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

1. A) abnormally high levels of carbonic acid in the cytosol
2. B) abnormally low levels of extracellular oxygen
3. C) injection of calcium ions into the cytosol
4. D) depletion of its ATP supplies

c

2) The formation of the fertilization envelope requires an increase in the cytosolic concentration of ________.

1. A) calcium ions
2. B) hydrogen ions
3. C) potassium ions
4. D) sodium ions

a

3) Contact of a sea urchin egg with signal molecules on sperm causes the egg to undergo a brief ________.

1. A) mitosis
2. B) membrane depolarization
3. C) vitellogenesis
4. D) acrosomal reaction

b

4) The plasma membrane of the sea urchin egg ________.

1. A) is outside of the fertilization membrane
2. B) releases calcium, which initiates the cortical reaction
3. C) has receptor molecules that are specific for binding acrosomal proteins
4. D) is a mesh of proteins crossing through the cytosol of the egg

c

5) Fertilization of an egg without activation is most like ________.

1. A) placing the key in the ignition of a car but not starting the engine
2. B) resting during halftime of a basketball game
3. C) preparing a pie from scratch and baking it in the oven
4. D) walking to the cafeteria and eating lunch

a

6) A reproductive difference between sea urchins and humans is ________.

1. A) the sea urchin egg completes meiosis prior to fertilization, but meiosis in humans is completed after fertilization
2. B) sea urchin eggs and sperm are of equal size, but human eggs are much bigger than human sperm
3. 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
4. D) sea urchin zygotes get their mitochondria from the sperm, but human zygotes get their mitochondria from the egg

a

7) During fertilization, the acrosomal contents ________.

1. A) block polyspermy
2. B) help propel more sperm toward the egg
3. C) digest the protective jelly coat on the surface of the egg
4. D) trigger the completion of meiosis by the sperm

c

8) In a newly fertilized egg, the vitelline layer ________.

1. A) lifts away from the egg and hardens to form a fertilization envelope
2. B) secretes hormones that enhance steroidogenesis by the ovary
3. C) reduces the loss of water from the egg and prevents desiccation
4. D) provides most of the nutrients used by the zygote

a

9) In sea urchins, the "fast block" and the longer lasting "slow block" to polyspermy, respectively, are ________.

1. A) the acrosomal reaction and the formation of egg white
2. B) the cortical reaction and the formation of yolk protein
3. C) the jelly coat of the egg and the vitelline membrane
4. D) membrane depolarization and the cortical reaction

d

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

1. A) acrosomal reaction would be blocked
2. B) fusion of sperm and egg nuclei would be blocked
3. C) fast block to polyspermy would not occur
4. D) fertilization envelope would not be formed

d

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

1. A) fertilization membrane
2. B) egg plasma membrane
3. C) cytosol of the egg
4. D) mitochondria of the egg

b

16) At the moment of sperm penetration, human eggs ________.

1. A) have used flagellar propulsion to move from the ovary to the oviduct
2. B) are still located within the ovary
3. C) have a paper-thin cell of calcium carbonate that prevents desiccation

D) are still surrounded by follicular cells

d

17) Among these choices, the largest cell involved in frog reproduction is ________.

1. A) an egg
2. B) a blastomere in the vegetal pole
3. C) a blastomere in the animal pole

D) one of the products of the first cleavage

a

18) The pattern of embryonic development in which only the cells lacking yolk subsequently undergo cleavage is called ________.

1. A) holoblastic development, which is typical of marsupial mammals
2. B) meroblastic development, which is typical of humans
3. C) holoblastic development, which is typical of amphibians
4. D) meroblastic development, which is typical of birds

d

19) As cleavage continues during frog development, the size of the blastomeres ________.

1. A) increases as the number of the blastomeres decreases
2. B) increases as the number of the blastomeres increases
3. C) decreases as the number of the blastomeres increases
4. D) decreases as the number of the blastomeres decreases

c

20) The vegetal pole of a frog zygote differs from the animal pole in that ________.

1. A) the vegetal pole has a higher concentration of yolk
2. B) the blastomeres originate only in the vegetal pole
3. C) the vegetal pole cells undergo mitosis, but not cytokinesis
4. D) the polar bodies bud from this region

a

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

1. I) sea urchins
2. II) humans

III) birds

1. IV) fish

1. A) both II and IV
2. B) both I and III
3. C) both I and II
4. D) I only

c

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

1. A) blastula → gastrula → cleavage
2. B) cleavage → gastrula → blastula
3. C) cleavage → blastula → gastrula
4. D) gastrula → blastula → cleavage

c

23) The first cavity formed during frog development is the ________.

