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Worksheets104 Embryonic Development
Total questions: 21
Worksheet time: 11mins
Repeated cell divisions of the zygote during the earliest embryonic development is known as:___________.
Fertilization
Cleavage
oogenesis
spermatogensis
Which of the following sequences represents the correct order of events in the formation of a human fetus?
Zygote → Blastocyst → Embryo → Fertilization
Fertilization → Zygote → Blastocyst → Embryo
Blastocyst → Embryo → Differentiation → Zygote
Fertilization → Growth → Differentiation → Zygote
The embryo layer that forms the skin and nervous tissue is the _____.
endoderm
mesoderm
ectoderm
deuterostome
The innermost layer of the blastocyst is the
endoderm
gastrula
ectoderm
mesoderm
The middle layer of the blastocyst is the
endoderm
ectoderm
mesoderm
deuterostome
What is the next event after cleavage during embryonic development?
infolding of the blastula leading to gastrulation
cells migrating to the outside to form a hollow ball of cells - the blastula.
maternal/cytoplasmic determinants differentiating cells
axis induction by the sperm entry point.
Which of the following determines the axes of the future animal?
uneven distribution of the maternal/cytoplasmic determinants (generally the anterior side will be where there are more maternal/cytoplasmic determinants.
the position of the egg within the uterus will determine which side will be the anterior side (faces up in the uterus) and which will be the posterior side (faces down in the uterus).
the sperm entry point and the rotation of the cortex will expose the gray crescent which will become the future dorsal side.
once the anterior-posterior and ventral-dorsal axes are established, the left-right axes are determined automatically.
What activates the maternal/cytoplasmic determinants?
an electric shock generated by the sperm entry
release of Calcium ions stored in the cortex of the egg
the sperm entering the egg and releasing an egg activator molecule
the rotation of the cortex towards the sperm entry point
What is the role of the maternal/cytoplasmic determinants?
they determine which genetic traits from the mother are passed on to the developing offspring
they tell the cleavage cells to migrate to the outside to form the blastula
they initiate gastrulation
they turn on the very first set of homeotic genes necessary for the earliest development
How do the cleavage cells forming the blastula and later the cells migrating to form the gastrula move?
they move with flagella
they move with pseudopods
they move with cilia
they use all three modes of cellular locomotion depending on their position and how far they have to move.
Which of the following are ways of morphogenesis in the developing embryo
cells change their shape in unison in order to create a new shape together
cells strategically die to create a hollow space
cells wedge to create stretched, bigger shapes
All of the above
Which concept of embryonic development is depicted in this image?
cell to cell induction
gastrulation
morphogenesis
egg activation
Cortical Rotation exposes the gray crescent. What is the significance of the gray crescent?
It is the point where the future blastopore will be.
It is the point where the anterior side of the anterior-posterior axis will be.
It the point where the dorsal side of the ventral-dorsal axis will be.
It the point where the brain (gray matter) will first develop.
Maternal/Cytoplasmic determinants start the earliest differentiation. How do cells in the later embryo decide how to further differentiate?
position - for example, ectoderm cells will not differentiate to become muscle cells because they are located on the outside of the developing embryo.
cell to cell communication - cells communicate with one another to determine their position and which steps are needed to further differentiate. For example, a cell in the position of the pancreatic bud will be at the interface between endoderm and mesoderm approximately in the middle of the embryo, The cell will determine its position by communicating with the cells around itself.
cell to cell induction - special groups of cells will produce gene products that direct the further differentiation of the surrounding cells. A great example is the ZPA which directs limb development with the sonic hedgehog protein.
What is the process by which cells become committed to a particular fate?
differentiation
determination
egg activation
pattern formation and morphogenesis
What is the process by which cells organize themselves to assume a particular shape?
differentiation
determination
egg activation
morphogenesis
