Chapter 47 Questions

Question 1

Choose the correct developmental sequence of animal development.

a. gastrulation → cleavage → fertilization → organogenesis
b. cleavage → fertilization → gastrulation → organogenesis
c. fertilization → cleavage → gastrulation → organogenesis
d. cleavage → gastrulation → organogenesis → fertilization
e. organogenesis → cleavage → fertilization → gastrulation

Answer 1

c. fertilization → cleavage → gastrulation → organogenesis

Question 2

Among the following, the earliest consequence of the acrosomal reaction is _____.

a. the cortical reaction
b. the slow block to polyspermy
c. cleavage
d. the membrane of the egg depolarizing
e. the development of the fertilization envelope

Answer 2

d. the membrane of the egg depolarizing

Question 3

The first stage of embryonic development is _____. This process produces _____.

a. parturition … a fetus
b. ovulation … a zygote
c. neurulation … a neurula
d. cleavage … a cluster of cells
e. gastrulation … a three-layered embryo

Answer 3

d. cleavage … a cluster of cells

Question 4

The uneven cleavage of cells early in the development of the yolk-rich embryos of birds is called _____.

a. holoblastic cleavage
b. meroblastic cleavage
c. gastrulation
d. neurulation
e. organogenesis

Answer 4

b. meroblastic cleavage

Question 5

The mesoderm gives rise to _____.

a. the central nervous system
b. the lining of the lungs
c. skeletal and muscular systems
d. jaws and teeth
e. the gastrointestinal tract and pancreas

Answer 5

c. skeletal and muscular systems

Question 6

Birds, reptiles, and mammals are called “amniotes” because _____.

a. they transport oxygen to the embryo
b. they have extra-embryonic membranes that develop an aqueous environment in which development occurs
c. they give rise to cells that form the nervous system
d. their embryos lack an allantois to collect and store metabolic wastes
e. they digest yolk and form a network of blood vessels to distribute nutrients to the embryo

Answer 6

b. they have extra-embryonic membranes that develop an aqueous environment in which development occurs

Question 7

During the early development of a human embryo, the _____ eventually forms the _____.

a. blastocoel … archenteron
b. hypoblast … amniotic cavity
c. trophoblast … embryo proper
d. epiblast … placenta
e. epiblast … ectodermal, mesodermal, and endodermal tissues

Answer 7

e. epiblast … ectodermal, mesodermal, and endodermal tissues

Question 8

Embryonic cells especially active in assuring nutritional exchange between a pregnant woman and her embryo are found in the _____.

a. trophoblast
b. ectoderm
c. hypoblast
d. epiblast
e. inner cell mass

Answer 8

a. trophoblast

Question 9

An embryonic cell that is “totipotent” is one that can _____.

a. by itself, give rise to the entire embryo, as cleavage proceeds
b. move mesoderm cells in the blastocoel
c. redistribute yolk from the vegetal to the animal pole of the frog embryo
d. organize the blastula
e. migrate into the center of the blastula during gastrulation

Answer 9

a. by itself, give rise to the entire embryo, as cleavage proceeds

Question 10

The cortical reaction of sea urchin eggs functions directly in

a. the formation of a fertilization envelope.
b. the production of a fast block to polyspermy.
c. the release of hydrolytic enzymes from the sperm.
d. the generation of an electrical impulse by the egg.
e. the fusion of egg and sperm nuclei.

Answer 10

a. the formation of a fertilization envelope.

Question 11

Which of the following is common to the development of both birds and mammals?

a. gray crescent
b. holoblastic cleavage
c. epiblast and hypoblast
d. trophoblast
e. yolk plug

Answer 11

c. epiblast and hypoblast

Question 12

The archenteron develops into

a. the endoderm.
b. the placenta.
c. the mesoderm.
d. the blastocoel.
e. the lumen of the digestive tract.

Answer 12

e. the lumen of the digestive tract.

