Plant Reproduction and Plant Diversity II

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Plant Reproduction and Plant Diversity II

• Chapter 30/38

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• Seed plants - vascular plants that produce seeds.
• 3 adaptations that seed plants have
• 1Gametophyte more reduced.
• 2Seed evolved.
• 3Pollen evolved.

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• Gametophytes of seed plants almost invisible.
• Gametophytes still exist - plants can destroy
  themselves at this stage if there something wrong
  with plant.

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http//www.palaeos.com/Plants/Images/Physcomitrell
aRhizoids.jpg
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• Seed - sporophyte embryo packaged with food
  supply within protective coat.
• Seed plants produce 2 different types of
  sporangia - produce 2 different types of spores
  megaspores (female gametophyte) and microspores.
• Gametophytes stay in sporophyte as it develops.

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http//botit.botany.wisc.edu/images/130/Early_deve
lopment/Bean/bean_seed_2_MC.low.jpg
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• Ovule - integuments (part protective covering),
  megaspore, and megasporangium.
• Female gametophyte develops inside megaspore
  produces 1 egg cells.
• Fertilized egg develops into sporophyte embryo.
• Whole ovule develops into seed.

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• Microspores (pollen) light, carried through
  air.
• Pollen will create pollen tube - allow sperm to
  travel down into female gametophyte.
• 2 groups of seed plants gymnosperms and
  angiosperms.

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http//www.hepafilters.com/images/pollen.gif
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Gymnosperms

• 4 phyla of gymnosperms still around.
• Phylum Ginkgophyta contains only Ginkgo biloba.

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• Phylum Cycadophyta - cycads - look like palm
  trees.
• Phylum Gnetophyta - 3 different types of plants
  (ephedra)
• Phylum Coniferophyta - largest phyla - conifers -
  from reproductive structure, cone.

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Conifers

• Conifers are evergreen - keep leaves all year
  long.
• Needles help in dry conditions.
• Conifers include pines, firs, spruces, larches,
  yews, junipers, cedars, cypresses, and redwoods.

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http//www.cambridge2000.com/gallery/images/P30751
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Life cycle of gymnosperms

• Conifers - heterosporous (develop male and female
  gametophytes)
• Produce pollen cones and ovule cones.
• During pollination, pollen falls on ovule.
• Creates pollen tube that digests through
  megaspore.

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http//cache.eb.com/eb/image?id62941rendTypeId4
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• Megaspore, now fertilized, goes through meiosis
  to produce 4 haploid cells.
• 1 cell turns into female gametophyte, others
  (archegonia) will develop within gametophyte.

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Angiosperms

• Angiosperms - flowering plants - produce flowers,
  fruit.
• Phylum Anthophyta - all angiosperms.
• Divided into 2 groups monocots and dicots.
• Monocots - leaves with parallel veins, dicots
  have netlike venation.

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• Angiosperms - long tracheids - help transport
  water, support plant.
• Flower specialized for reproduction.
• Most angiosperms rely on pollination through
  animals grasses - random chance.

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• Flower - specialized shoot - 4 circles of
  modified leaves sepals, petals, stamens, and
  carpals.
• Sepals - base of flower - modified leaves that
  enclose flower before it opens.
• Petals lie inside ring of sepals - usually
  colorful in animal pollinated plants.

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• Male organ - stamen - thin, stalk-like filament
  with sac at top.
• Anther - produces haploid spores that develop
  into pollen grains.
• Female organ - pistil - contains 3 parts stigma,
  style, ovary.

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http//img.sparknotes.com/figures/B/b1ab5bb87aee74
a86fdae78ed564e663/flower.gif
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• Stigma - sticky top part of flower which extends
  beyond flower, catches pollen.
• Style connects stigma to ovary at base of pistil
  which allows sperm to reach ovules.
• Ovary - enlarged area at base of pistil -
  contains one or more ovules.
• Entire structure - carpal.
• Ovule contains egg nucleus.

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http//park.org/Taiwan/Culture/Arts/flowers/religi
ous/LB210302g2.jpg
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• Fruit - mature ovary.
• As seeds develop from ovules after fertilization
  - wall of ovary thickens to form fruit.
• Fruit helps protect seeds while they disperse.
• Some fruits, dandelion, modified to catch wind.
• Burrs that stick to animals - fruits.

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• Fruit develops after pollination triggers
  hormonal changes - cause ovarian growth.
• Wall of ovary becomes pericarp (thickened wall of
  fruit)
• If flower not pollinated - fruit will not
  develop.
• 3 different types of fruits.

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http//www.simplyclassicfruitbaskets.com/pic/fruit
_festival_home.jpg
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• Simple fruits come from single ovary (cherries)
• Aggregate fruit (blackberry) - single flower with
  several carpals.
• Multiple fruit (pineapple) develops tightly
  clustered group of flowers.

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• Ovules - contain female gametophyte, embryo sac.
• Angiosperm life cycle starts with mature flower
  on sporophyte plant and ends with germinating
  seed.

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http//www.lclark.edu/seavey/bio210/flower_dwg_ov
ules_pjt.gif
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• Anthers of flower produce microspores that form
  male gametophytes (pollen).
• Ovules produce megaspores that form female
  gametophytes (embryo sacs).
• After its release from anther, pollen carried to
  sticky stigma of carpal.
• Plants can self-pollinate cross-pollination
  better.

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http//utc.usu.edu/factsheets/CarexFSF/CIG/rhexia_
anthers4_lg.jpg
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• Pollen grain begins growing from stigma toward
  ovary.
• Discharges 2 sperm cells into female gametophyte.
• 1 sperm fuses with egg nucleus to form diploid
  zygote.
• Develops into embryo.
• Embryo has rudimentary root one (in monocots) or
  two seed leaves (in dicots), cotyledons.

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http//biofinity.org/images/Pollen20Grain20Micro
graph.jpg
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• Other sperm nucleus fuses with 2 polar bodies to
  form endosperm, (triploid or 3n) in monocots.
• Dicots - nutrition goes directly to cotyledons.
• As ovules develop into seeds, ovary develops into
  fruit.
• Conditions favorable - germination occurs (seed
  coat ruptures, embryo emerges as seedling)

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http//www.rbgsyd.nsw.gov.au/__data/assets/image/0
017/81026/Seed_germination_620.JPG
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http//www.wheatbp.net/Dissex-A.jpg
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• Seedling uses food stored in either endosperm
  (monocot) or cotyledon (dicot) to start growth.

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The fruit

• Ovary of flower develops into fruit, protects
  enclosed seeds, aids in dispersal by wind or
  animals.
• Wall of ovary becomes pericarp, (thickened wall
  of fruit)
• Apples - fleshy from swollen receptacles.

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• As seed develops - enters dormancy - allows it to
  survive until conditions favorable.
• 1st organ to emerge from germinating seed -
  radicle, embryonic root.

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Asexual reproduction

• Plants can clone - vegetative reproduction.
• Fragmentation - parent plant separates into parts
  - reform whole plants.
• Scientists use this process to clone plants used
  for novelty.

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Co-evolution

• Certain animals only eat certain plants - forced
  evolution of one another.
• Plants evolved special fragrances - forces
  evolution of specific animals to pollinate these
  plants.

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Plants and human welfare

• All fruit and vegetable crops - angiosperms.
• Corn, rice, wheat, - grass fruits.
• Use plants for medicinal purposes more than 25
  of our prescriptions come from plants.

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