Angiosperm Reproduction

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Angiosperm Reproduction
AP Biology Unit 5
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Flower Anatomy

• The flower is the reproductive organ of an
  angiosperm
• Female part Carpel
• Consists of the stigma, style, and ovary
• Male part Stamen
• Consists of anther and filament

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Angiosperms

• Dominant form is the sporophyte
• Heterosporous
• Male gametophyte pollen grain
• Female gametophyte embryo sac

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Female Gametophyte

• The megaspore will go through MITOSIS to create a
  series of different cells in the female
  gametophyte
• Cells involved in fertilization are
• Egg (n) haploid
• Polar nuclei (2n) 2 nuclei in one cell

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Double Fertilization

• Angiosperm fertilization actually consists of 2
  separate fertilization events double
  fertilization
• Both sperm in the pollen tube are used
• One sperm fertilizes the egg ? diploid zygote
  (2n) forms
• The other sperm fertilizes the polar nuclei (2n)
  ? forms triploid endosperm (3n)

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Double Fertilization

• Double fertilization is unique to angiosperms
• Through this process, resources are used most
  efficiently since endosperm can only develop in a
  fertilized ovule.
• Endosperm starchy material that serves as
  nutrition for the growing embryo

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Other Post-Fertilization events

• Embryo develops
• Seed coat forms
• Ovary develops into fruit around the seed

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Germination and Seedling Formation

• Seeds are dormant until they begin germination
• When conditions are right, seeds will begin to
  germinate to form a seedling.
• Germination starts with imbibitionwhen water
  enters the seed and triggers enzymes that are
  needed for growth.

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Seed Benefits

• What are the evolutionary benefits of seeds?
• Dispersal- embryo can travel far from parent
• Protection- seed coat protects embryo
• Dormancy- can wait until conditions are favorable
  to germinate
• Storage- food for the embryo can be stored inside
  seed (ex. endosperm)

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Monocots vs. Eudicots

• Most angiosperms can be classified as either
  Monocots or Eudicots

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