Fertilization

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Fertilization Development
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• Fertilization occurs in the oviduct
• Sperm Egg ? Zygote
• Haploid Haploid ? Diploid

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Formation of the Zygote

• Once fertilization has occurred and the genetic
  material has combined, cell division begins.
• Is it mitosis or meiosis?

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Formation of the Zygote

• Once fertilization has occurred and the genetic
  material has combined, cell division begins.
• Is it mitosis or meiosis?
• Mitosis

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Formation of the Zygote

• A special type of mitotic cell division called
• cleavage occurs.

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Formation of the Zygote

• Cleavage results in cells being formed which
  become progressively smaller.

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Formation of the Zygote

• Notice how the over all size remains the same
  while the number of cells increase.

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Formation of the Zygote
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Formation of the Zygote

• Cleavage occurs while the zygote is moving
  through the oviduct.

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Formation of the Zygote

• As the zygote develops it goes through several
  specific phases.
• These are the
• Morula
• Blastula
• Gastrula

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Formation of the Zygote

• The Morula is a solid ball of cells.
• This develops during the first few days after
  conception.

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Formation of the Zygote

• The Blastula is a hollow ball of cells.

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Formation of the Zygote

• The Gastrula is formed from the blastula.
• It establishes the three embryonic tissue
  layers.

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Formation of the Zygote

• The three layers are
• Endoderm
• Mesoderm
• Ectoderm

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Formation of the Zygote

• The ectoderm gives rise to the skin and nervous
  system.

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Formation of the Zygote

• The ectoderm gives rise to the skin and nervous
  system.
• The mesoderm gives rise to the muscles, bones,
  circulatory and excretory systems.

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Formation of the Zygote

• The ectoderm gives rise to the skin and nervous
  system.
• The mesoderm gives rise to the muscles, bones,
  circulatory and excretory systems.
• The Endoderm gives rise to the digestive and
  respiratory systems.

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Implantation

• The Morula secrets a hormone, HcG.
• This maintains
• Progesterone levels, preventing menstruation.

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Implantation

• HcG is detected early and forms the basis for
  the home pregnancy test kits .

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Implantation

• Implantation occurs in the endometrial lining of
  the uterus.
• This occurs by day 7.

21
Associated Structures

• The umbilical cord connects the embryo to the
  placenta.

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Associated Structures

• The umbilical cord connects the embryo to the
  placenta.
• In adults, its scar forms the navel.

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Associated Structures

• The placenta is the site of gas and nutrient
  exchange between the mother and the fetus.

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Associated Structures

• The Amniotic Fluid is the liquid that the baby
  floats in.
• It serves as a cushion.

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Multiple Births

• Multiple births can occur two ways
• The splitting of one fertilized egg that will
  give rise to identical twins

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Multiple Births

• Multiple births can occur two ways
• The splitting of one fertilized egg that will
  give rise to identical twins
• Multiple eggs are fertilized giving rise to
  fraternal twins (not identical)

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Twins
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In Vitro Fertilization

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Types of Sexual Reproduction

• The reproductive pattern shown by mammals and
  marsupials involves internal fertilization and
  internal development.

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Types of Sexual Reproduction

• The reproductive pattern shown by mammals and
  marsupials involves internal fertilization and
  internal development.
• The number of off spring per pregnancy is low
  but parental care is high.

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Types of Sexual Reproduction

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Types of Sexual Reproduction

• The reproductive pattern shown by reptiles and
  birds involves internal fertilization but
  external development (egg)
• The number of off spring is higher, and
  parental care is variable.

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Types of Sexual Reproduction
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Types of Sexual Reproduction

• The reproductive pattern shown by amphibians and
  fish involves external fertilization and external
  development
• The number of off spring is much higher, and
  parental care is usually lacking

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Types of Sexual Reproduction
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Types of Sexual Reproduction

• Regardless of the type of sexual reproduction,
  the development of the embryo is similar.