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Chapter 47

front 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	back 1 Answer: C
front 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	back 2 Answer: A
front 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	back 3 Answer: B
front 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	back 4 Answer: C

front 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	back 5 Answer: A
front 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	back 6 Answer: A
front 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	back 7 Answer: C
front 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	back 8 Answer: A

front 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	back 9 Answer: D
front 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	back 10 Answer: D
front 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	back 11 Answer: B
front 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	back 12 Answer: A

front 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	back 13 Answer: D
front 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	back 14 Answer: B
front 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	back 15 Answer: A
front 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	back 16 Answer: D

front 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	back 17 Answer: C
front 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	back 18 Answer: A
front 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	back 19 Answer: C
front 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	back 20 Answer: C

front 21 21) The first cavity formed during frog development is the _____. A) blastopore B) mouth C) blastocoel D) anus	back 21 Answer: C
front 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	back 22 Answer: B
front 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	back 23 Answer: A
front 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	back 24 Answer: B

front 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	back 25 Answer: D
front 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	back 26 Answer: C
front 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	back 27 Answer: D
front 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	back 28 Answer: C

front 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	back 29 Answer: B
front 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	back 30 Answer: C
front 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	back 31 Answer: C
front 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.	back 32 Answer: A

front 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	back 33 Answer: A
front 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	back 34 Answer: B
front 35 35) The least amount of yolk would be found in the egg of a _____. A) bird B) frog C) eutherian mammal D) reptile	back 35 Answer: C
front 36 36) At the time of implantation, the human embryo is called a _____. A) blastocyst B) gastrula C) fetus D) zygote	back 36 Answer: A

front 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	back 37 Answer: D
front 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	back 38 Answer: C
front 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	back 39 Answer: C
front 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	back 40 Answer: B

front 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	back 41 Answer: D
front 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	back 42 Answer: B
front 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	back 43 Answer: B
front 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	back 44 Answer: C

front 45 45) The embryonic precursor to the human spinal cord is the _____. A) notochord B) neural tube C) mesoderm D) archenteron	back 45 Answer: B
front 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	back 46 Answer: B
front 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	back 47 Answer: A
front 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	back 48 Answer: A

front 49 49) The archenteron of a frog develops into the _____. A) blastocoel B) endoderm C) placenta D) lumen of the digestive tract	back 49 Answer: D
front 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	back 50 Answer: A
front 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	back 51 Answer: C
front 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	back 52 Answer: D

front 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	back 53 Answer: D
front 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	back 54 Answer: D
front 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	back 55 Answer: C
front 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	back 56 Answer: A

front 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	back 57 Answer: A
front 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	back 58 Answer: A
front 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	back 59 Answer: C
front 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	back 60 Answer: B

front 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.

back 61

Answer: D

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Chapter 47