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					Plant Reproduction
   Thinking Question:


• Is a seed alive? Is a fruit alive? Answer
  as completely as you can on your own
  paper. (Hang on to your paper until the
  end of class.)
Asexual Reproduction

• Asexual reproduction is natural “cloning.”
  Parts of the plant, such as leaves or
  stems, produce roots and become an
  independent plant.
• List some benefits and some drawbacks
  to asexual reproduction.
 Sexual Reproduction

• Sexual reproduction requires fusion of
  male cells in the pollen grain with female
  cells in the ovule.
• List some advantages and drawbacks to
  sexual reproduction.
      Terms to know:
• Haploid: having a single set of
  chromosomes in each cell.
• Diploid: having two sets of chromosomes
  in each cell.
• Mitosis: cell division, which produces two
  genetically identical cells.
• Meiosis: reduction division, which
  produces four haploid reproductive cells.
Plant Life Cycle
       Animals vs. Plants
               Plant Reproduction Animal Reproduction

                   Alternation of        No alternation of
  Life cycle
                   generations             generations

  Gametes        Haploid gametes         Haploid gametes

   Spores         Haploid spores            No spores

Gametes made Haploid gametophyte,       Diploid organism, by
     by           by mitosis                   meiosis

Spores made    Diploid sporophyte, by
                                            No spores
     by                meiosis
Alternation of Generations

 • Plants have a double life cycle with two
   distinct forms:
  • Sporophyte: diploid, produce haploid
    spores by meiosis.
  • Gametophyte: haploid, produce
    gametes by mitosis.
 Non-flowering plants

• Mosses, ferns, and related plants have
  motile, swimming sperm.
• What kind of environmental conditions
  would be required for reproduction in
  these plants?
• What kinds of limits does external
  reproduction impose on these plants?
Moss Life Cycle
Fern Life Cycle
             Conifers

• Conifers (also non-flowering plants) have
  reduced gametophytes.
 • Male gametophyte is contained in a dry
   pollen grain.
 • Female gametophyte is a few cells
   inside of the structures that become
   the seed.
Conifer life cycle
    Conifer pollination
• Conifers are wind-pollinated plants.
• Chance allows some pollen to land on
  the scales of female cones.
• Pollen germinates, grows a pollen tube
  into the egg to allow sperm to fertilize the
  egg.
• What are some advantages and
  disadvantages to wind pollination?
  Pollen go-betweens
• Showy flowers are the result of selection
  for more efficient pollination strategies.
• Flower parts are modified leaves. Those
  that were brightly colored attracted
  insects in search of pollen.
• Why would insects search for pollen?
  What other rewards do flowers offer?
• What are advantages and disadvantages
  to relying on insects as pollinators?
Flowers
Flower Parts
   Incomplete flowers
• Flowers are complete if they have all
  parts, and perfect if they have both male
  and female parts.
• Grass flowers: incomplete, usually
  imperfect (separate male and female
  flowers)
• A tulip is complete (though the sepals
  are the same color as the petals) and
  perfect.
Imperfect flowers
Gametogenesis: Male
Gametogenesis: Female
  Double
Fertilization
Angiosperm Life Cycle
    Thinking question


• Use what you have learned about plant
  life cycles to explain why most mosses
  and ferns live in moist environments, but
  flowering plants can live just about
  anywhere.

				
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