Biology I: Ch. 27
This graph plots the rise and fall of pituitary and ovarian hormones during the human ovarian cycle. Identify each hormone (A-D) and the reproductive events with which each one is associated (P-S). For A-D, choose from estrogen, LH, FSH, and progesterone. For P-S, choose from ovulation, growth of follicle, menstruation, and development of corpus luteum. How would the right-hand side of this graph be altered if pregnancy occurred? What other hormone is responsible for triggering this change?
A. FSH B. estrogen C. LH D. progesterone P. menstruation Q. growth of follicle R. ovulation S. development of corpus luteum If pregnancy occurs, the embryo produces human chorionic gonadotropin (hCG), which maintains the corpus luteum, keeping levels of estrogen and progesterone high.
__________ is the creation of genetically identical offspring by a lone parent.
Asexual reproduction
Many people with XY chromosomes and androgen insensitivity syndrome (AIS), like Katie, are not diagnosed until later in life, rather than at birth. Why is that? Everyday Biology: Male, Female, or Intersex?http://mediaplayer.pearsoncmg.com/assets/xgK_ePZ0XNQ5moIP_NgBpgzfTyZM5hNJ
Babies with XY chromosomes and AIS usually appear to be normal females at birth. It is not until they have a hernia, or fail to menstruate, before a doctor would investigate further.
Compare sperm formation with egg formation. In what ways are the processes similar? In what ways are they different?
Both produce haploid gametes. Spermatogenesis produces four small sperm; oogenesis produces one large egg. In humans, the ovary contains all the primary oocytes at birth, while testes can keep making primary spermatocytes throughout life. Oogenesis is not complete until fertilization, but sperm mature without eggs.
__________ is the splitting off of new individuals from outgrowths of existing ones.
Budding
The levels of pituitary hormones never increase above 10 grams/L of blood.
Cannot be determined from the graph
Which of the following birth control methods also provides the best protection against STDs? - withdrawal - tubal ligation or vasectomy - oral contraceptives - condoms Hint 1. Body fluids cannot be exchanged if the spread of STDs is to be prevented.
Condoms are even more effective against STDs if used with a spermicide.
Which of the following processes, if any, occurs during cleavage? Hint 1. This stage of development is characterized by a rapid increase in cell number.
DNA replication This occurs during cleavage. The embryonic cells are dividing rapidly by mitosis and cytokinesis and, therefore, must be rapidly replicating their DNA.
Which of the following biologically describes a hermaphrodite? Everyday Biology: Male, Female, or Intersex?http://mediaplayer.pearsoncmg.com/assets/xgK_ePZ0XNQ5moIP_NgBpgzfTyZM5hNJ
Earthworms can fertilize each other to produce offspring.
TRUE or FALSE: When comparing oogenesis and spermatogenesis, follicle-stimulating hormone promotes only egg, not sperm, development.
FALSE
TRUE or FALSE: When comparing oogenesis and spermatogenesis, luteinizing hormone triggers ovulation in females and has no other role in reproduction.
FALSE
TRUE or FALSE: When comparing oogenesis and spermatogenesis, primary oocytes and primary spermatocytes follow a similar pattern of development through meiosis.
FALSE
TRUE or FALSE: A function of oxytocin: Oxytocin maintains the corpus luteum during pregnancy
FALSE A function of oxytocin is that it stimulates powerful contractions of smooth muscles in the wall of the uterus.
TRUE or FALSE: A function of oxytocin: Oxytocin stimulates the urinary tract to make prostaglandins.
FALSE A function of oxytocin is that it stimulates powerful contractions of smooth muscles in the wall of the uterus.
TRUE or FALSE: A function of oxytocin: Oxytocin stops the secretion of milk.
FALSE A function of oxytocin is that it stimulates powerful contractions of smooth muscles in the wall of the uterus.
TRUE or FALSE: Genital warts are caused by a bacterium.
FALSE A virus causes genital warts.