1. A) blastopore
2. B) mouth
3. C) blastocoel
4. D) anus

c

24) 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?

1. A) The sperm allow morphogenesis to proceed.
2. B) Sperm trigger egg activation.
3. C) Cell differentiation is initiated by the sperm.
4. D) Sperm are necessary to produce a diploid zygote.

b

25) The cortical reaction of sea urchin eggs functions directly in ________.

1. A) the formation of a fertilization envelope
2. B) the production of a fast block to polyspermy
3. C) the release of hydrolytic enzymes from the sperm
4. D) the generation of an electrical impulse by the egg

a

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

1. A) first cell division → synthesis of embryo's DNA begins → acrosomal reaction → cortical reaction
2. B) cortical reaction → synthesis of embryo's DNA begins → acrosomal reaction → first cell division
3. C) cortical reaction → acrosomal reaction → first cell division → synthesis of embryo's DNA begins
4. D) acrosomal reaction → cortical reaction → synthesis of embryo's DNA begins → first cell division

d

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

1. A) an insect
2. B) an amphibian
3. C) a bird
4. D) a sea urchin

c

28) Cells move to new positions as an embryo establishes its three germ tissue layers during ________.

1. A) determination
2. B) cleavage
3. C) induction
4. D) gastrulation

d

29) The outer-to-inner sequence of tissue layers in a post-gastrulation vertebrate embryo is ________.

1. A) endoderm → ectoderm → mesoderm
2. B) mesoderm → endoderm → ectoderm
3. C) ectoderm → mesoderm → endoderm
4. D) ectoderm → endoderm → mesoderm

c

30) If gastrulation was blocked by an environmental toxin, then ________.

1. A) cleavage would not occur in the zygote
2. B) embryonic germ layers would not form
3. C) the blastula would not be formed
4. D) the blastopore would form above the gray crescent in the animal pole

b

31) The archenteron of the developing sea urchin eventually develops into the ________.

1. A) blastocoel
2. B) heart and lungs
3. C) digestive tract
4. D) brain and spinal cord

c

32) In a frog embryo, gastrulation ________.

1. A) produces a blastocoel displaced into the animal hemisphere
2. B) occurs along the primitive streak in the animal hemisphere
3. C) proceeds by involution as cells roll over the lip of the blastopore
4. D) occurs within the inner cell mass that is embedded in the large amount of yolk

c

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

1. A) The mesoderm gives rise to the notochord.
2. B) The endoderm gives rise to the hair follicles.
3. C) The ectoderm gives rise to the liver.
4. D) The mesoderm gives rise to the lungs.

a

34) The primitive streak in a bird is the functional equivalent of ________.

1. A) the lip of the blastopore in the frog
2. B) the archenteron in a frog
3. C) the notochord in a mammal
4. D) neural crest cells in a mammal

a

35) In all vertebrate animals, development requires ________.

1. A) a large supply of yolk
2. B) an aqueous environment
3. C) extraembryonic membranes
4. D) a primitive streak

b

36) The least amount of yolk would be found in the egg of a ________.

1. A) bird
2. B) frog
3. C) eutherian mammal
4. D) reptile

c

37) At the time of implantation, the human embryo is called a ________.

1. A) blastocyst
2. B) gastrula
3. C) fetus
4. D) zygote

a

38) Uterine implantation due to enzymatic digestion of the endometrium is initiated by the ________.

1. A) inner cell mass
2. B) endoderm
3. C) mesoderm
4. D) trophoblast

d

39) 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 ________.

1. A) early cleavage divisions
2. B) differentiation of bone tissue
3. C) morphogenesis
4. D) gastrulation

c

40) The migratory neural crest cells ________.

1. A) form most of the central nervous system
2. B) form the spinal cord in the frog
3. C) form a variety of neural and non-neural structures
4. D) form the lining of the lungs and of the digestive tract

c

41) Which of the following is a result of gastrulation in animals?

1. I) The archenteron is formed.
2. II) The body axes are established.

III) The germ layers are formed.

