After fertilization, embryonic development proceeds through ____________, ____________, and ____________.
Cleavage, gastrulation, and organogenesis.
Fertilization
Brings the hapliod nuclei of sperm and egg together to form a diploid zygote. It "activates" the egg.
In the fertilization of mammals, the sperm migrates through the coat of ___________ and binds to receptor molecules in the __________of the egg.
follicle cells, zona pellucida.
In the fertilization of mammals and the binding of sperm to the zona pellucida, the binding induces the ____________, in which the sperm releases__________________ into the zona pellucida.
acrosomal reaction, hydrolytic enzymes.
In mammal fertilization, breakdown of the zona pellucida
by hydrolytic enzymes allows the sperm to reach the _______________of the egg. Membrane proteins of the sperm bind to receptors on the ______________, and the two membranes fuse.
plasma membrane, egg membrane.
In mammal fertilization, after the egg and plasma membranes fuse together, the nucleus and other
components of the sperm cell ____________. This is the _________________.
enter the egg, cortical reaction.
In mammal fertilization, enzymes released during the _______________ harden the ______________, which now functions as a block to polyspermy.
cortical reaction, zona pellucida.
How much of the sperm is taken into the egg in mammal fertilization?
All of the sperm.
In mammal fertilization, the first mitotic division occurs in __________ hours.
12-36 hours.
What follows fertilization in animal development?
Cleavage.
Cleavage
A period of rapid cell division without growth.
Blastomeres
Smaller cells which where all once one big cell of cytoplasm. Come into existence due to cleavage.
What is a blastula?
A single layer of cells that surrounds a large blastocoel cavity.
What does this image depict?
A fertilized egg.
What does the image depict?
The four-cell stage of cleavage.
What does the image depict?
A morula.
What does the image depict?
A blastula.
What is a morula?
A multicellular ball that is surrounded by the fertilization envelope. Is the embryo.
Do mammal eggs have polarity?
No.
What defines the polarity of an egg?
Its distribution of yolk.
What are the two poles of an egg?
The animal pole and the vegetal pole.
What does the animal pole of an egg control?
Development.
What does the vegetal pole of an egg control? Which part of an egg IS this?
Energy, the yolk.
Where does sperm enter an egg?
In the animal pole of the egg.
Changes occur more rapidly in the _______ pole than in the ________ pole.
animal, vegetal.
Cells form from the ________________.
Gray crescent.
Which cleavages are vertical?
1 and 2.
Which cleavages are horizontal?
3
What is meroblastic cleavage?
Incomplete division of the egg.
What types of eggs have meroblastic cleavage?
Yolk-rich eggs like reptiles and birds.
What are the three staes of eroblastic cleavage?
zygote, 4-cell stage, and blastoderm.
What is holoblastic cleavage and what type of species have this?
Complete division of the egg, species whose eggs have little yolk (like sea urchins and frogs) have this.
How many embryonic germ layers are produced by gastrulation?
Three.
What are they three embryonic germ layers produced by gastrulation and where are they located?
The ectoderm is the outer layer of the gastrula. The endoderm lines the embryonic digestive tract. The mesoderm partially fills the space between the endoderm and the ectoderm.
Gastrulation rearranges the cells of a ____________ into a three-layered ___________, called a _____________, that has a primitive gut.
blastula, embryo, gastrula.
Organognesis
The process in which various regions of the three embryonic germ layers develop into the rudiments of organs.
In vertebrates, the ________ forms from mesoderm and the ________ forms from the ectoderm.
notochord, neural plate.
How does the neural tube form?
The neural plate folds and pinches off.
What are amniotes?
Organisms which develip within a fluid-filled sac that is contained within a shell or the uterus. Are the embryos of birds, other reptiles, and mammals.
How many extraembryonic membranes surround amniotic embryos and what are they?
Four. They are amnion, allantois, yolk sac, and chorion.
Amnion
The extraembryonic membrane with protects the embryo in a fluid-filled cavity and prevents dehydration. It also cushions mechanical shock.
Allantois
The extraembryonic membrane which functions as a disposal sac for certain metabolic wastes produced by the embryo. It also functions with the chorion as a respiratory organ.
Yolk Sac
The extraembryonic membrane which expands over the yolk. Blood vessels in it transport nutrients from the yolk to the embryo.
In amniotes, nutients can also be stored in the _________ along with the yolk.
Albumen (egg white).
Chorion
The extraembryonic membrane which exchanges gases with the allantosis between the embryo and the surrounding air.
What type of creatures have extraembryonic membranes?
Amniotes.
True or false: Oxygen and carbon dioxide do not diffuse freely across an egg's shell.
False.
Do the eggs of placental mammals show polarity?
No.
Gastrulation and organogenesis in mammals resembles the processes in what types of animals?
Birds and other reptiles.
What are the four stages in early human embryonic development?
1)The blastocyst reaches the uterus. 2)The blastocyst implants. 3)The extraembryonic membranes begin to form and gastrulation begins. 4)Gastrulation has produced a 3-layered embryo with 4 extraembryonic membranes.
During early cleavage divisions embryonic cells must become ___________.
Different from one another.
What are fate maps?
Territorial diagrams of embryonic development.
When are the axes of the basic body plan set down for nonamniotic vertebrates?
Very early in development, during oogenesis or fertilization.
What does totipotent mean and what type of cell is totipotent?
To be able to differentiate into all cell types found in the adult form of the organizm, the zygote. In amphibians, both blastomeres are as well.
Once embryonic cell division creates cells that differ from each other, the cells begin to ______________.
Influence each other's fates by induction.
What did scientists Spemann and Mangold conclude?
That the dorsal lip of the blastopore functions as an organizer of hte embryo.
When the dorsal lip of one embryo is grafted to the ventral surface of another embryo, 2 notochords and neural tubes formed (2 embryos are joined). How are the embryos joined?
Belly to belly.
Induction plays a major role in __________________.
Pattern formation.
Positional information tells a cell where it is ____________________________.
Relative to the animal's body axes.
Limbs begin as _________.
Limb buds.
What are teh two limb bud organizer regions?
AER and ZPA.
What does AER secrete?
FGF
AER is required for pattern formation long what axis?
dorsal-ventral and proximal-distal axis.
Cells with the most FGF are located along AER's what?
Apical epidermal ridge.
What does ZPA secrete?
Sonic hedgehog.
What is sonic hedgehog?
A protein growth factor.
More ZPA creates something that is ___________. Less ZPA creates something that is ____________.
Posterior, anterior.
What would happen if we removed AER?
We wouldn't be able to make fingerlike objects.
What would happen if we turned AER?
Proximal/Distal would have no change but dorsal/ventral switches.
What would happen if we had 2 ZPA?
We would have pinkylike fingers on both ends of our hands.
