During the early part of the cleavage stage in frog development, the rapidly developing cells

During the early part of the cleavage stage in frog development, the rapidly developing cells 

A) skip the mitosis phase of the cell cycle.
B) skip the S phase of the cell cycle.
C) skip the G1 and G2 phases of the cell cycle.
D) rapidly increase the volume and mass of the embryo.
E) skip the cytokinesis phase of the cell cycle.





Answer: C

As cleavage continues during frog development, the size of the blastomeres

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.
E) increases as the number of the blastomeres stays the same.






Answer: C

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

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

A) arcadian development, which is typical of insects.
B) holoblastic development, which is typical of marsupial mammals.
C) meroblastic development, which is typical of humans.
D) holoblastic development, which is typical of amphibians.
E) meroblastic development, which is typical of birds.






Answer: E

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

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

A) the spermatozoon.
B) the ovum.
C) a blastomere in the vegetal pole.
D) a blastomere in the animal pole.
E) one of the products of the first cleavage.






Answer: B

In a developing frog embryo, most of the yolk is

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) found within the blastocoels.
E) distributed equally throughout the embryo.







Answer: B

At the moment of sperm penetration, human eggs

At the moment of sperm penetration, human eggs 

A) have used flagellar propulsion to move from the ovary to the oviduct.
B) accept as many sperm as possible in order to select the one with the highest fertility.
C) are still located within the ovary.
D) have a paper-thin cell of calcium carbonate that prevents desiccation.
E) are still surrounded by follicular cells.






Answer: E

A human blastomere is

A human blastomere is 

A) an embryonic cell that is much 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 component of the zona pellucida.
E) a cell that contains a (degenerating) second polar body.





Answer: A

Compared to sea urchin eggs, those of mammals

Compared to sea urchin eggs, those of mammals 

A) complete the fertilization process more rapidly.
B) have not already completed meiosis at the time of ovulation.
C) have a more distinct animal pole.
D) have a more distinct vegetal pole.
E) have no requirement for the cortical reaction.






Answer: B

In mammalian eggs, the receptors for sperm are found in the

In mammalian eggs, the receptors for sperm are found in the 

A) fertilization membrane.
B) zona pellucida.
C) cytosol of the egg.
D) nucleus of the egg.
E) mitochondria of the egg.







Answer: B

Fertilization normally

Fertilization normally 

A) reinstates diploidy.
B) follows gastrulation.
C) is required for parthenogenesis.
D) merges two diploid cells into one haploid cell.
E) precedes ovulation.






Answer: A

In mammals, the nuclei resulting from the union of the sperm and the egg are first truly diploid at the end of the

In mammals, the nuclei resulting from the union of the sperm and the egg are first truly diploid at the end of the 

A) acrosomal reaction.
B) completion of spermatogenesis.
C) initial cleavage.
D) activation of the egg.
E) completion of gastrulation.






Answer: C

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

In an egg cell treated with EDTA, 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.
E) zygote would not contain maternal and paternal chromosomes.







Answer: D

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

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.
E) inactivation of the sperm acrosome.







Answer: D

The cortical reaction functions directly in the

The cortical reaction functions directly in the 

A) formation of a fertilization envelope.
B) production of a fast block to polyspermy.
C) release of hydrolytic enzymes from the sperm cell.
D) generation of a nerve-like impulse by the egg cell.
E) fusion of egg and sperm nuclei.







Answer: A

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

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) first cell division ? synthesis of embryo's DNA begins ? acrosomal reaction ? cortical reaction
E) acrosomal reaction ? cortical reaction ? synthesis of embryo's DNA begins ? first cell division





Answer: E

In a newly fertilized egg, the vitelline layer

In a newly fertilized egg, the vitelline layer 

A) opens the egg's nuclear membrane to allow haploid sperm DNA to enter.
B) hardens to form a protective cover.
C) secretes hormones that enhance steroidogenesis by the ovary.
D) reduces the loss of water from the egg and prevents desiccation.
E) provides most of the nutrients used by the zygote.







Answer: B

The vitelline layer of the sea urchin egg

The vitelline layer 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 first visible only when organogenesis is nearly completed.
E) is a mesh of proteins crossing through the cytosol of the egg.






Answer: C

During fertilization, the acrosomal contents

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) nourish the mitochondria of the sperm.
E) trigger the completion of meiosis by the sperm.







Answer: C

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

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

A) mitosis.
B) membrane depolarization.
C) apoptosis.
D) vitellogenesis.
E) acrosomal reaction.





Answer: B

A reproductive difference between sea urchins and humans is

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 are produced by meiosis, but human eggs are produced by mitosis.
C) sea urchin eggs and sperm are of equal size, but human eggs are much bigger than human sperm.
D) 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.
E) sea urchin zygotes get their mitochondria from the sperm but human zygotes get their mitochondria from the egg.