TRUE or FALSE: Only about 2% of couples are unable to conceive after one year of trying to get pregnant.
FALSE About 15% of couples are unable to conceive after one year of trying to get pregnant.
TRUE or FALSE: In relation to gametogenesis in humans, sexually mature adults, spermatogenesis and oogenesis produce about the same number of gametes each day.
FALSE Correct: Women produce about one secondary oocyte a month. Men produce millions of sperm each day.
TRUE or FALSE: Fertilization occurs during cleavage.
FALSE DNA replication occurs during cleavage. Cleavage is a stage of development characterized by a rapid increase in cell number.
TRUE or FALSE: Gene transcription occurs during cleavage.
FALSE DNA replication occurs during cleavage. Cleavage is a stage of development characterized by a rapid increase in cell number.
TRUE or FALSE: Meiosis occurs during cleavage?
FALSE DNA replication occurs during cleavage. Cleavage is a stage of development characterized by a rapid increase in cell number.
TRUE or FALSE: The trophoblast cells will form the baby.
FALSE Only cells of the inner cell mass form the baby.
TRUE or FALSE: Extraembryonic membrane and its function: The yolk sac provides a developing human embryo with nourishment.
FALSE This is true of chicks, but in humans the yolk sac produces the embryo's first blood and germ cells.
Which of the following is a disadvantage of asexual reproduction? Hint 1. The offspring of asexually reproducing organisms have the same genetic composition.
It does not increase genetic variability. This is an advantage that sexual reproduction has over asexual reproduction.
What is the function of the thickened endometrium?
It nourishes the early embryo during the process of implantation.
Which of the following most accurately describes Katie's situation? Everyday Biology: Male, Female, or Intersex?http://mediaplayer.pearsoncmg.com/assets/xgK_ePZ0XNQ5moIP_NgBpgzfTyZM5hNJ
Katie was born with testes, but her cells did not respond to the testosterone those testes produced.
A surge in which hormone(s) immediately precedes ovulation?
LH and FSH
What is likely to happen if the placenta of a young human embryo prematurely stopped releasing HCG? Hint 1. HCG stimulates the corpus luteum to continue to secrete progesterone and estrogen.
The embryo might be aborted. The drop in HCG might cause a drop in progesterone and estrogen secretion by the corpus luteum, leading to menstruation and a spontaneous abortion.
The embryos of reptiles (including birds) and mammals have systems of extraembryonic membranes. What are the functions of these membranes, and how do fish and frog embryos survive without them?
The extraembryonic membranes provide a moist environment for the embryos of terrestrial vertebrates and enable the embryos to absorb food and oxygen and dispose of wastes. Such membranes are not needed when an embryo is surrounded by water, as are those of fishes and amphibians.
In an embryo, nerve cells grow out from the spinal cord and form connections with the muscles they will eventually control. What mechanisms described in this chapter might explain how these cells "know" where to go and which cells to connect with?
The nerve cells may follow chemical trails to the muscle cells and identify and attach to them by means of specific surface proteins.
How are the ovulation cycle and the menstruation cycle coordinated?
The processes regulate each other through a system that involves four major hormones.
The onset of menstruation is triggered by __________. Hint 1. Estrogen and progesterone promote the thickening of the endometrium in the uterus.
a drop in the levels of progesterone and estrogen If implantation of an embryo does not occur within a few days, the corpus luteum stops secreting progesterone and estrogen. This leads to disintegration of the endometrium.
How does a zygote differ from a mature egg? a. A zygote has more chromosomes. b. A zygote is smaller. c. A zygote consists of more than one cell. d. A zygote divides by meiosis.
a. A zygote has more chromosomes.
Which of the following embryonic membranes forms part of the umbilical cord and contributes to the formation of the urinary bladder? Hint 1. This membrane is also found in birds and reptiles, where it functions in waste disposal.
allantois In birds and reptiles, the allantois is a sac for the disposal of uric acid while in mammals it becomes part of the umbilical cord and part of the urinary bladder.
