BIO 102 Chapter 23

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Even in the absence of sperm, metabolic activity in an egg can be artificially activated by _____.

A) injection of calcium ions into the cytosol
B) exposure to the low pH of the uterus
C) depletion of its ATP supplies
D) abnormally low levels of extracellular oxygen
E) abnormally high levels of carbonic acid in the cytosol
injection of calcium ions into the cytosol
The formation of the fertilization envelope requires an increase in the availability of _____.
A) potassium ions
B) bicarbonate ions
C) sodium ions
D) calcium ions
E) hydrogen ions
calcium ions
Contact of a sea urchin egg with signal molecules on sperm causes the egg to undergo a brief _____.

A) membrane depolarization
B) acrosomal reaction
C) apoptosis
D) vitellogenesis
E) mitosis
membrane depolarization
Contact of a sperm with signal molecules in the coat of an egg causes the sperm to undergo _____.

A) apoptosis
B) mitosis
C) the acrosomal reaction
D) vitellogenesis
E) depolarization
the acrosomal reaction
During fertilization, the acrosomal contents _____.
A) block polyspermy
B) trigger the completion of meiosis by the sperm
C) digest the protective jelly coat on the surface of the egg
D) nourish the mitochondria of the sperm
E) help propel more sperm toward the egg
digest the protective jelly coat on the surface of the egg
In a newly fertilized egg, the vitelline layer _____.

A) opens the egg's nuclear membrane to allow haploid sperm DNA to enter
B) provides most of the nutrients used by the zygote
C) lifts away from the egg and hardens to form a fertilization envelope
D) secretes hormones that enhance steroidogenesis by the ovary
E) reduces the loss of water from the egg and prevents desiccation
lifts away from the egg and hardens to form a fertilization envelope
In sea urchins, the "fast block" and the longer lasting "slow block" to polyspermy, respectively, are
_____.
A) the jelly coat of the egg and the vitelline membrane
B) inactivation of the sperm acrosome
C) membrane depolarization and the cortical reaction
D) the cortical reaction and the formation of yolk protein
E) the acrosomal reaction and the formation of egg white
membrane depolarization and the cortical reaction
In an egg cell treated with a chemical that binds calcium and magnesium ions, the _____.

A) fertilization envelope would not be formed
B) fusion of sperm and egg nuclei would be blocked
C) acrosomal reaction would be blocked
D) zygote would not contain maternal and paternal chromosomes
E) fast block to polyspermy would not occur
fertilization envelope would not be formed
A human blastomere is _____.

A) a component of the zona pellucida
B) an embryonic cell that is smaller than the ovum
C) that part of the acrosome that opens the egg's membrane
D) a cell that contains a (degenerating) second polar body
E) an embryonic structure that includes a fluid-filled cavity
An embryonic cell that is much smaller than the ovum.
In mammals, the nuclei resulting from the union of the sperm and the egg are first truly diploid
after the _____.
A) activation of the egg
B) initial division
C) completion of spermatogenesis
D) acrosomal reaction
E) completion of gastrulation
initial division
During fertilization, the acrosome _____.
A) digests the coatings surrounding the plasma membrane of the egg
B) injects the sperm nucleus into the egg during fertilization
C) nourishes sperm mitochondria, increasing sperm motility
D) prevents polyspermy by releasing enzymes that destroy surrounding sperm
digests the coatings surrounding the plasma membrane of the egg
Which of the following directors of embryonic development can be found within unfertilized eggs?
A) cytoplasmic determinants
B) mRNAs transcribed from embryonic genome
C) tissue-specific proteins
D) bindin proteins
cytoplasmic determinants
Suppose an antibody to bindin and sea urchin sperm were mixed together and the mixture was
added to eggs. You predict that the antibody-treated sperm will _____.

