Chapter 47

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1

1) Even in the absence of sperm, metabolic activity in an egg can be artificially activated by _____.
A) abnormally high levels of carbonic acid in the cytosol
B) abnormally low levels of extracellular oxygen

C) injection of calcium ions into the cytosol
D) depletion of its ATP supplies

Answer: C

2

2) The formation of the fertilization envelope requires an increase in the availability of _____. A) calcium ions
B) hydrogen ions
C) potassium ions

D) sodium ions

Answer: A

3

3) Contact of a sea urchin egg with signal molecules on sperm causes the egg to undergo a brief _____.
A) mitosis
B) membrane depolarization

C) vitellogenesis
D) acrosomal reaction

Answer: B

4

4) The plasma membrane of the sea urchin egg _____.
A) is outside of the fertilization membrane
B) releases calcium, which initiates the cortical reaction
C) has receptor molecules that are specific for binding acrosomal proteins

D) is a mesh of proteins crossing through the cytosol of the egg

Answer: C

5

5) 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) preparing a pie from scratch and baking it in the oven
D) walking to the cafeteria and eating lunch

Answer: A

6

6) A reproductive difference between sea urchins and humans is _____.
A) the sea urchin egg completes meiosis prior to fertilization, but meiosis in humans is completed after fertilization
B) sea urchin eggs and sperm are of equal size, but human eggs are much bigger than human sperm
C) sea urchins, but not humans, have a need to block polyspermy, because only in sea urchins can there be more than one source of sperm to fertilize the eggs
D) sea urchin zygotes get their mitochondria from the sperm, but human zygotes get their mitochondria from the egg

Answer: A

7

7) During fertilization, the acrosomal contents _____.
A) block polyspermy
B) help propel more sperm toward the egg
C) digest the protective jelly coat on the surface of the egg

D) trigger the completion of meiosis by the sperm

Answer: C

8

8) In a newly fertilized egg, the vitelline layer _____.
A) lifts away from the egg and hardens to form a fertilization envelope

B) secretes hormones that enhance steroidogenesis by the ovary
C) reduces the loss of water from the egg and prevents desiccation
D) provides most of the nutrients used by the zygote

Answer: A

9

9) In sea urchins, the "fast block" and the longer lasting "slow block" to polyspermy, respectively, are _____.
A) the acrosomal reaction and the formation of egg white
B) the cortical reaction and the formation of yolk protein

C) the jelly coat of the egg and the vitelline membrane

D) membrane depolarization and the cortical reaction

Answer: D

10

10) In an egg cell treated with a chemical that binds calcium and magnesium ions, the _____. A) acrosomal reaction would be blocked
B) fusion of sperm and egg nuclei would be blocked
C) fast block to polyspermy would not occur

D) fertilization envelope would not be formed

Answer: D

11

11) In mammalian eggs, the receptors for sperm are found in the _____.

A) fertilization membrane
B) egg plasma membrane
C) cytosol of the egg

D) mitochondria of the egg

Answer: B

12

12) A human blastomere is _____.
A) an embryonic cell that is smaller than the ovum
B) an embryonic structure that includes a fluid-filled cavity

C) that part of the acrosome that opens the egg's membrane

D) a cell that contains a (degenerating) second polar body

Answer: A

13

13) At the moment of sperm penetration, human eggs _____.
A) have used flagellar propulsion to move from the ovary to the oviduct

B) are still located within the ovary
C) have a paper-thin cell of calcium carbonate that prevents desiccation

D) are still surrounded by follicular cells

Answer: D

14

14) In a developing frog embryo, most of the yolk is _____.

A) located near the animal pole
B) located near the vegetal pole
C) found within the cleavage furrow

D) distributed equally throughout the embryo

Answer: B

15

15) Among these choices, the largest cell involved in frog reproduction is _____.

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

Answer: A

16

16) The pattern of embryonic development in which only the cells lacking yolk subsequently undergo cleavage is called _____.
A) holoblastic development, which is typical of marsupial mammals
B) meroblastic development, which is typical of humans

C) holoblastic development, which is typical of amphibians

D) meroblastic development, which is typical of birds

Answer: D

17

17) As cleavage continues during frog development, the size of the blastomeres _____. A) increases as the number of the blastomeres decreases
B) increases as the number of the blastomeres increases
C) decreases as the number of the blastomeres increases

D) decreases as the number of the blastomeres decreases

Answer: C

18

18) The vegetal pole of a frog zygote differs from the animal pole in that _____.