From a single cell, oogenesis will produce _____.
an ovum and three polar bodies Meiosis I produces one large secondary oocyte and a polar body. These cells divide again during meiosis II, producing a single large ovum and two or three polar bodies.
External fertilization occurs mostly in _____. Hint 1. Consider what is required for the sperm to get to the egg.
aquatic animals External fertilization is observed in aquatic and sometimes moist habitats because in these habitats sperm can swim to the egg through the water.
During oogenesis, polar bodies _____________.
are discarded
Which of the following is a similarity between spermatogenesis and oogenesis?
both involve meiosis and the production of haploid cells
A woman had several miscarriages. Her doctor suspected that a hormonal insufficiency was causing the lining of the uterus to break down, as it does during menstruation, terminating her pregnancies. Treatment with which of the following might help her remain pregnant? a. oxytocin b. follicle-stimulating hormone c. luteinizing hormone d. prolactin
c. luteinizing hormone
After a sperm penetrates an egg, it is important that the vitelline layer separate from the egg so that it can: a. secrete important hormones. b. enable the fertilized egg to implant in the uterus. c. prevent more than one sperm from entering the egg. d. attract additional sperm to the egg.
c. prevent more than one sperm from entering the egg.
In an experiment, a researcher colored a bit of tissue on the outside of a frog gastrula with an orange fluorescent dye. The embryo developed normally. When the tadpole was placed under an ultraviolet light, which of the following glowed bright orange? (Explain your answer.) a. the heart b. the pancreas c. the brain d. the stomach
c. the brain The outer layer in a gastrula is the ectoderm; of the choices given, only the brain develops from ectoderm.
Which reproductive method is used most frequently by mammals? Hint 1. You are a mammal.
internal fertilization In mammals the sperm are deposited within the female's body, and the resulting zygote develops into a fetus. Nearly all terrestrial animals exhibit internal fertilization, which is an adaptation that enables sperm to reach an egg despite a dry external environment.
PID _____. Hint 1. PID is an acronym for "pelvic inflammatory disease."
is the result of STIs caused by bacterial infections PID is the secondary result of STIs (sexually transmitted infections) caused by bacterial infections.
What does the y-axis in the top panel represent?
levels of pituitary hormones
A rapid increase in the _____ level stimulates ovulation.
luteinizing hormone A surge in LH levels is responsible for triggering ovulation.
The hormone that initiates the development of specialized cells in the ovaries of women and triggers androgen production by the testes of men is _____. Hint 1. Review the regulatory hormones in males and females, and the changes they cause in each.
luteinizing hormone (LH) Following ovulation, LH stimulates the transformation of the follicular tissue in the ovary to form the corpus luteum. In males, LH stimulates the Leydig cells to produce androgen.
Compared to animals that have separate sexes, an animal that is a hermaphrodite has the advantage of _____. Hint 1. A disadvantage of sexual reproduction is the energy spent attracting a mate.
mating with any other member of its species Organisms with separate sexes reproduce with members of the opposite sex. But hermaphrodites can mate with any other member of the species.
During cleavage, the single large cell of the zygote is converted to a _____. Hint 1. Consider the name given to the hollow balls of cells produced as a result of cleavage.
multicellular blastula consisting of smaller cells Cleavage reduces cell size by dividing the zygote into smaller cells that form the blastula.
Level 1: Knowledge/Comprehension Match each function with the correct structure. 2. Female gonad
ovary
Level 1: Knowledge/Comprehension Match each function with the correct structure. 4. Site of fertilization in humans
oviduct
What is the usual site of the fertilization of an egg cell?
oviduct The oviducts are the usual sites of fertilization.
