Question 1

Which of the following is the largest cell involved in frog reproduction?

Accepted Answer

A)  an egg 
B)  a blastomere in the vegetal pole 
C)  a blastomere in the animal pole 
D)  one of the products of the first cleavage

Question 2

Suppose that during gastrulation in humans, a protease (an enzyme that degrades proteins) is present such that the enzymes released by the trophoblast cannot function. What is the most likely immediate outcome of this situation?

Accepted Answer

A)  The embryo will not implant into the endometrium. 
B)  The blastocyst will not form. 
C)  Cleavage will not occur. 
D)  Organogenesis will not occur.

Question 3

Which of the following correctly describes the sequence of developmental milestones in chordates?

Accepted Answer

A)  blastula → gastrula → cleavage 
B)  cleavage → gastrula → blastula 
C)  cleavage → blastula → gastrula 
D)  gastrula → blastula → cleavage

Question 4

The eggs of which of the following organisms contains the least amount of yolk?

Accepted Answer

A)  bird 
B)  frog 
C)  eutherian mammal 
D)  reptile

Question 5

The formation of the fertilization envelope in a sea urchin egg is most directly stimulated by an increase in the cytosolic concentration of which of the following ions?

Accepted Answer

A)  calcium ions 
B)  hydrogen ions 
C)  potassium ions 
D)  sodium ions

Question 6

The migratory neural crest cells give rise to which of the following structures?

Accepted Answer

A)  the brain 
B)  the spinal cord 
C)  a variety of peripheral neural and non-neural structures 
D)  the lining of the lungs and of the digestive tract

Question 7

Which of the following are found in developmental precursors to the gonadal tissues of Caenorhabditis elegans?

Accepted Answer

A)  proteins of maternal origin 
B)  high concentrations of potassium ions 
C)  T tubules for the propagation of action potentials 
D)  P granules of mRNA and protein

Question 8

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. Which of the following processes did the drug most likely influence?

Accepted Answer

A)  early cleavage divisions 
B)  differentiation of bone tissue 
C)  morphogenesis 
D)  gastrulation

Question 9

In which of the following pairs of organisms does holoblastic cleavage typically occur?

Accepted Answer

A)  humans and fish 
B)  sea urchins and birds 
C)  sea urchins and humans 
D)  birds and fish

Question 10

Treating an oocyte with a chemical that binds calcium and magnesium ions will block ________.

Accepted Answer

A)  the acrosomal reaction 
B)  fusion of sperm and egg nuclei 
C)  the fast block to polyspermy 
D)  formation of the fertilization envelope

Question 11

Just prior to the onset of gastrulation in an embryo, the "organizer" cells are specified. What would you expect in the developing embryo if the specification of these cells were experimentally blocked?

Accepted Answer

A)  There would be no effect on development. 
B)  Gastrulation would not occur, and normal development would cease. 
C)  The body axes would develop normally, but the embryo would not grow appendages. 
D)  The embryo would not develop an intestine, but all other organs and tissues would develop normally.

Question 12

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

Accepted Answer

A)  extraembryonic membranes 
B)  yolk 
C)  cleavage 
D)  gastrulation

Question 13

What does the archenteron of the developing sea urchin eventually develop into?

Accepted Answer

A)  blastocoel 
B)  heart and lungs 
C)  digestive tract 
D)  brain and spinal cord

Question 14

The archenteron develops into ________.

Accepted Answer

A)  the mesoderm 
B)  the endoderm 
C)  the placenta 
D)  the lumen of the digestive tract

Question 15

Which of the following were Hans Spemann and colleagues studying when they developed the concept of the "organizer" in amphibian embryos?

Accepted Answer

A)  medial cells between the optic cups 
B)  anterior terminus of the notochord 
C)  lateral margins of the neural tube 
D)  dorsal lip of the blastopore

Question 16

Use the following information to answer the question.
In an investigation into sperm-oocyte binding, researchers isolated the egg receptor protein, ERB1, from the sea urchin Strongylocentrotus purpuratus. ERB1 binds to the sperm acrosomal protein, bindin, during fertilization. The researchers coupled the ERB1 receptor from S. purpuratus to plastic microbeads and then mixed the ERB1-coupled beads with sperm from S. purpuratus or from the related species, S. franciscanus. A summary of the treatment mixtures and a graph of the results are shown.
Treatments:
A: S. purpuratus sperm mixed with S. purpuratus ERB1-coupled beads
B: S. purpuratus sperm mixed with beads with no coupled ERB1 protein
C: S. franciscanus sperm mixed with S. purpuratus ERB1 beads
D: S. franciscanus sperm mixed with beads with no coupled ERB1 protein 
Which of the following conclusions is most consistent with the data?

Accepted Answer

A)  Plastic beads do not bind at all to sperm from either species of sea urchin. 
B)  ERB1 prevents S. franciscanus sperm from binding the beads. 
C)  Sperm from S. purpuratus bind to beads more if ERB1 is present than if ERB1 is not present. 
D)  S. franciscanus and S. purpuratus are the same species.

Question 17

Release of the acrosomal contents during fertilization most directly results in which of the following events?

Accepted Answer

A)  blocking polyspermy 
B)  helping propel more sperm toward the egg 
C)  digesting the protective jelly coat on the surface of the egg 
D)  triggering the completion of meiosis by the sperm

Question 18

Which of the following is a primary external factor in determining the polarity of the body axes in chick embryos?

Accepted Answer

A)  light 
B)  oxygen availability 
C)  gravity 
D)  moisture

Question 19

Which of the following is most likely to occur if an amphibian zygote is manipulated so that the first cleavage plane fails to divide the gray crescent?

Accepted Answer

A)  the daughter cell with the entire gray crescent will die 
B)  both daughter cells will develop normally, because amphibians are totipotent at this stage 
C)  only the daughter cell with the gray crescent will develop normally 
D)  both daughter cells will develop abnormally

Question 20

Which of the following correctly describes gastrulation in frog embryos?

Accepted Answer

A)  causes the ectoderm and endoderm layers to invert 
B)  occurs along the primitive streak in the animal hemisphere 
C)  proceeds by involution as cells roll over the lip of the blastopore 
D)  occurs within the inner cell mass that is embedded in the large amount of yolk

Exam 46: Development in Animals