Question 13

What structural adaptation in chickens allows them to lay their eggs in arid environments rather than in water?

a. yolk
b. gastrulation
c. development of the brain from ectoderm
d. cleavage
e. extraembryonic membranes

Answer 13

e. extraembryonic membranes

Question 14

In humans, identical twins are possible because

a. early blastomeres can form a complete embryo if isolated.
b. the gray crescent divides the dorsal-ventral axis into new cells.
c. convergent extension occurs.
d. extraembryonic cells interact with the zygote nucleus.
e. cytoplasmic determinants are distributed unevenly in unfertilized eggs.

Answer 14

a. early blastomeres can form a complete embryo if isolated.

Question 15

Cells transplanted from the neural tube of a frog embryo to the ventral part of another embryo develop into nervous system tissues. This result indicates that the transplanted cells were

a. apoptotic.
b. totipotent.
c. mesenchymal.
d. determined.
e. differentiated.

Answer 15

d. determined.

Question 16

Select the correct statement about embryonic development in a frog.

a. Development from zygote to blastula involves mitotic division, cell movement, and cell growth.
b. The blastocoel of a developing frog embryo develops into the digestive tract.
c. The reorganization of cell layers during gastrulation allows the layers to interact with each other in new ways.

Answer 16

c. The reorganization of cell layers during gastrulation allows the layers to interact with each other in new ways.

Question 17

The allantois stores nitrogenous wastes in a reptile egg. What is the function of the allantois in human development?

a. The allantois cushions the human embryo in a private “pond” during development.
b. The allantois helps form the umbilical cord in human development.
c. The allantois does not play any role in human development, because the placenta mediates the transfer of nitrogenous wastes from embryonic to maternal circulation.

Answer 17

b. The allantois helps form the umbilical cord in human development.

Question 18

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?

a. 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.
b. Early removal of the AER would prevent the development of a forelimb, whereas late removal of the AER would not have any effect.
c. Early or late removal of the AER would have the same result: the embryo would not develop a forelimb.

Answer 18

a. 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.

Question 19

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).
Figure.
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?
a. The forelimb bud would develop with extra digits, in a mirror image arrangement to the normal digits.
b. The embryo wouldn’t develop a forelimb.
c. The forelimb bud would develop into a hind limb.

Answer 19

a. The forelimb bud would develop with extra digits, in a mirror image arrangement to the normal digits.

Question 20

Fertilization of an egg without activation is most like ___.

a. placing the key in the ignition of a car but not starting the engine
b. resting during halftime of a basketball game
c. walking to the cafeteria and eating lunch
d. preparing a pie from scratch and baking it in the oven

Answer 20

a. placing the key in the ignition of a car but not starting the engine

Question 21

In an egg cell treated with a chemical that binds calcium and magnesium ions, the ___.

a. fusion of sperm and egg nuclei would be blocked
b. fertilization envelope would not be formed
c. fast block to polyspermy would not occur
d. acrosomal reaction would be blocked

Answer 21

b. fertilization envelope would not be formed

Question 22

In order to test how sea urchin sperm bind to eggs, scientists isolated the egg receptor protein that binds to the sperm acrosomal protein called bindin. Plastic beads were coated with egg receptor for bindin (ERB1) from eggs of the sea urchin Strongylocentrotus purpuratus, and then the beads mixed with sperm from S. purpuratus or from the related species, S. franciscanus. The researchers counted how many sperm were bound to each bead. The results are shown in the graph below.
Treatments:
A: S. purpuratus sperm mixed with S. purpuratus ERB1 beads.
B: S. purpuratus sperm mixed with beads conaining no ERB1 beads.
C: S. franciscanus sperm mixed with S. purpuratus ERB1 beads.
D: S. franciscanus sperm mixed with beads containing no ERB1 protein
Graph.
Based on the description of the experiment, which of the treatments would be considered a “control” treatment for S. purpuratus sperm binding?
a. Treatment A
b. Treatment B
c. Treatment C
d. Treatment D