The uterine contractions during labor are stimulated by _____. Hint 1. One of these hormones is produced by the hypothalamus and secreted into the blood by the posterior pituitary; the others are locally acting hormones.
oxytocin and prostaglandins These hormones stimulate the uterine contractions of labor
There are nearly 30 different disorders of sexual development. Who can have these disorders? Everyday Biology: Male, Female, or Intersex?http://mediaplayer.pearsoncmg.com/assets/xgK_ePZ0XNQ5moIP_NgBpgzfTyZM5hNJ
people with either XX or XY chromosomes
After a human sperm penetrates an egg, a fertilization envelope forms. This membrane _____. Hint 1. Consider the importance of the chromosome number of the zygote.
prevents more than one sperm from entering the egg The fertilization envelope, along with other changes to the egg's surface, prevents the entry of more than one sperm cell into the egg, thus assuring the normal complement of 46 chromosomes per zygote.
Which of the following options lists cell types in the correct order of their appearance during spermatogenesis?
primary spermatocyte, secondary spermatocyte, spermatid, sperm
Level 1: Knowledge/Comprehension Match each function with the correct structure. 7. Secretes seminal fluid
prostate gland
Sperm have several components; the function of the acrosome is to _____. Hint 1. Consider what is required for fertilization.
release an enzyme that breaks down the membrane of the ovum The membrane surrounding the ovum must be digested before penetration of the sperm can occur.
Level 1: Knowledge/Comprehension Match each function with the correct structure. 3. Site of spermatogenesis
testis
Asexual reproduction involves _____. Hint 1. Compare asexual reproduction to sexual reproduction.
the creation of genetically identical offspring by a lone parent Asexual reproduction is reproduction without sex.
During the first trimester, _____. Hint 1. The first trimester is the first three months of development.
the fetus is most vulnerable to exposure to drugs and radiation During the first trimester, organogenesis (organ formation) is taking place. During this time, exposure to certain drugs, radiation, or disease organisms can cause profound effects.
Pregnancy tests detect a hormone in a woman's urine that is present only when an embryo is developing in her uterus. This hormone is secreted by _____. Hint 1. Consider the secretion of HCG.
the placenta Early in pregnancy, HCG is produced by the developing embryo from the chorion, which will ultimately become a portion of the placenta. The chorion, and later placenta, produces human chorionic gonadotropin (HCG), which maintains the corpus luteum and its production of progesterone and estrogen.
Which of the trimesters primarily involve(s) an increase in size and general refinement of the human features? Hint 1. Like building a new home, the greatest changes occur early.
the second and third trimesters The first trimester is a time of radical change. The second and third trimesters primarily involve an increase in size and general refinement of the human features.
What is shed from the body in menstruation?
the thickened endometrium when fertilization has not occurred
The ovaries release increasing levels of estrogen and progesterone immediately after ovulation. This results in _____.
thickening of the endometrium and reduced production of FSH and LH, which feeds back to prevent further ovulation
A sperm performs two functions when fertilizing an egg. A sperm __________. Hint 1. The egg has already undergone most of the events of meiosis.
triggers metabolic activity in the egg starting the process of embryonic development and donates a haploid nucleus to fertilize the egg This burst of metabolic activity in the egg is important to start the process of embryonic development.
Level 1: Knowledge/Comprehension Match each function with the correct structure. 5. Site of human gestation
uterus
A fertilized egg usually implants itself and develops in the _____.
uterus The uterus is the usual site of the implantation and development of the fertilized egg.
Level 1: Knowledge/Comprehension Match each function with the correct structure. 6. Sperm duct
vas deferens
A __________ is a fertilized egg (the diploid cell created by the fusion of sperm and egg).
zygote
Level 1: Knowledge/Comprehension Match each function with the correct structure. 8. Lining of uterus
endometrium
The precise site of embryo implantation in a normal pregnancy is the _____. Hint 1. The embryo implants in this part of the uterus.
endometrium This is the capillary-rich inner wall of the uterus, where implantation is accomplished for the developing human embryo.