A) the vegetal pole has a higher concentration of yolk
B) the blastomeres originate only in the vegetal pole
C) the vegetal pole cells undergo mitosis, but not cytokinesis

D) the polar bodies bud from this region

Answer: A

19

19) Meroblastic cleavage occurs in _____.
A) sea urchins, but not in humans or birds
B) humans, but not in sea urchins or birds
C) birds, but not in sea urchins or humans
D) both sea urchins and birds, but not in humans

Answer: C

20

20) Which of the following correctly displays the sequence of developmental milestones?

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

D) gastrula → blastula → cleavage

Answer: C

21

21) The first cavity formed during frog development is the _____.

A) blastopore
B) mouth
C) blastocoel

D) anus

Answer: C

22

22) 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. In this case, the sperm appear to be used only for _____.

A) morphogenesis
B) egg activation
C) cell differentiation
D) the creation of a diploid cell

Answer: B

23

23) 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

Answer: A

24

24) The structure of the Drosophila gene, called Tinman, is similar to a gene in humans that also _____.
A) promotes ear development
B) specifies the location of the heart

C) determines structures in the eyes
D) specifies limb elongation points

Answer: B

25

25) From earliest to latest, the overall sequence of early development proceeds in which of the following sequences?
A) first cell division → synthesis of embryo's DNA begins → acrosomal reaction → cortical reaction

B) cortical reaction → synthesis of embryo's DNA begins → acrosomal reaction → first cell division
C) cortical reaction → acrosomal reaction → first cell division → synthesis of embryo's DNA begins

D) acrosomal reaction → cortical reaction → synthesis of embryo's DNA begins → first cell division

Answer: D

26

26) An embryo with meroblastic cleavage, extraembryonic membranes, and a primitive streak must be that of _____.
A) an insect
B) an amphibian

C) a bird
D) a sea urchin

Answer: C

27

27) Cells move to new positions as an embryo establishes its three germ-tissue layers during _____.
A) determination
B) cleavage

C) induction
D) gastrulation

Answer: D

28

28) The outer-to-inner sequence of tissue layers in a post-gastrulation vertebrate embryo is _____.
A) endoderm → ectoderm → mesoderm
B) mesoderm → endoderm → ectoderm

C) ectoderm → mesoderm → endoderm
D) ectoderm → endoderm → mesoderm

Answer: C

29

29) If gastrulation was blocked by an environmental toxin, then _____.

A) cleavage would not occur in the zygote
B) embryonic germ layers would not form
C) the blastula would not be formed

D) the blastopore would form above the gray crescent in the animal pole

Answer: B

30

30) The archenteron of the developing sea urchin eventually develops into the _____.

A) blastocoel
B) heart and lungs
C) digestive tract

D) brain and spinal cord

Answer: C

31

31) In a frog embryo, gastrulation _____.
A) produces a blastocoel displaced into the animal hemisphere
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

Answer: C

32

32) Which of the following is a correct description of the fate of the germ layers?

A) The mesoderm gives rise to the notochord.
B) The endoderm gives rise to the hair follicles.
C) The ectoderm gives rise to the liver.

D) The mesoderm gives rise to the lungs.

Answer: A

33

33) The primitive streak in a bird is the functional equivalent of _____.

A) the lip of the blastopore in the frog
B) the archenteron in a frog
C) the notochord in a mammal

D) neural crest cells in a mammal

Answer: A

34

34) In all vertebrate animals, development requires _____.

A) a large supply of yolk
B) an aqueous environment
C) extraembryonic membranes

D) a primitive streak

Answer: B

35

35) The least amount of yolk would be found in the egg of a _____.

A) bird
B) frog
C) eutherian mammal

D) reptile

Answer: C

36

36) At the time of implantation, the human embryo is called a _____.

A) blastocyst
B) gastrula
C) fetus

D) zygote

Answer: A

37

37) Uterine implantation due to enzymatic digestion of the endometrium is initiated by the _____.
A) inner cell mass
B) endoderm

C) mesoderm
D) trophoblast

Answer: D

38

38) Thalidomide, now banned for use as a sedative in 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 arm and leg deformities, suggesting that the drug most likely influenced _____.
A) early cleavage divisions

B) differentiation of bone tissue

C) morphogenesis
D) organogenesis

Answer: C

39

39) The migratory neural crest cells _____.
A) form most of the central nervous system
B) form the spinal cord in the frog
C) form a variety of neural and non-neural structures

D) form the lining of the lungs and of the digestive tract

Answer: C

40

40) From earliest to latest, the overall sequence of early development proceeds in which of the following sequences?
A) gastrulation → organogenesis → cleavage
B) cleavage → gastrulation → organogenesis

C) gastrulation → blastulation → neurulation
D) preformation → morphogenesis → neurulation

Answer: B

41

41) Changes in cell position occur extensively during _____.

A) organogenesis, but not during gastrulation or cleavage
B) cleavage, but not during gastrulation or organogenesis
C) gastrulation and cleavage

D) gastrulation

Answer: D

42

42) Changes in the shape of a cell usually involve a reorganization of the _____.