Answer 22

b. Treatment B

Question 23

In order to test how sea urchin sperm bind to eggs, scientists isolated the egg receptor protein that binds to the sperm acrosomal protein called bindin. Plastic beads were coated with egg receptor for bindin (ERB1) from eggs of the sea urchin Strongylocentrotus purpuratus, and then the beads mixed with sperm from S. purpuratus or from the related species, S. franciscanus. The researchers counted how many sperm were bound to each bead. The results are shown in the graph below.
Treatments:
A: S. purpuratus sperm mixed with S. purpuratus ERB1 beads
B: S. purpuratus sperm mixed with beads containing no ERB1 protein
C: S. franciscanus sperm mixed with S. purpuratus ERB1 beads
D: S. franciscanus sperm mixed with beads containing no ERB1 protein
Graph.
What is a broader implication from the observations of the experiment?
a. Only some species of sea urchins use receptor proteins on their eggs to bind sperm.
b. In sea urchins, fertilization of eggs by sperm is dependent upon species-specific protein interactions.
c. S. franciscanus is probably not a sea urchin, but must be some other type of organism.
d. Protein-coated plastic beads should not be used to test sperm binding to eggs.

Answer 23

b. In sea urchins, fertilization of eggs by sperm is dependent upon species-specific protein interactions.

Question 24

At the moment of sperm penetration, human eggs ___.

a. have used flagellar propulsion to move from the ovary to the oviduct
b. are still surrounded by follicular cells
c. have a paper-thin cell of calcium carbonate that prevents desiccation
d. are still located within the ovary

Answer 24

b. are still surrounded by follicular cells

Question 25

Among these choices, the largest cell involved in frog reproduction is ___.

a. an egg
b. a blastomere in the animal pole
c. one of the products of the first cleavage
d. a blastomere in the vegetal pole

Answer 25

a. an egg

Question 26

In which of the following organisms does holoblastic cleavage typically occur?
I. sea urchins
II. humans
III. birds
IV. fish
a. both II and IV
b. I only
c. both I and III
d. both I and II

Answer 26

d. both I and II

Question 27

In some rare salamander species, all individuals are females. Reproduction relies on those females having access to sperm from males of another species. However, the resulting embryos receive no genetic contribution from the males. Why do you think sperm are necessary for reproduction?

a. Sperm are necessary to produce a diploid zygote.
b. Cell differentiation is initiated by the sperm.
c. Sperm trigger egg activation.
d. The sperm allow morphogenesis to proceed.

Answer 27

c. Sperm trigger egg activation.

Question 28

From earliest to latest, the overall sequence of early development proceeds in which of the following sequences?

a. cortical reaction -> acrosomal reaction -> first cell division -> synthesis of embryo’s DNA begins
b. acrosomal reaction -> cortical reaction -> synthesis of embryo’s DNA begins -> first cell division
c. first cell division -> synthesis of embryo’s DNA begins -> acrosomal reaction -> cortical reaction
d. cortical reaction -> synthesis of embryo’s DNA begins -> acrosomal reaction -> first cell division

Answer 28

b. acrosomal reaction -> cortical reaction -> synthesis of embryo’s DNA begins -> first cell division

Question 29

An embryo with meroblastic cleavage, extraembryonic membranes, and a primitive streak must be that of ___.

a. an insect
b. a bird
c. an amphibian
d. a sea urchin

Answer 29

b. a bird

Question 30

If gastrulation was blocked by an environmental toxin, then ___.

a. embryonic germ layers would not form
b. the blastopore would form above the gray crescent in the animal pole
c. cleavage would not occur in the zygote
d. the blastula would not be formed

Answer 30

a. embryonic germ layers would not form

Question 31

Thalidomide, now banned for use as a sedative during pregnancy, was used in the early 1960s by many women in their first trimester of pregnancy. Some of these women gave birth to children with limb and organ deformities, suggesting that the drug most likely influenced ___.

a. early cleavage divisions
b. morphogenesis
c. gastrulation
d. differentiation of bone tissue

