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103 Cards in this Set

  • Front
  • Back
What was the main belief of preformation?
a miniature adult is present in the sperm or egg, waiting to unfold
In epigenesis, what two facts are known about the embryo?
it is a new creation that develops and differentiates in a step by step manner and it has new parts produced in it that were not in the zygote
What is the main belief in the hierarchy of developmental decisions?
life begins with the zygote and progresses by dividing mitotically
What are the 6 stages of development in order?
1) gamete formation
2) fertilization
3) cleavage
4) gastrulation
5) organogenesis
6) growth
What occurs in gamete formation?
the sperm and eggs form and mature
What occurs in fertilization?
the egg and sperm fuse
What occurs in cleavage?
th zygote subdivides and determinants are partitioned in blastomeres
What occurs in gastrulation?
germ layers form
What occurs in organogenesis?
body organs form and cells interact and differentiate
What occurs in the growth stage of development?
organs increase in size and the adult body form is attained
What is the effect on the size of the egg during oocyte maturation?
the egg increases in size
What does the egg cytoplasm contain and what are these products required for?
mRNA, ribosomes, and tRNA; required for protein synthesis
What is the purpose of the morphogenetic determinants?
they direct early development
Where are the morphogenetic determinants located?
in the egg cytoplasm
What are the two functions of metabolic inhibitors?
1) maintain egg in a quiescent state
2) inhibit translation of mRNA
What stage is the egg in when it is first formed?
Prophase I of Meiosis I
What must occur for Meiosis II to be completed?
the egg must be fertilized
What is fertilization?
the union of egg and sperm that restores the diploid chromosome number
How does fertilization activate egg development?
by removing the metabolic inhibitors
What do many marine eggs release to attract sperm of the same species?
a chemotactic molecule
What is the path of sea urchin sperm?
through the jelly layer and then through the vitelline envelope
What do the egg-recognition proteins on sperm bind to?
species-specific sperm receptors on the V.E.
What occurs when the sperm binds to the V.E.?
a fertilization cone appears
What occurs after the fertilization cone appears?
a "fast block" prevents the entrance of additional sperm
What is the "fast block"?
an electrical potential that spreads over the membrane
What follows the "fast block"?
a cortical reaction
What 4 events occur during the cortical reaction?
1) granules in the egg cortex fuse with the plasma membrane
2) the granules release enzymes between the plasma membrane and V.E.
3) the V.E. is lifted away
4) the V.E. hardens, becoming the fertilization membrane
What occurs after the cortical reaction?
the male and female pronuclei fuse
What does the fusion of the pronuclei remove?
the metabolic inhibitors
What occurs in the egg following removal of the metabolic inhibitors?
a burst of DNA and protein synthesis
What is the protein synthesis in eggs directed by?
maternal mRNA stored in the cytoplasm
What does fertilization initiate?
reorganization of cytoplasm
What does fertilization reposition?
determinants that begin development and cleavage
What is cleavage?
a series of early mitotic cell division
What increases in cleavage?
the number of cells
What doesn't increase in cleavage?
the size of the organism
What does the size of the organism not exceed?
the size of the zygote
What are produced during cleavage?
the blastomeres
What two factors determine the pattern of cleavage?
1) the quantity and distribution of yolk present
2) genes controlling the symmetry of cleavage
What are two characteristics of isolecithal eggs?
1) very little yolk
2) yolk evenly distributed in cytoplasm
What are 3 examples of animals with isolecithal eggs?
echinoderms, molluscs, and mammals
What are two characteristics of mesolecithal eggs?
1) moderate amount of yolk
2) yolk concentrated in the vegetal pole
What is an example of animals who have mesolecithal eggs?
What are two characteristics of telolecithal eggs?
1) large amount of yolk
2) yolk concentrated at the vegetal pole
What are 4 examples of animals who have telolecithal eggs?
birds, reptiles, most fish, few amphibians
What are two qualities of holoblastic cleavage?
1) it occurs in isolecithal and mesolecithal eggs
2) the cleavage furrow extends completely through the egg
What are three qualities of meroblastic cleavage?