A) nucleus
B) cytoskeleton
C) extracellular matrix

D) transport proteins

Answer: B

43

43) When we compare animal development to plant development, we find that _____.

A) plant cells, but not animal cells, migrate during morphogenesis
B) animal cells, but not plant cells, migrate during morphogenesis
C) plant cells and animal cells migrate extensively during morphogenesis

D) neither plant cells nor animal cells migrate during morphogenesis

Answer: B

44

44) Select the choice that correctly associates the organ with its embryonic sources.

A) anterior pituitary gland — mesoderm and endoderm
B) thyroid gland — mesoderm and ectoderm
C) adrenal gland — ectoderm and mesoderm

D) skin — endoderm and mesoderm

Answer: C

45

45) The embryonic precursor to the human spinal cord is the _____.

A) notochord
B) neural tube
C) mesoderm

D) archenteron

Answer: B

46

46) During metamorphosis, a tadpoles tail is reduced in size by the process of _____.

A) regeneration
B) apoptosis
C) oxidative phosphorylation

D) re-differentiation

Answer: B

47

47) The term applied to a morphogenetic process whereby cells extend themselves, making the mass of the cells narrower and wider, is _____.
A) convergent extension
B) induction

C) elongational streaming
D) bi-axial elongation

Answer: A

48

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

A) the formation of an embryonic epiblast and hypoblast
B) the formation of an embryonic trophoblast
C) the formation of an embryonic yolk plug

D) the formation of an embryonic gray crescent

Answer: A

49

49) The archenteron of a frog develops into the _____.

A) blastocoel
B) endoderm
C) placenta

D) lumen of the digestive tract

Answer: D

50

50) What structural adaptation in chickens allows them to lay their eggs in arid environments rather than in water?
A) amnion
B) yolk

C) gastrulation
D) development of the brain from ectoderm

Answer: A

51

51) If an amphibian zygote is manipulated so that the first cleavage plane fails to divide the gray crescent, then _____.
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

Answer: C

52

52) Hans Spemann and colleagues developed the concept of the organizer in amphibian embryos while studying the _____.
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

Answer: D

53

53) Which of the following is an adult organism that has fewer than 1,000 cells?

A) chickens, Gallus domesticus
B) African clawed frogs, Xenopus laevis
C) fruit flies, Drosophila melanogaster

D) nematodes, Caenorhabditis elegans

Answer: D

54

54) The developmental precursors to the gonadal tissues of Caenorhabditis elegans uniquely contain _____.
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

Answer: D

55

55) Two primary factors in shaping the polarity of the body axes in chick embryos are _____.

A) light and temperature
B) salt gradients and membrane potentials
C) gravity and pH

D) moisture and mucus

Answer: C

56

56) The arrangement of organs and tissues in their characteristic places in 3-D space defines _____.
A) pattern formation
B) differentiation

C) determination
D) organogenesis

Answer: A

57

57) If the apical ectodermal ridge is surgically removed from an embryo, it will lose _____.

A) positional information for limb-bud pattern formation
B) guidance signals needed for correct gastrulation
C) unequal cytokinesis of blastomeres

D) the developmental substrate for the kidneys

Answer: A

58

58) The nematode Caenorhabditis elegans _____.
A) is composed of about 1000 cells, in which the developmental origin of each cell has been mapped
B) has only a single chromosome, which has been fully sequenced
C) has about 1000 genes, each of which has been fully sequenced
D) uniquely, among animals, utilizes programmed cell death during normal development

Answer: A

59

59) In humans, identical twins are possible because _____.
A) cytoplasmic determinants are distributed unevenly in unfertilized eggs

B) extraembryonic cells interact with the zygote nucleus
C) early blastomeres can form a complete embryo if isolated
D) the gray crescent divides the dorsal-ventral axis into new cells

Answer: C

60

60) 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: B

61

61) Embryonic induction, the influence of one group of cells on another group of cells, plays a critical role in embryonic development. In 1924, Hans Spemann and Hilde Mangold transplanted a piece of tissue that influences the formation of the notochord and neural tube, from the dorsal lip of an amphibian embryo to the ventral side of another amphibian embryo. If embryonic induction occurred, which of the following observations justifies the claim of embryonic induction?
A) The transplanted tissue induced multiple limbs to develop on the ventral side of the recipient embryo.
B) The transplanted tissue inhibited normal cell division on the dorsal side of the recipient embryo that lead to its death.
C) The transplanted tissue had no effect on either the ventral or dorsal side of the recipient embryo so it continued to develop normally.
D) The transplanted tissue induced the formation of a second notochord and neural tube on the ventral side of the developing embryo.

Answer: D