Answer 31

b. morphogenesis

Question 32

Cell migration occurs extensively during ___.

a. cleavage, but not during gastrulation or organogenesis
b. both gastrulation and organogenesis
c. gastrulation and cleavage
d. organogenesis, but not during gastrulation or cleavage

Answer 32

b. both gastrulation and organogenesis

Question 33

Why was the evolution of the extraembryonic membranes crucial for colonization of land by the vertebrates? Extraembryonic membranes ____.

a. provide an aqueous environment for embryo development
b. give rise to crucial organ systems, like the heart and brain
c. direct morphogenesis within the embryo
d. provide nutrients that produce energy for development

Answer 33

a. provide an aqueous environment for embryo development

Question 34

In humans, identical twins are possible because ___.

a. the gray crescent divides the dorsal-ventral axis into new cells
b. cytoplasmic determinants are distributed unevenly in unfertilized eggs
c. early blastomeres can from a complete embryo if isolated
d. extraembryonic cells interact with the zygote nucleus

Answer 34

c. early blastomeres can from a complete embryo if isolated

Question 35

Cells transplanted from the neural tube of a frog embryo to the ventral part of another embryo develop into nervous system tissues. This result indicates that the transplanted cells were ___.

a. mesenchymal
b. differentiated
c. determined
d. totipotent

Answer 35

c. determined

Question 36

Just prior to the onset of gastrulation in an embryo, the “organizer” cells are specified. If you were to experimentally block the specification of these cells, what would you expect the result to be in the developing embryo?

a. The body axes would develop normally, but the embryo would not grow appendages.
b. Gastrulation would not occur, and normal development would cease.
c. The embryo would not develop an intestine, but all other organs and tissues would develop normally.
d. There would be no effect on development.

Answer 36

b. Gastrulation would not occur, and normal development would cease.

Question 37

The formation of the fertilization membrane and the slow block to polyspermy are dependent on

a. the entrance of potassium ions into the egg.
b. the departure of sodium ions from the egg.
c. the entrance of calcium ions into the egg.
d. the departure of hydrogen ions from the egg.

Answer 37

c. the entrance of calcium ions into the egg.

Question 38

Diploidy is first reestablished following

a. fertilization.
b. gastrulation.
c. parthenogenesis.
d. organogenesis.
e. ovulation.

Answer 38

a. fertilization.

Question 39

Development must occur in the order of which of the following sequences?

a. fertilization → cleavage → blastula → organogenesis gastrula
b. fertilization → cleavage → blastula → gastrula → organogenesis
c. cleavage → blastula → gastrula → fertilization → organogenesis
d. gastrula → organogenesis → blastula → cleavage → fertilization
e. organogenesis → cleavage → gastrula → blastula → fertilization

Answer 39

b. fertilization → cleavage → blastula → gastrula → organogenesis

Question 40

In humans, identical twins are produced by the separation of cells during

a. gastrulation.
b. organogenesis.
c. pattern formation.
d. blastomere cleavage.
e. the development of the notochord.

Answer 40

d. blastomere cleavage.

Question 41

The anatomical axis that is largely symmetrical in nematodes, echinoderms, and vertebrates is

a. right to left.
b. dorsal to ventral.
c. anterior to posterior.
d. animal to vegetal.

Answer 41

a. right to left.

Question 42

The cavity inside the blastula is called the

a. gastrula.
b. archenteron.
c. blastomere.
d. animal pole.
e. blastocoel.

Answer 42

e. blastocoel.

Question 43

The term convergent extension describes a process of morphogenetic movement in which a sheet of cells

a. becomes shorter and wider.
b. invaginates.
c. becomes narrow and longer.
d. evaginates.
e. migrates

Answer 43

c. becomes narrow and longer.