Based on the graph, elevated levels of which hormone(s) most likely stimulate the LH/FSH surge just before ovulation?
estrogen
If there is no fertilization, degeneration of the corpus luteum results in a drop in _____, which results in the sloughing off of the uterus's endometrium.
estrogen and progesterone Estrogen and progesterone are responsible for maintaining the endometrium in the event that the egg has been fertilized.
After ovulation, high levels of _____ inhibit _____ secretion.
estrogen and progesterone ... FSH and LH By secreting estrogen and progesterone, the corpus luteum maintains the endometrium and inhibits FSH and LH secretion.
Developing ovarian follicles primarily secrete _____.
estrogens Developing ovarian follicles secrete estrogen.
The completion of meiosis II during oogenesis occurs at ________________.
fertilization
Level 1: Knowledge/Comprehension Match each function with the correct structure. 1. Turns into the corpus luteum
follicle
In spermatogenesis, each primary spermatocyte gives rise to _____ sperm. Hint 1. Sperm are produced by meiosis.
four Each diploid primary spermatocyte gives rise to four haploid sperm.
A __________ is a haploid sex cell (a sperm in males and an egg in females).
gamete
Gametogenesis is to spermatogenesis and oogenesis as _____________________.
gonads are to testes and ovaries
If there is fertilization, secretion of _____ by the early embryo maintains the corpus luteum.
human chorionic gonadotropin HCG, secreted by the early embryo, maintains the corpus luteum. The corpus luteum secretes estrogen and progesterone, which maintain the endometrium for implantation.
What are the four major hormones that coordinate the process of the ovulation cycle and the menstruation cycle?
- estrogen - progesterone - FSH - LH
Level 1: Knowledge/Comprehension Match each function with the correct structure. 1. Turns into the corpus luteum 2. Female gonad 3. Site of spermatogenesis 4. Site of fertilization in humans 5. Site of human gestation 6. Sperm duct 7. Secretes seminal fluid 8. Lining of uterus a. vas deferens b. prostate gland c. endometrium d. testis e. follicle f. uterus g. ovary h. oviduct
1. Turns into the corpus luteum - e. follicle 2. Female gonad - g. ovary 3. Site of spermatogenesis - d. testis 4. Site of fertilization in humans - h. oviduct 5. Site of human gestation - f. uterus 6. Sperm duct - a. vas deferens 7. Secretes seminal fluid - b. prostate gland 8. Lining of uterus - c. endometrium
Ovulation usually occurs on or about day _____ of a 28-day ovarian cycle.
14 Ovulation usually occurs about halfway through the 28-day ovarian cycle.
About _____ of couples who want children are unable to conceive. Hint 1. Couples are considered infertile if they are unable to conceive after 12 months of unprotected intercourse.
15% This percentage may grow higher in the future as more women wait until after the age of 35 to have children.
Which of the following statements about sexually transmitted diseases (STDs) is FALSE? - The ability to transmit viral STDs remains a possibility throughout a person's life. - Viral STDs are not curable. - Genital warts are caused by a bacterium. - A virus causes herpes. Hint 1. Antibiotics are not used to treat AIDS, herpes, or genital warts.
FALSE: Genital warts are caused by a bacterium. This is the FALSE statement. A virus causes genital warts.
Which of the following statements about gametogenesis in humans is FALSE? - After ovulation, the follicle cells remaining behind from the ruptured follicle form the corpus luteum. - The result of ovulation is a secondary oocyte that does not complete meiosis until after it is penetrated by a sperm. - Oogenesis begins prior to birth. - In sexually mature adults, spermatogenesis and oogenesis produce about the same number of gametes each day Hint 1. Consider figures below and compare the processes of gametogenesis in males and females. Remember the differences in the products of these processes.
