Biology 172 FINAL EXAM: Animal Development

  1. 1) very little yolk present in egg
    2) yolk is uniformly distributed in egg
    3) examples: sea urchins and placental mammals
    isolecithal eggs
  2. 1) some yolk is present
    2) yolk tends to be more concentrated near the vegetal pole
    3) early cleavages are complete (holoblastic; see below)
    4) examples: amphibians
    telolecithal-holoblastic eggs
  3. 1) much yolk is present
    2) cytoplasm of egg largely excluded from yolk
    3) cytoplasm sits as a disc on the animal side of the egg
    4) early cleavages incompletely divide the egg cytoplasm (meroblastic; see below)
    5) examples: reptiles and birds
  4. small-to-moderate amount of yolk allows complete division of the blastomeres
    holoblastic cleavage
  5. large yolk results in incomplete cleavages, thus many blastomeres may be connected via cytoplasmic bridges for a time
    meroblastic cleavage
  6. 1) isolecithal eggs exhibit holoblastic cleavage
    2) early solid ball of blastomeres = morula
    3) classic blastula stage is final result of cleavage
    sea urchins
  7. 1) telolecithal egg with moderate yolks exhibits holoblastic cleavage
    2) after fertilization pigmented egg cortex slides over exposing grey crescent and establishing major body axes (Fig. 47.21, p. 1037)
    3) blastomeres on vegetal side larger than those on animal side
    4) blastocoel partly filled with yolky cells on the vegetal side
  8. 1) telolecithal egg with large amount of yolk exhibits meroblastic cleavage
    2) at end of cleavage, blastula stage represented by a flat disc of cells (the blastoderm) overlying the yolk
    a) two layers: epiblast and hypoblast
    b) blastocoel lies between these two layers
  9. 1) isolecithal egg exhibits holoblastic cleavage
    2) early cleavage stages yield morula
    3) final result of cleavage: blastocyst 
    a) inner cell mass will become the embryo
    b) trophoblast will contribute to the placenta
    4) implantation
  10. consequences
    a. formation of the embryonic gut (= archenteron)
    b. also establishes the three primary germ layers: endoderm, ectoderm, mesoderm
  11. a) outermost living layer (i.e., the epidermis) of the body coverings 
    b) epidermal structures such as reptilian scales, avian feathers, hair, toe & finger nails
    c) brain, dorsal hollow nerve cord, optic cup, and other nerve elements
  12. a) notochord
    b) body musculature
    c) main skeletal elements
    d) circulatory, reproductive, & excretory systems
    e) lining of the coelomic cavities
  13. a) innermost lining of the gut tube
    b) plus the derivatives of this tube
    1) lungs
    2) liver
    3) pancreas
    4) bladder
  14. 1) involves invagination from the vegetal pole
    2) mesenchyme cells form filopodia that help drag the archenteron inward
    3) blastopore represents the anus
    sea urchin gastrulation
  15. 1) presumptive endoderm cells roll inward (involution) forming the blastopore lip
    2) eventually original blastocoel shrinks away as archenteron forms
    3) blastopore region filled with yolk cells: the yolk plug
    amphibian gastrulation
  16. 1) presence of yolk interferes with typical pattern of gastrulation
    2) epiblast cells migrate medially and coverge
    3) cells in convergence zone (primitive streak) sink to form underlying endoderm and mesoderm in between
    4) three-layered flat embryo sits on top of the yolk
    bird gastrulation
  17. 1) embryo prior to gastrulation is a flat disk with two cell layers (epiblast and hypoblast) as occurs in reptiles in birds
    2) yolk sac beneath embryo does not contain yolk
    3) gastrulation basically is like what is observed in birds and reptiles
    human gastrulation
  18. 1) implantation
    2) gastrulation
    3) extraembryonic membranes form
    4) organogenesis
    5) embryo becomes a fetus at eight weeks
    first trimester
  19. 1) most body organs formed, but mature throughout this phase
    2) mainly fetal growth
    3) placenta produces progesterone
    second trimester
  20. 1) continued fetal growth
    2) continued maturation of body organs
    3) ends in labor and parturition
    4) hormones involved with human labor
    third trimester
  21. high ______ near the end of pregnancy stimulate oxytocin receptors of uterine muscles
  22. fetal pituitary gland secretes ______ stimulating uterine contraction
  23. discomfort and stress from uterine contractions stimulates maternal ______ secretion leading to more intense and frequent contractions (positive feedback loop)
  24. _______ also brings the uterus back to normal size following childbirth (this _______ production is stimulated by breast feeding)
  25. 1) softens the fibrocartilage uniting the pubic bones
    2) softens the cervix, allowing it to dilate
    relaxin (produced by the ovary and placenta)
  26. a. expands and envelopes embryo as archenteron forms by a folding of the embryo from a disk to a tube
    b. formed of ectoderm and mesoderm
    c. encloses the embryo into a fluid-filled cavity
  27. a. formed from the original trophblast and mesoderm
    b. fuses with the allantois to provide gas exchange in reptiles and birds
    c. chorioallantoic membrane in mammals contributes to the placenta
  28. a. formed of endoderm and mesoderm as an outpocketing of the archenteron
    b. stores metabolic wastes
    c. contributes to chorioallantoic membrane
  29. a. formed from endoderm and mesoderm
    b. connected to the archenteron via the yolk stalk
    c. contains the yolk in reptiles
    d. no yolk in yolk sac of placental mammals
    yolk sac
Card Set
Biology 172 FINAL EXAM: Animal Development
Biology 172 FINAL EXAM: Animal Development