot) breaks through soil
• Micropyle


  Opening in ovule integuments where pollen tube enters to reach embryo sac
• Epicotyl


  Part of plumule above cotyledon
• Hypocotyl


  Part of plumule below cotyledon
• Transformation of seed to seedling

  1. Imbibition breaks dormancy

  2. Nutrients from endosperm/cotyledons transferred to growing regions

  3. Primary meristems develop to form radicle and plumule
• Types of seed germination

  • Epigeal (cotyledon emerges above ground)
  • Hypogeal (cotyledon remains below ground)
• Fruit and seed development

  1. Ovary matures into fruit, ovule becomes seed

  2. Seed may become dormant
• Plant tissue differentiation


  Primary meristems differentiate into different plant tissues