Answer: A

A human zygote undergoes its first cell division

A human zygote undergoes its first cell division 

A) 5 seconds after fertilization.
B) 30 minutes after fertilization.
C) 90 minutes after fertilization.
D) 4 hours after fertilization.
E) 24 hours after fertilization.







Answer: E

A sea urchin zygote undergoes its first cell division

A sea urchin zygote undergoes its first cell division 

A) 5 seconds after fertilization.
B) 30 minutes after fertilization.
C) 90 minutes after fertilization.
D) 4 hours after fertilization.
E) 24 hours after fertilization.







Answer: C

The formation of the fertilization membrane requires an increase in the availability of

The formation of the fertilization membrane requires an increase in the availability of 

A) bicarbonate ions.
B) calcium ions.
C) hydrogen ions.
D) potassium ions.
E) sodium ions.






Answer: B

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

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) exposure to the low pH of the uterus.
E) depletion of its ATP supplies.







Answer: C

Contact of a sperm with signal molecules in the coat of an egg causes the sperm to undergo

Contact of a sperm with signal molecules in the coat of an egg causes the sperm to undergo 

A) mitosis.
B) depolarization.
C) apoptosis.
D) vitellogenesis.
E) the acrosomal reaction.






Answer: E

Fertilization of an egg without activation is most like

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.
E) dropping a rock off a cliff and watching it land in the valley below.






Answer: A

As an embryo develops, new cells are produced as the result of

As an embryo develops, new cells are produced as the result of 

A) differentiation.
B) preformation.
C) cell division.
D) morphogenesis.
E) epigenesis.






Answer: C

The structure of the Drosophila gene called Tinman is similar to a gene in humans that also

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.
E) filters lymphatic fluid.





Answer: B

Which statement about human reproduction is false?

Which statement about human reproduction is false? 

A) Fertilization occurs in the oviduct.
B) Effective hormonal contraceptives are currently available only for females.
C) An oocyte completes meiosis after a sperm penetrates it.
D) The earliest stages of spermatogenesis occur closest to the lumen of the seminiferous tubules.
E) Spermatogenesis and oogenesis require different temperatures.





Answer: D

For which of the following is the number the same in spermatogenesis and oogenesis?

For which of the following is the number the same in spermatogenesis and oogenesis? 

A) interruptions in meiotic divisions
B) functional gametes produced by meiosis
C) meiotic divisions required to produce each gamete
D) gametes produced in a given time period
E) different cell types produced by meiosis






Answer: C

Which of the following is a true statement?

Which of the following is a true statement? 

A) All mammals have menstrual cycles.
B) The endometrial lining is shed in menstrual cycles but reabsorbed in estrous cycles.
C) Estrous cycles are more frequent than menstrual cycles.
D) Estrous cycles are not controlled by hormones.
E) Ovulation occurs before the endometrium thickens in estrous cycles.






Answer: B

During human gestation, rudiments of all organs develop

During human gestation, rudiments of all organs develop 

A) in the first trimester.
B) in the second trimester.
C) in the third trimester.
D) while the embryo is in the oviduct.
E) during the blastocyst stage.





Answer: A

Peaks of LH and FSH production occur during

Peaks of LH and FSH production occur during 

A) the menstrual flow phase of the uterine cycle.
B) the beginning of the follicular phase of the ovarian cycle.
C) the period just before ovulation.
D) the end of the luteal phase of the ovarian cycle.
E) the secretory phase of the menstrual cycle.






Answer: C

Which of the following is not properly paired?

Which of the following is not properly paired? 

A) seminiferous tubule?cervix
B) Sertoli cells?follicle cells
C) testosterone?estradiol
D) scrotum?labia majora
E) vas deferens?oviduct







Answer: A

In male mammals, excretory and reproductive systems share

In male mammals, excretory and reproductive systems share 

A) the testes.
B) the urethra.
C) the seminal vesicle.
D) the vas deferens.
E) the prostate.






Answer: B

Which of the following characterizes parthenogenesis?

Which of the following characterizes parthenogenesis? 

A) An individual may change its sex during its lifetime.
B) Specialized groups of cells grow into new individuals.
C) An organism is first a male and then a female.
D) An egg develops without being fertilized.
E) Both mates have male and female reproductive organs.