FALSE: In sexually mature adults, spermatogenesis and oogenesis produce about the same number of gametes each day This is the FALSE statement. Women produce about one secondary oocyte a month. Men produce millions of sperm each day
Which of the following statements about reproductive technology and infertility is FALSE? - Only about 2% of couples are unable to conceive after one year of trying to get pregnant. - Abnormally shaped sperm or a low sperm count may lead to infertility. - During in vitro fertilization, fertilization occurs in a laboratory culture dish. - In the ART (assisted reproductive technology) procedure, fertilization occurs after secondary oocytes are removed from the ovaries, stimulated with hormones, fertilized, and returned. Hint 1. Infertility is a surprisingly common problem.
FALSE: Only about 2% of couples are unable to conceive after one year of trying to get pregnant. This is the FALSE statement. About 15% of couples are unable to conceive after one year of trying to get pregnant.
The anterior pituitary gland, under the control of the hypothalamus, produces _____, which stimulate _____.
FSH and LH ... egg maturation and ovulation
__________ is the fusion of two haploid sex cells (sperm and egg) to form a diploid cell.
Fertilization
Gender identity is a person's personal sense of being a man or a woman. Katie says at the end of the clip that, given the traditional definitions of sex, she can't say whether her sex is male or female, but that her gender identity is definitely that of a woman. What does this indicate about gender identity? Everyday Biology: Male, Female, or Intersex?http://mediaplayer.pearsoncmg.com/assets/xgK_ePZ0XNQ5moIP_NgBpgzfTyZM5hNJ
Gender identity is mostly likely the result of a combination of physical, physiological, and social factors.
How would the right-hand side of this graph be altered if pregnancy occurred? What other hormone is responsible for triggering this change?
If pregnancy occurs, the embryo produces human chorionic gonadotropin (hCG), which maintains the corpus luteum, keeping levels of estrogen and progesterone high.
Which of the following is a difference between oogenesis and spermatogenesis? Hint 1. Only women have a menstrual cycle.
In sexually mature adults, oogenesis happens during monthly cycles whereas spermatogenesis occurs continuously. Women typically produce one gamete, roughly every 28 days that has the potential to be fertilized. Men can produce millions of sperm per day that are capable of fertilization.
A surge in estrogen levels correlates with a surge in progesterone levels.
Not supported
Which of the following is a function of oxytocin? - Oxytocin stimulates the urinary tract to make prostaglandins. - Oxytocin maintains the corpus luteum during pregnancy. - Oxytocin stimulates powerful contractions of smooth muscles in the wall of the uterus. - Oxytocin stops the secretion of milk.
Oxytocin stimulates powerful contractions of smooth muscles in the wall of the uterus These contractions serve to expel the fetus from the uterus.
__________ is the creation of genetically unique offspring by two parents.
Sexual reproduction
Which of the following is the best option if Katie wants to have children? Everyday Biology: Male, Female, or Intersex?http://mediaplayer.pearsoncmg.com/assets/xgK_ePZ0XNQ5moIP_NgBpgzfTyZM5hNJ
She can adopt children.
In the video, the narrator says that Katie had her testes removed, and now takes pills to give her more appropriate hormones. What is the most likely explanation? Everyday Biology: Male, Female, or Intersex?http://mediaplayer.pearsoncmg.com/assets/xgK_ePZ0XNQ5moIP_NgBpgzfTyZM5hNJ
Since Katie has no ovaries to produce estrogen, she likely takes an estrogen supplement that supports her gender identity.
Should parents undergoing in vitro fertilization have the right to choose which embryos to implant based on genetic criteria, such as the presence or absence of disease-causing genes? Should they be able to choose based on the sex of the embryo? How could you distinguish acceptable from unacceptable criteria? Do you think such options should be legislated?
Some issues and questions to consider: What characteristics might parents like to select for? If parents had the right to choose embryos based on these characteristics, what are some of the possible benefits? What are potential pitfalls? Could an imbalance of the population result?
TRUE or FALSE: A virus causes genital warts.
TRUE
TRUE or FALSE: A virus causes herpes.
TRUE
TRUE or FALSE: Abnormally shaped sperm or a low sperm count may lead to infertility.