1. A) I
2. B) III
3. C) I and II
4. D) I, II, and III

d

42) Cell migration occurs extensively during ________.

1. A) organogenesis, but not during gastrulation or cleavage
2. B) cleavage, but not during gastrulation or organogenesis
3. C) gastrulation and cleavage
4. D) both gastrulation and organogenesis

d

43) Changes in the shape of a cell usually involve a reorganization of the ________.

1. A) nucleus
2. B) cytoskeleton
3. C) extracellular matrix
4. D) transport proteins

b

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

1. A) adrenal medulla—endoderm
2. B) nervous system—mesoderm
3. C) kidney—mesoderm
4. D) skin—endoderm and mesoderm

c

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

1. A) notochord
2. B) neural tube
3. C) mesoderm
4. D) archenteron

b

46) During metamorphosis, a tadpole's tail is reduced in size by the process of ________.

1. A) regeneration
2. B) apoptosis
3. C) oxidative phosphorylation
4. D) redifferentiation

b

47) The term applied to a morphogenetic process whereby cells extend themselves, making the mass of the cells narrower and wider, is ________.

1. A) convergent extension
2. B) induction
3. C) invagination
4. D) involution

a

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

1. A) the formation of an embryonic epiblast and hypoblast
2. B) the formation of an embryonic trophoblast
3. C) the formation of an embryonic yolk plug
4. D) the formation of an embryonic gray crescent

a

49) During frog development, the blastocoel ________.

1. A) becomes the archenteron
2. B) gives rise to the endoderm
3. C) gives rise to the placenta
4. D) is replaced by the expanding archenteron

d

50) Which of the following correctly matches the extraembryonic membrane with its function?

1. A) amnion—waste disposal
2. B) chorion—nutrient storage
3. C) allantois—waste storage
4. D) yolk sac—gas exchange

c

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

1. A) provide an aqueous environment for embryo development
2. B) provide nutrients that produce energy for development
3. C) direct morphogenesis within the embryo
4. D) give rise to crucial organ systems, like the heart and brain

a

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

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

c

53) Hans Spemann and colleagues developed the concept of the "organizer" in amphibian embryos while studying the ________.

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

d

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

1. A) chickens, Gallus domesticus
2. B) African clawed frogs, Xenopus laevis
3. C) fruit flies, Drosophila melanogaster
4. D) nematodes, Caenorhabditis elegans

d

Section: 47.3

55) The developmental precursors to the gonadal tissues of Caenorhabditis elegans uniquely contain ________.

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

d

56) One primary factor in shaping the polarity of the body axes in chick embryos is ________.

1. A) light
2. B) membrane potential
3. C) gravity
4. D) moisture

c

57) The arrangement of organs and tissues in their characteristic places in 3-D space defines ________.

1. A) pattern formation
2. B) differentiation
3. C) determination
4. D) organogenesis

a

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

1. A) positional information for limb-bud pattern formation
2. B) guidance signals needed for correct gastrulation
3. C) unequal cytokinesis of blastomeres
4. D) the developmental substrate for the kidneys

a

59) The nematode Caenorhabditis elegans ________.

1. A) is composed of about 1,000 cells, in which the developmental origin of each cell has been mapped
2. B) has only a single chromosome, which has been fully sequenced
3. C) has about 1,000 genes, each of which has been fully sequenced
4. D) uniquely, among animals, utilizes programmed cell death during normal development

a

60) In humans, identical twins are possible because ________.

1. A) cytoplasmic determinants are distributed unevenly in unfertilized eggs
2. B) extraembryonic cells interact with the zygote nucleus
3. C) early blastomeres can form a complete embryo if isolated
4. D) the gray crescent divides the dorsal-ventral axis into new cells

c

61) 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 ________.

1. A) totipotent
2. B) determined
3. C) differentiated
4. D) mesenchymal

b

62) 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?

1. A) The transplanted tissue induced multiple limbs to develop on the ventral side of the recipient embryo.
2. B) The transplanted tissue inhibited normal cell division on the dorsal side of the recipient embryo that lead to its death.
3. C) The transplanted tissue had no effect on either the ventral or dorsal side of the recipient embryo so it continued to develop normally.
4. D) The transplanted tissue induced the formation of a second notochord and neural tube on the ventral side of the developing embryo.

d

63) 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?

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

b