Bio 116 Exam 4 Questions and Answers 100% Pass

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Bio 116 Exam 4 Questions and Answers
100% Pass



In animal development, which of the following best describes the process of cleavage? -
ANS Mitosis



What are the cells created by cleavage called? - ANS Blastomeres



Which of the following are the three germ layers contained in the gastrula? - ANS Ectoderm,
mesoderm, endoderm


Which of the following stages of development is defined by the three embryonic tissue layers
(ectoderm, mesoderm, and endoderm)? - ANS Gastrula



What happens to a cell during the process of differentiation? - ANS It undergoes a change
toward a more specialized form or function.


A child is born without a fully developed pancreas. He is normal in all other respects, and thus
doctors believe that the problem most likely began early in development. During which of the
following processes did the original error most likely occur? - ANS Endoderm formation


True or false? Early animal development progresses through distinct stages: first the production
of the zygote through fertilization, then cleavage, then the formation of the gastrula, and then
the formation of the blastula. - ANS false



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After fertilization, embryonic development progresses through three stages:
cleavage, during which the zygote develops into a blastula through extensive cell division;
gastrulation, during which three tissue layers are established by the dramatic rearrangement of
cells, forming a gastrula;
organogenesis, during which the rudiments of organs develop.
The details of embryonic development vary by species, but the developmental sequence is
consistent. Embryonic development has been studied extensively in a few species, including sea
urchins, frogs, and chickens. All the images in this tutorial are based on frog development.


Part A - Differentiating between cleavage, gastrulation, and organogenesisPart complete
Determine which terms, phrases, and images describe each phase of development.

Drag each item to the appropriate bin. - ANS cleavage:
-blastula
-cytoplasm partitioned into many cells
-picture without the layers


gastrulation:
-embryonic germlayers form
-blastopore
-gastrula
-colorful picture


organogenesis:
-neural tube
-organs begin to develop from germ layers
-somites


Part B - Gastrulation in a frog embryoPart complete

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Gastrulation is the stage of embryonic development following cleavage. During gastrulation,
cell division slows dramatically, and cells are rearranged in a precise way, forming three germ
layers. The diagram below illustrates gastrulation in a frog embryo, represented in cross
section.
Drag the labels to their appropriate locations on the diagram. Use only pink labels for pink
targets. Not all labels will be used. - ANS A. blastocoel
B. primitive gut (archenteron)
C. ectoderm
D. mesoderm
E. endoderm
F. blastopore
G. yolk plug
H. blastopore forms
I. primitive gut begins to form
J. three germ layers in place


Part C - Organogenesis in a frog embryoPart complete
Tissue and organ formation begins during the process of organogenesis.
Which five of the following statements are true about organogenesis in a frog embryo? -
ANS -The notochord does not persist in adult frogs.
-The neural tube forms from ectoderm and develops into the central nervous system.
-Somites form along the length of the notochord and neural tube.
-The endoderm gives rise to the lining of the frog's digestive tract.
-Some somite cells migrate to other locations in the developing embryo.



In sea urchins, the process of fertilization produces a(n) _____. - ANS zygote



What is the cortical reaction? - ANS the formation of a fertilization envelope that bars
additional sperm from entry into the egg

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As cleavage continues, a zygote forms into a solid multicellular ball called a(n) _____. -
ANS morula


Several hours after fertilization, cleavage results in the formation of a hollow ball of cells called
a _____. - ANS blastula



The three-layered embryo is the _____. - ANS gastrula



The _____ eventually develops into the sea urchin's digestive tract. - ANS archenteron



During gastrulation, invagination occurs at the _____. - ANS blastopore



In vertebrates, the ectoderm gives rise to the _____. - ANS outer layer of skin


In an embryonic vertebrate, the zone of polarizing activity (ZPA) is a block of tissue located on
the posterior side of a limb bud. The ZPA provides information about the anterior-posterior axis
of the limb. Cells nearest the ZPA form the most posterior of digits (like our little finger); cells
farthest from the ZPA form the most anterior digits (like our thumb).
How would a vertebrate forelimb bud develop if it had two zones of polarizing activities, one on
the posterior side and one on the anterior side of the bud? - ANS The forelimb bud would
develop with extra digits, in a mirror image arrangement to the normal digits.


In an embryonic vertebrate, the apical ectodermal ridge (AER) is a thickened area at the tip of
the bud. The cells of the AER secrete protein signals that promote limb-bud outgrowth, and
removing the AER blocks growth of the limb along the proximal-distal axis. How would the
forelimb of an embryo develop if the AER was removed early or late in limb development? -
ANS Early removal of the AER would prevent the formation of many distal structures,
whereas late removal of the AER would prevent the formation of a few distal structures.




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