Bio 2.2 Lab Exam 4: Embryology II Frog Development

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Bio 2.2 Lab Exam 4: Embryology II Frog Development
2013-05-07 11:48:14
bio22 labexam4

Frog Development
Show Answers:

  1. What are isolecithal eggs?
    Eggs with very little yolk.
  2. What are mesolecithal eggs?
    Eggs with a medium amount of yolk.
  3. What are telolecithal eggs?
    Eggs with dense heavy yolk.
  4. What is the animal pole of an egg?
    Where the cytoplasm and nucleus can be found at the top of the egg.
  5. What is the vegetal pole of an egg?
    Where the yolk is of an egg at the bottom of the egg.
  6. Where is the pigment layer located in an egg?
    At the top of the egg.
  7. What are the two purposes of the pigment layer?
    • Provides countershading (protection).
    • Absorbs solar radiation to warm the egg.
  8. Where are sperm binding proteins concentrated in an egg?
    The animal hemisphere just above the equator.
  9. What happens right after a sperm cell enters an egg?
    The pigment and cytoplasm move toward the point of sperm entry.
  10. What is the grey crescent?
    A region on the egg that is opposite the sperm entry point.
  11. Where does the first division always begin and end?
    • Begins at the animal pole.
    • Passes through the sperm entrance point and the grey crescent.
    • Proceeds toward the vegetal pole.
  12. Why does the animal pole become the anterior of the animal?
    A concentration of bicoid protein.
  13. Why does the vegetal pole become the posterior of the animal?
    A concentration of nanos.
  14. What does the first cleavage create?
    The right and left sides of the animal.
  15. Are animal hemisphere blastomeres smaller than vegetal blastomeres and why?
    Yes, because vegetal blastomeres have more yolk to cleave.
  16. What stage of cleavage is this in?

    Early Cleavage
  17. Why do the cells of the animal pole divide more quickly than vegetal and what does this create?
    • They are less dense due to the yolk.
    • Blastocoel
  18. What stage in cleavage is this?


  19. How is the blastopore produced?
    • Cells of the animal pole divide rapidly and push against each other.
    • This pushes the vegetal cells to the interior.
    • Eventually they push against each other and curve inward.
  20. What is the process of creating a blastopore called?
  21. What stage in cleavage is this?


  22. What is a notochord?
    A cylinder of connective tissue.
  23. What is the function of the notochord?
    • Adds structure to the embryo.
    • Stimulates organization of other systems by releasing growth factors and stimulating rapid cell division at the surface.
  24. What is the neural groove and what creates it?
    • A band of cells that creates the neural tube.
    • The notochord causes division of the surface cells, causing them to divide and fold inward.
  25. What are the two characteristics of the chordates?
    • Notochord
    • Hollow nerve chord
  26. What are somites?
    They form specific muscles and bones.
  27. What are neural crest cells?
    Form peripheral nerves.