Answer: D

Imagine that a woman is in the final week of her pregnancy. Her doctor gives her an injection of oxytocin. The likely result of this is that the pregnant woman would

Imagine that a woman is in the final week of her pregnancy. Her doctor gives her an injection of oxytocin. The likely result of this is that the pregnant woman would 

A) undergo the loss of oxytocin receptors from her uterine smooth muscle cells.
B) stop secreting prostaglandins from the placenta.
C) undergo vigorous contractions of her uterine muscles.
D) increase the synthesis and secretion of progesterone.
E) be prevented from lactation.






Answer: C

You observe vertebrate organisms with parthenogenetic reproduction, internal development of embryos, and the lack of parental care for its young. Based on this information, you should categorize these organisms as

You observe vertebrate organisms with parthenogenetic reproduction, internal development of embryos, and the lack of parental care for its young. Based on this information, you should categorize these organisms as 

A) earthworms.
B) lizards.
C) birds.
D) frogs.
E) mammals.






Answer: B

So-called "combination" birth control pills function in contraception by

So-called "combination" birth control pills function in contraception by 

A) inhibiting the release of GnRH, FSH, and LH.
B) irritating the uterine lining so as to prevent implantation.
C) causing spontaneous abortions.
D) blocking progesterone receptors, so that pregnancy cannot be maintained.
E) binding to and inactivating any sperm that enter the oviduct.







Answer: A

For lactation to take place, the synthesis of breast milk and its release from the mammary gland, respectively, are caused by

For lactation to take place, the synthesis of breast milk and its release from the mammary gland, respectively, are caused by 

A) testosterone and dihydrotestosterone.
B) estrogen and progesterone.
C) cortisol and testosterone.
D) prolactin and oxytocin.
E) luteinizing hormone and follicle-stimulating hormone.






Answer: D

Time-release progesterone implants function in contraception by

Time-release progesterone implants function in contraception by 

A) increasing the frequency of ovulation.
B) thickening the cervical and uterine mucus to impair sperm movement.
C) increasing gonadotropin secretion to abnormally high levels.
D) reducing libido.
E) activating inflammation responses in the uterus.






Answer: B

A vasectomy

A vasectomy 

A) eliminates spermatogenesis.
B) eliminates testosterone synthesis.
C) prevents implantation of an embryo.
D) prevents sperm from exiting the male urethra.
E) prevents oocytes from entering the uterus.





Answer: D

Tubal ligation

Tubal ligation 

A) reduces the incidence of ovulation.
B) prevents fertilization by preventing sperm from entering the uterus.
C) prevents implantation of an embryo.
D) prevents sperm from exiting the male urethra.
E) prevents oocytes from entering the uterus.






Answer: E

Two contraceptive methods that are generally irreversible and which block the gametes from moving to a site where fertilization can occur are

Two contraceptive methods that are generally irreversible and which block the gametes from moving to a site where fertilization can occur are 

A) the male condom and female condom.
B) the male condom and oral contraceptives.
C) vasectomy and tubal ligation.
D) coitus interruptus and rhythm method.
E) the diaphragm and subcutaneous progesterone implant.






Answer: C

The use of birth control pills (oral contraceptives)

The use of birth control pills (oral contraceptives) 

A) reduces the incidence of ovulation.
B) prevents fertilization by keeping the sperm and egg physically separated by a mechanical barrier.
C) prevents implantation of an embryo.
D) prevents sperm from exiting the male urethra.
E) prevents oocytes from entering the uterus.







Answer: A

Among these contraception methods, the highest risk of accidental pregnancy accompanies

Among these contraception methods, the highest risk of accidental pregnancy accompanies 

A) the use of a diaphragm.
B) the use of a condom.
C) the practice of coitus interruptus.
D) a verified vasectomy.
E) the practice of the "rhythm method."






Answer: C

The "immunotolerance" of a pregnant woman toward her unborn child is the result of

The "immunotolerance" of a pregnant woman toward her unborn child is the result of 

A) the tenacity with which the unborn child's immune system counteracts the woman's immune system.
B) the relative quiescence of a pregnant woman's immune system compared to when she was not pregnant.
C) the complete physical separation of her cells from those of the unborn child.
D) the unborn child having enough of the woman's identity so as to escape detection as foreign.
E) modern medical intervention during every pregnancy.






Answer: B

In excreted urine, a reliable "marker" that a pregnancy has initiated is

In excreted urine, a reliable "marker" that a pregnancy has initiated is

A) progesterone.
B) estrogen.
C) follicle-stimulating hormone.
D) chorionic gonadotropin.
E) hypothalamic-releasing hormones.






Answer: D

The thin layer of the developing embryo which secretes a hormone that keeps the corpus luteum functioning is the

The thin layer of the developing embryo which secretes a hormone that keeps the corpus luteum functioning is the 

A) cervix.
B) endometrium.
C) amnion.
D) plasma membrane.
E) chorion.






Answer: E