Card Set Information
As recently as the 18th century, the prevailing theory was called
is the idea that the egg or sperm contains a miniature infant, or “homunculus,” which becomes larger during development
development is determined by
the zygote’s genome and molecules in the egg called cytoplasmic determinants
is the specialization of cells in structure and function
the process by which an animal takes shape
species that are representative of a larger group and easily studied, for example, Drosophila, Mus musculus and Caenorhabditis elegans
Classic embryological studies have focused on the sea urchin, frog, chick, and the nematode C. elegans
Important events regulating development occur during fertilization and the three stages that build the animal’s body, what are the 3 steps?
cell division creates a hollow ball of cells called a blastula
cells are rearranged into a three-layered gastrula
the three layers interact and move to give rise to organs
Fertilization brings the haploid nuclei of sperm and egg together, forming a what?
The sperm’s contact with the egg’s surface initiates metabolic reactions in the egg that trigger the onset of what?
triggered when the sperm meets the egg
at the tip of the sperm releases hydrolytic enzymes that digest material surrounding the egg
sea urchin fertilization
when more than one sperm gets in the egg
Gamete contact and/or fusion depolarizes the egg cell membrane and sets up a fast block to polyspermy
Fast block does not exist in mammals
Fusion of egg and sperm also initiates the what?
the reaction induces a rise in Ca2+ that stimulates what to release their contents outside of the egg
first two steps of the cortical reaction form a fertilization envelope functions as a what?
slow block to polyspermy
In mammalian fertilization, the cortical reaction modifies the zona pellucida, the extracellular matrix of the egg
The sharp rise in Ca2+ in the egg’s cytosol increases the rates of cellular respiration and protein synthesis by the
With these rapid changes in metabolism, the egg is said to be what
The sperm nucleus merges with the egg nucleus and what happens?
cell division begins
rearranges the cells of a blastula into a three-layered embryo, called a gastrula, which has a primitive gut
The three layers produced by gastrulation are called embryonic germ layers which are?
The ectoderm forms the outer layer
The endoderm lines the digestive tract
The mesoderm partly fills the space between the endoderm and ectoderm
Embryos of birds, other reptiles, and mammals develop in a fluid-filled sac in a shell or the uterus
During amniote development, four extraembryonic membranes form around the embryo which are?
The chorion functions in gas exchange
The amnion encloses the amniotic fluid
The yolk sac encloses the yolk
The allantois disposes of waste products and contributes to gas exchange