TRUE
TRUE or FALSE: Antibiotics are not used to treat AIDS, herpes, or genital warts.
TRUE
TRUE or FALSE: During in vitro fertilization, fertilization occurs in a laboratory culture dish.
TRUE
TRUE or FALSE: Extraembryonic membrane and its function: The allantois is the site of a mammal's waste disposal.
TRUE
TRUE or FALSE: Extraembryonic membrane and its function: The amnion encloses an embryonic mammal in a fluid-filled sac.
TRUE
TRUE or FALSE: Extraembryonic membrane and its function: The chorion forms part of a mammal's placenta.
TRUE
TRUE or FALSE: Implantation occurs about a week after fertilization.
TRUE
TRUE or FALSE: In the ART (assisted reproductive technology) procedure, fertilization occurs after secondary oocytes are removed from the ovaries, stimulated with hormones, fertilized, and returned.
TRUE
TRUE or FALSE: Only a mammal develops a placenta.
TRUE
TRUE or FALSE: The ability to transmit viral STDs remains a possibility throughout a person's life.
TRUE
TRUE or FALSE: The blastocyst consists of the trophoblast and inner cell mass, each of which has a different developmental fate.
TRUE
TRUE or FALSE: The trophoblast cells release enzymes that promote implantation.
TRUE
TRUE or FALSE: The trophoblast stage implants in the endometrium.
TRUE
TRUE or FALSE: Viral STDs are not curable
TRUE
TRUE or FALSE: In relation to gametogenesis in humans, after ovulation, the follicle cells remaining behind from the ruptured follicle form the corpus luteum.
TRUE After ovulation, the follicle cells remaining behind from the ruptured follicle form the corpus luteum.
TRUE or FALSE: DNA replication occurs during cleavage.
TRUE Cleavage is a stage of development characterized by a rapid increase in cell number.
TRUE or FALSE: In relation to gametogenesis in humans, oogenesis begins prior to birth.
TRUE Oogenesis begins prior to birth.
TRUE or FALSE: In relation to gametogenesis in humans, the result of ovulation is a secondary oocyte that does not complete meiosis until after it is penetrated by a sperm.
TRUE The result of ovulation is a secondary oocyte that does not complete meiosis until after it is penetrated by a sperm.
TRUE or FALSE: A function of oxytocin: Oxytocin stimulates powerful contractions of smooth muscles in the wall of the uterus
TRUE These contractions serve to expel the fetus from the uterus
TRUE or FALSE: When comparing oogenesis and spermatogenesis, a mature ovum is not produced in the absence of sperm, but sperm are produced regardless of what the ova are doing.
TRUE When comparing oogenesis and spermatogenesis, a mature ovum is not produced in the absence of sperm, but sperm are produced regardless of what the ova are doing. The final meiotic division of a secondary oocyte will occur only when a sperm has connected to the oocyte's cell membrane
TRUE or FALSE: In relation to gametogenesis in humans, women produce about one secondary oocyte a month. Men produce millions of sperm each day.
TRUE Women produce about one secondary oocyte a month. Men produce millions of sperm each day.
Which of the comparisons between oogenesis and spermatogenesis is accurate? - Primary oocytes and primary spermatocytes follow a similar pattern of development through meiosis. - Luteinizing hormone triggers ovulation in females and has no other role in reproduction. - A mature ovum is not produced in the absence of sperm, but sperm are produced regardless of what the ova are doing. - Follicle-stimulating hormone promotes only egg, not sperm, development.
TRUE: A mature ovum is not produced in the absence of sperm, but sperm are produced regardless of what the ova are doing. The final meiotic division of a secondary oocyte will occur only when a sperm has connected to the oocyte's cell membrane.
What prevents menstruation when a woman first becomes pregnant? Hint 1. A new source of hormones prevents the hormonal changes that trigger menstruation.