1) it occurs in telolecithal eggs
2) the cleavage furrow doesn't cut through the heavy yolk in the vegetal pole
3) division is confined to a narrow disc-shaped mass on the yolk
What are the 4 major cleavage patterns of isolecithal eggs?
radial, spiral, bilateral, and rotational
In radial cleavage, what does the first series of cleavage divisions produce?
lightly touching blastomeres stacked on top of each other
What can occur if the blastomeres produced in radial cleavage separate?
each blastomere can direct its own development into a normal embryo
Which type of development occurs in radial cleavage?
regulative development
What is the position of the cleavage planes in spiral cleavage?
oblique to the animal-vegetal axis
Where are the cells tiers that are produced in spiral cleavage located?
in the cleavage furrows of existing cells
What two actions can occur if the cell tiers are separated in spiral cleavage?
development stops or abnormal embryos are produced because blastomeres aren't capable of directing own development
Which type of development occurs in spiral cleavage?
mosaic development
In which organisms does bilateral cleavage occur?
tunicates (sea squirts)
In bilateral cleavage, what is determined before fertilization and why?
the anterior-posterior axis; because of unequal distribution of cytoplasmic components
In which organisms does rotational cleavage occur?
Where does the 1st rotational cleavage plane cut through?
the animal/vegetal axis
What occurs in the 2nd rotational cleavage plane?
one blastomere divides meridianally while the other divides equatorially
What is the product of rotational cleavage?
an odd number of cells
What is a blastula?
a hollow ball of cells produced by cleavage divisions
In mammals, what is the blastula called?
a blastocyst
What is gastrulation?
the conversion of blastula into a gastrula, a complex structure with 3 tissue layers
What occurs with the blastomeres in gastrulation?
they migrate to positions to establish the embryonic body plan
What is the coelom?
a true body cavity lined by mesoderm
What does the mesoderm contain?
the viscera
What are the two types of coelom formation?
schizocoelous and enterocoelous
What does the coelom form from in schizocoelous formation?
the splitting of the mesoderm
What does the coelom form from in enterocoelous formation?
outpockets of the archenteron
Which tissue layer is the nervous system derived from?
What are the three primary tissue layers?
ectoderm, endoderm, and mesoderm
What are three functions of the coelom?
1) provides a tube within a tube arrangement
2) permits greater size and complexity
3) provides space for specialization of organs
What is the Roux-Weismann hypothesis?
nuclear division "breaks up" the genome into smaller units which are parceled out to cells; each cell only receives the genetic information for its characteristics
Who disproved the Roux-Weismann hypthesis?
Hans Spemann
What two results were obtained from Spemann's experiments?
1) all cells contain the same genetic information
2) cytoplasm in the area of the gray crescent contains info essential for normal development
How are cytoplasmatic components distributed in a zygote?
What determines the cell fate?
morphogenetic determinants
What does yellow cytoplasm form?
muscle cells
What does gray equatorial cytoplasm form?
notochord and neural tube cells
What does clear cytoplasm form?
larval epidermis cells
What does gray vegetal cytoplasm form?
gut cells
What is embryonic induction?
the capacity of some cells to evoke a specific developmental response in others
What does primary induction set in motion?
secondary inductions
What three events does the induction sequence include?
1) cell movement
2) changes in adhesion
3) cell proliferation
How is protein synthesis controlled during development?
from cleavage to mid-blastula stage--controlled by maternal mRNA
afterward--controlled by zygote
Which three types of organisms do amniotes include?
birds, reptiles, and mammals
What did the evolution of the shelled amniotic egg make a requirement?
internal fertilization
What are the two functions of the amnion?
surrounds embryo/fetus and secretes amniotic fluid
Which extraembryonic membrane of the shelled amniotic egg pre-dates amniotes by millions of years?
the yolk sac
What are the two functions of the allantosis?
storing metabolic wastes and serving as a respiratory surface
Which structure encloses all of the other extraembryonic membranes?
the chorion
Where is the chorion located?
beneath the egg shell
What does the chorion act as?
a respiratory surface for gas exchange
What does the chorioallantoic membrane serve as?
a respiratory surface
What are monotremes?
primitive mammals that lay eggs
What are the two monotremic animals?
the spiny anteater and the duck-billed platypus
How do marsupial embryos develop?
they develop in the uterus, but dont' implant in the uterus; embryos emerge from the uterus and finish developing in an external pouch
In placental mammals, where do the young develop?
in the uterus
What modifications have occurred in the amnion?
What modification has been made to the chorion?
it now has a maternal contribution to the placenta
What modification has been made to the allantosis in placental mammals?
it contributes to the formation of the umbilical cord
What modification has been made to the yolk sac in placental mammals?
it doesn't contain yolk, but it serves as a source of stem cells that give rise to blood and lymphoid cells