Question 44

Which is true about the experimental group in Spemann’s experiment with two-blastomere stage salamander embryos?

a. Some blastomeres that received none of the gray crescent formed normal embryos, but some formed abnormal embryos with only the ventral side.
b. All blastomeres formed normal embryos.
c. Some blastomeres that received none of the gray crescent formed normal embryos, but some formed abnormal embryos with only the dorsal side.
d. All blastomeres that received none of the gray crescent formed abnormal embryos with only the ventral side.
e. The experiment resulted in embryos with two sets of body axes and structures.

Answer 44

d. All blastomeres that received none of the gray crescent formed abnormal embryos with only the ventral side.

Question 45

The apical ectodermal ridge (AER) secretes fibroblast growth factor (FGF), which functions in which of the following ways?

a. It promotes growth of the limb bud along the proximal-distal axis.
b. It regulates the development of the limb bud along the anterior-posterior axis.
c. It determines whether a limb bud becomes a forelimb or hind limb.
d. It prevents situs inversus.

Answer 45

a. It promotes growth of the limb bud along the proximal-distal axis.

Question 46

Which is the correct order of events between the release of gametes into the water and fertilization in sea urchins?

1. Egg’s jelly coat is digested.
2. Sperm head contacts the egg surface.
3. Soluble molecules from egg jelly coat attract sperm.
4. Fusion of sperm and egg plasma membranes occurs.
5. Hydrolytic enzymes are discharged from the acrosome.
6. The acrosomal process is formed.
7. Protein molecules on the acrosomal process bind receptor proteins in the egg plasma membrane.
8. The acrosomal process penetrates the egg jelly coat.
   a. 1, 2, 3, 4, 5, 6, 7, 8
   b. 1, 3, 2, 4, 8, 5, 6, 7
   c. 3, 2, 5, 1, 6, 8, 7, 4
   d. 3, 2, 5, 1, 6, 7, 4, 8

Answer 46

c. 3, 2, 5, 1, 6, 8, 7, 4

Question 47

Which embryonic germ layer is incorrectly matched with one of its derivatives?

a. endoderm—nervous and sensory systems
b. mesoderm—excretory and reproductive systems (excluding germ cells)
c. ectoderm—jaws and teeth

Answer 47

a. endoderm—nervous and sensory systems

Question 48

The cortical reaction of sea urchin eggs functions directly in

a. the formation of a fertilization envelope.
b. the production of a fast block to polyspermy.
c. the generation of an electrical impulse by the egg.
d. the fusion of egg and sperm nuclei.

Answer 48

a. the formation of a fertilization envelope.

Question 49

Which of the following is common to the development of both birds and mammals?

a. holoblastic cleavage
b. epiblast and hypoblast
c. trophoblast
d. gray crescent

Answer 49

b. epiblast and hypoblast

Question 50

The archenteron develops into

a. the mesoderm.
b. the endoderm.
c. the placenta.
d. the lumen of the digestive tract.

Answer 50

d. the lumen of the digestive tract.

Question 51

What structural adaptation in chickens allows them to lay their eggs in arid environments rather than in water?

a. extraembryonic membranes
b. yolk
c. cleavage
d. gastrulation

Answer 51

a. extraembryonic membranes

Question 52

If an egg cell were treated with EDTA, a chemical that binds calcium and magnesium ions,

a. the acrosomal reaction would be blocked.
b. the fusion of sperm and egg nuclei would be blocked.
c. the fast block to polyspermy would not occur.
d. the fertilization envelope would not form.

Answer 52

d. the fertilization envelope would not form.

Question 53

In humans, identical twins are possible because

a. extraembryonic cells interact with the zygote nucleus.
b. convergent extension occurs.
c. early blastomeres can form a complete embryo if isolated.
d. the gray crescent divides the dorsal-ventral axis into new cells.

Answer 53

c. early blastomeres can form a complete embryo if isolated.

Question 54

Cells transplanted from the neural tube of a frog embryo to the ventral part of another embryo develop into nervous system tissues. This result indicates that the transplanted cells were

a. totipotent.
b. determined.
c. differentiated.
d. mesenchymal.

Answer 54

b. determined.