A) fertilize the eggs normally
B) not bind to the egg membrane
C) not be able to swim toward the egg
D) fertilize eggs from other species
not bind to the egg membrane
During gastrulation, _____.
A) three germ layers form
B) somites form
C) the blastula forms
D) the neural tube forms
three germ layers form
During cleavage, the number of cells _____, while the size of individual cells _____.
A) increases; decreases
B) decreases; increases
C) increases; increases
D) decreases; decreases
increases; decreases
As cleavage continues during frog development, the size of the blastomeres _____.
A) increases as the number of the blastomeres increases
B) decreases as the number of the blastomeres decreases
C) decreases as the number of the blastomeres increases
D) increases as the number of the blastomeres decreases
E) increases, while the number of the blastomeres stays the same
decreases as the number of the blastomeres increases
Gastrulation is an important event in early embryonic development. Which of the following is NOT
a result of gastrulation?
A) the formation of a gastrula
B) formation of three embryonic cell layers
C) the formation of specialized adult tissues
D) movement and alignment of many embryonic cells
the formation of specialized adult tissues
Which of the following correctly displays the sequence of developmental milestones?
A) blastula → gastrula → cleavage
B) gastrula → blastula → cleavage
C) cleavage → blastula → gastrula
D) cleavage → gastrula → blastula
E) blastula →? cleavage → gastrula
cleavage → blastula → gastrula
Cells move to new positions as an embryo establishes its three germ-tissue layers during _____.
A) gastrulation
B) fertilization
C) determination
D) cleavage
E) induction
gastrulation
The outer-to-inner sequence of tissue layers in a post-gastrulation vertebrate embryo is _____.
A) mesoderm → endoderm → ectoderm
B) endoderm → ectoderm → mesoderm
C) ectoderm → mesoderm → endoderm
D) endoderm → mesoderm → ectoderm
E) ectoderm → endoderm → mesoderm
ectoderm → mesoderm → endoderm
If gastrulation was blocked by an environmental toxin, then _____.

A) embryonic germ layers would not form
B) cleavage would not occur in the zygote
C) fertilization would be blocked
D) the blastopore would form above the gray crescent in the animal pole
E) the blastula would not be formed
embryonic germ layers would not form
The vertebrate ectoderm is the origin of the _____.
A) pancreas
B) nervous system
C) kidneys
D) liver
E) heart
nervous system
In frog embryos, the blastopore becomes the _____.
A) ears B) eyes C) mouth D) anus E) nose
anus
In a frog embryo, gastrulation _____.
A) occurs along the primitive streak in the animal hemisphere
B) is impossible because of the large amount of yolk in the ovum
C) proceeds by involution as cells roll over the lip of the blastopore
D) produces a blastocoel displaced into the animal hemisphere
E) occurs within the inner cell mass that is embedded in the large amount of yolk
proceeds by involution as cells roll over the lip of the blastopore
An open space within the gastrula is the _____.
A) mesoderm
B) archenteron
C) neural crest cells
D) endoderm
E) ectoderm
archenteron
From earliest to latest, the overall sequence of early development proceeds in which of the
following sequences?
A) preformation → morphogenesis → neurulation
B) gastrulation → organogenesis → cleavage
C) cleavage → gastrulation → organogenesis
D) gastrulation → blastulation → neurulation
E) ovulation → gastrulation → fertilization
cleavage → gastrulation → organogenesis
Changes in cell position occur extensively during _____.
A) gastrulation
B) fertilization and cleavage, but not during gastrulation
C) gastrulation and cleavage
D) cleavage, but not during gastrulation or organogenesis
E) organogenesis, but not during gastrulation or cleavage
gastrulation and cleavage
Select the choice that correctly associates the organ with its embryonic sources.
A) anterior pituitary gland mesoderm and endoderm
B) skin endoderm and mesoderm
C) thyroid gland mesoderm and ectoderm
D) brain mesoderm and endoderm
E) adrenal gland ectoderm and mesoderm
adrenal gland ectoderm and mesoderm
The first cavity formed during frog development is the _____.
A) anus B) blastopore C) mouth D) blastocoel
Blastocoel
The embryonic precursor to the human spinal cord is the _____.
A) archenteron
B) mesoderm
C) neural tube
D) set of bilateral somites
E) notochord
neural tube
Spina bifida is one of the most prevalent of human birth defects. The defect usually involves the
spinal cord or the spinal canal opening to the outside of the body. Spina bifida results from
problems during the formation of the _____.
A) blastula
B) gastrula
C) somites
D) neural tube
E) notochord
neural tube
Which of the following is the most basic process in the developing embryo because all of the other
processes listed can occur only after it, or in conjunction with it?

A) organogenesis
B) mitosis
C) cell differentiation
D) germ layer formation
E) morphogenesis
mitosis
Which of the following directors of embryonic development can be found within unfertilized eggs?

A) mRNAs transcribed from embryonic genome
B) tissue-specific proteins
C) bindin proteins
D) cytoplasmic determinants
cytoplasmic determinants
Suppose an antibody to bindin was introduced into a chamber containing sea urchin sperm and
eggs. You predict that the antibody-treated sperm will _____.

