bio mod1 lesson 2-3

• Plant (or the Antennae)


  A green mass in the background of life
• plants

  Begin life as a seed
• Types of seed producing plants


  • Gymnosperms
  • Angiosperms

  
• Gymnosperms


  • Have both male and female parts
  • Group includes conifers, cycads
  • Means 'naked seeds'
• Angiosperms


  • Have flowers and produce seeds enclosed within a carpel
  • Large group including grasses
  • Divided into monocots and dicots
• Monocot seed


  Seed is surrounded with a protective seed coat

  
• Monocot


  • Means 'single leaf'
  • Refers to only seed structure that appears to be homologous
• Monocot cotyledon


  Absorbs digested food from the endosperm
• Scutellum


  A very large cotyledon
• Aleurone layer


  • Lies under the seed coat
  • Functions as a kind of digestive organ in seed germination

  
• Endosperm


  • Food storage tissue
  • Forms separately from the embryo while the seed is attached to the parent

  
• Coleorhiza


  Protects the future root or radicle
• Mesocotyl


  Future stem
• Dicot seed


  • Includes the radicle and plumule
  • Plumule corresponds to the shoot apex in monocots
  • Have two cotyledons
  • Cotyledons function as actual leaves

  
• Embryo and cotyledon development


  1. One fertilization produces the endosperm

  2. The other fertilization produces the zygote which undergoes cleavage

  3. Zygote divisions produce a basal cell and a terminal cell

  
• Suspensor


  Develops from the basal cell into a filament
• Hypocotyl


  Part of the axis below the point of attachment of the cotyledons
• Epicotyl


  • Part above the hypocotyl
  • Embryo in this state of development when the seed becomes dominant

  
• Seed germination


  1. Embryonic plant is kept in a state of suspended development

  2. Ends when germination takes place

  3. Embryo emits the hormone gibberellin which diffuses through the seed
• Zone of division


  • Part of the root tip
  • An apical meristem
• Apical meristem


  Growing tip of embryonic, differentiating tissue
• Zone of elongation


  • Responsible for most of the lengthwise growth of the root tip
  • Growth continues indefinitely
• Zone of maturation


  Tissue differentiation now begins
• Primary meristems


  • Give rise to differentiated tissues such as phloem and xylem
  • Some tissues remain undifferentiated
• Leaf growth


  1. Growing upward as it enlarges and begins to differentiate

  2. Another group of cells next to it begins to grow outward and upward
• Leaf fall


  1. Leaves age and die in all plants

  2. Xylem ages and becomes clogged with resins, turning to heartwood

  3. Cells produced by the cork cambium age and die
• Abscission


  • Process by which plants shed one of their parts
  • Abscission layer is an adaptation that permits loss of leaves and represents a point of weakness
• Secondary growth in dicots


  1. Root and shoot meristems give rise to all plant tissues

  2. Differentiation must occur

  3. Provascular cylinder develops into the vascular tissues

  4. Protoderm becomes the potential epidermis

  5. Ground meristem becomes the cortex and pith
• Monocots usually do not undergo secondary growth
• Primary thickening meristem


  • Immediately behind the apical meristem
  • Great in diameter as the trunk
  • Derived from the apical meristem
  • Continuously enlarges to produce vascular and other differentiated tissues to form the stem
• The diameter of a palm trunk can be somewhat smaller at the base than midway between it and the crown, yet the trunk of a palm seedling is obviously not nearly as great as is that of the mature tree
• Zygote


  A fertilized egg that has the potential to give rise to all the diverse cell types
• Vertebrate zygotes


  • Contain yolk that serves as food for the developing embryo
  • Amount and distribution varies among different animal groups
  • Absent from the human zygote
• Cleavage


  1. Process where the zygote undergoes rapid mitosis

  2. The embryo is pushed along the uterine tube by ciliary action and muscular contraction

  
• Morula


  At about 16 cell stage, the embryo consists of a tiny cluster of cells

  
• Blastocyst


  • Cells arrange themselves into the form of a hollow ball
  • Blastula forms and nutritive membranes surround the embryo
  • Inner cell mass gives rise to the embryo itself
• Implantation


  1. Begins on the seventh day of embryonic development

  2. Enzymes destroy some tiny maternal capillaries in the wall of the uterus

  3. Blood from these capillaries comes in direct contact with the trophoblast
• Formation of germ layers


  1. Cells of the inner cell mass arrange themselves to form a two layer disk

  2. Cells of the lower level then merge to line an inner cavity

  3. Mesoderm proliferates between ectoderm and endoderm
• Ectoderm, mesoderm, endoderm


  The three germ layers
• Photosynthetic reaction


  Combines carbon dioxide with water in two stages to yield glucose and oxygen