The release of HCG from the implanted embryo stimulates the corpus luteum to continue to secrete progesterone and estrogen. Human chorionic gonadotropin (HCG) is typically the substance tested for in pregnancy tests.
As a frog embryo develops, the neural tube forms from ectoderm along what will be the frog's back, directly above the notochord. To study this process, a researcher extracted a bit of notochord tissue and inserted it under the ectoderm where the frog's belly would normally develop. What can the researcher hope to learn from this experiment? Predict the possible outcomes. What experimental control would you suggest?
The researcher might find out whether chemicals from the notochord stimulate the nearby ectoderm to become the neural tube, a process called induction. Transplanted notochord tissue might cause ectoderm anywhere in the embryo to become neural tissue. Possible control experiment: Transplant non-notochord tissue under the ectoderm of the belly area.
Two mammals of different species mate, but the mating does not produce offspring. Which of the following could explain this occurrence? - The sperm cannot penetrate the jelly coat inside of the egg's plasma membrane. - The sperm of different species cannot bind to receptors on the egg cell. - The sperm are not the correct size. - The sperm do not possess acrosomes Hint 1. This is a form of prezygotic barrier mechanism.
The sperm of different species cannot bind to receptors on the egg cell. Even if members of different species do happen to mate, the production of offspring can be blocked because the sperm simply cannot access the egg.
Which of the following statements about early human development is FALSE? - Implantation occurs about a week after fertilization. - The trophoblast cells release enzymes that promote implantation. - The trophoblast cells will form the baby. - The trophoblast stage implants in the endometrium. Hint 1. The blastocyst consists of the trophoblast and inner cell mass, each of which has a different developmental fate.
The trophoblast cells will form the baby. This is the FALSE statement. Only cells of the inner cell mass form the baby.
Which of the following INCORRECTLY pairs up an extraembryonic membrane with its function? - The yolk sac provides a developing human embryo with nourishment. - The chorion forms part of a mammal's placenta. - The allantois is the site of a mammal's waste disposal. - The amnion encloses an embryonic mammal in a fluid-filled sac Hint 1. Only a mammal develops a placenta.
The yolk sac provides a developing human embryo with nourishment. This is the INCORRECTLY matched pair. This is true of chicks, but in humans the yolk sac produces the embryo's first blood and germ cells.
Birth control pills contain synthetic estrogen and progesterone. How might these hormones prevent pregnancy? Hint 1. Consider how these hormones interact with other hormones in affecting the female reproductive cycle.
They keep the pituitary from secreting FSH and LH, so ovulation does not occur. Estrogen and progesterone are maintained at high concentrations during pregnancy and provide negative feedback that suppresses the release of FSH and LH. This type of birth control pill mimics pregnancy.
After ovulation occurs, the empty follicle _____.
changes into the corpus luteum and makes hormones The pituitary hormone LH triggers ovulation, the rupture of the follicle and expulsion of the secondary oocyte. The ruptured follicle then develops into a corpus luteum. LH also promotes the secretion of progesterone and estrogen by the corpus luteum.
Cell divisions called _____ proceed so rapidly in the developing embryo that there is no growth of the cells between divisions. Hint 1. Consider the process in which the multicellular embryo is produced from the zygote.
cleavage Cleavage is a succession of rapid cell divisions that follows fertilization; during cleavage the embryo does not enlarge.
What does the x-axis of this graph represent?
days since the start of the last cycle
In general, chromosomes in human body cells are _____. Hint 1. Our cells result from the fusion of gametes.
diploid, except for gametes Human somatic cells are diploid, and meiosis produces haploid gametes.
In the process of gastrulation, three embryonic tissue layers become established. From outermost to deepest, these three embryonic layers are _____. Hint 1. Ectoderm gives rise to skin, mesoderm gives rise to muscle and bone, and endoderm produces the lining of the gut.
ectoderm, mesoderm, and endoderm This makes sense when you consider the location of tissues that arise from each.