A) be able to fertilize the eggs normally
B) not be able to swim toward the egg
C) be able to fertilize eggs from other species
D) not be attracted to bind to the egg membrane
not be attracted to bind to the egg membrane
Many amphibian species release their sperm and eggs directly into a watery environment. All of
the following mechanisms might ensure species-specific fertilization in these populations except
_____.
A) blocking of non-species-specific mRNA sequences
B) fertilization envelopes
C) complex coverings of the egg
D) specific protein binding between sperm and egg
E) acrosomal complexes in sperm
blocking of non-species-specific mRNA sequences
The function of the acrosomal complex during fertilization is _____.

A) to permit maximum sperm motility
B) to nourish the sperm mitochondria
C) to dissolve the coating of the egg D) to block polyspermy
to dissolve the coating of the egg
The allele D codes for right-handed coiling in a species of snail, while allele d codes for
left-handed coiling. Assuming the proteins encoded by these two alleles are cytoplasmic
determinants, if a dd female mates with a DD male, what percentage of offspring snails will
develop shells that are left-handed coils?
A) 0% B) 25% C) 50% D) 75% E) 100%
100%
One difference between early development in humans and in Xenopus (frogs) is that _____.

A) in humans, blastocysts implant into the uterine wall; there is no implantation in Xenopus
B) in humans, neurulation occurs immediately after cleavage; in Xenopus, neurulation is delayed
until after gastrulation
C) in humans, there is no formation of the blastula; in Xenopus, the blastula is a critical stage in
early embryogenesis
D) in humans, the yolk sac is much smaller than that seen in Xenopus
E) in humans, gastrulation is delayed as the egg moves along the fallopian tube; in Xenopus,
gastrulation takes place immediately after blastula formation
in humans, blastocysts implant into the uterine wall; there is no implantation in Xenopus
What happens during gastrulation?

A) The blastula forms.
B) The neural tube forms.
C) The three embryonic tissue germ layers form.
D) The somites form.
The three embryonic tissue germ layers form.
During cleavage the size of individual cells _____, while the overall size of the embryo _____.

A) decreases; decreases
B) increases; increases
C) decreases; increases
D) increases; decreases
decreases; increases
During gastrulation in amphibians, the presumptive mesoderm moves into the interior of the
embryo by following fibrils of fibronectin. Given what you know about gastrulation, you predict
that the fibronectin is most likely secreted by which cells?

A) ectodermal cells that line the inside of the blastocoel
B) endodermal cells on the exterior of the embryo
C) mesodermal cells that develop on the inside of the blastocyst
D) endodermal cells that migrate to the inside of the blastocoel
ectodermal cells that line the inside of the blastocoel
Gastrulation is an important event in early embryonic development. Which of the following is Not
a result of this process?

A) movement and alignment of many embryonic cells
B) determination of cell types as a result of cell-cell interactions
C) formation of three embryonic cell layers
D) formation of specialized plant tissues
formation of specialized plant tissues
During organogenesis, the first organ system to begin forming in animal embryos is the _____
system.

A) nervous
B) excretory
C) digestive
D) endocrine
E) circulatory
nervous
The cells of the somites are determined to become all of the following tissues except _____.

A) skin tissue
B) muscle tissue
C) bone tissue
D) connective tissue
E) nervous tissue
nervous tissue
Sperm-egg interactions are species-specific in sea urchins, but not in mammals. What might be one
reason for this difference?

A) Other kinds of signals serve similar functions in mammals.
B) Sea urchin fertilization occurs in open ocean.
C) Sperm have evolved to become more selective in mammals.
D) Sperm-egg recognition relies on egg cytoplasmic components in mammals.
Sea urchin fertilization occurs in open ocean.
Spina bifida is one of the most prevalent of human birth defects. The defect usually involves the
spinal cord or the spinal canal opening to the outside of the body. In severe cases, movement of the
legs may be limited or entirely absent. At which stage of development is this defect likely to occur?
A) formation of the notochord
B) formation of the lateral mesoderm
C) formation of the neural tube
D) formation of the gastrula
E) formation of the somites
formation of the neural tube
What would be one clue that you are observing cell differentiation in a frog embryo?
A) Somites are forming as distinct masses on either side of the neural tube.
B) The embryo has developed a chambered heart.
C) Cells of the lateral mesoderm are undergoing rapid cell division.
D) Cells of the primitive retina are beginning to synthesize pigment molecules
Cells of the primitive retina are beginning to synthesize pigment molecules
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