1. Reproduction Ch 27

2. 27.1 Asexual reproduction results in the generation of genetically identical offspring
What kinds of environments would likely be advantageous to asexually reproducing organisms? Why?
Types of asexual reproduction:
budding
fission
fragmentation
parthenogenesis
Checkpoint Question Response
Stable environments favor asexual reproduction because genotypes that are well adapted to the local environment are perpetuated in the offspring.
Student Misconceptions and Concerns
Students often do not understand the costs and benefits of asexual and sexual reproduction. Consider discussing the advantages and disadvantages of each of these forms of reproduction. Encourage students to focus on the compromises involved in any adaptation. There is simply no one “best” way for all animals to reproduce. (27.1–27.2)
Teaching Tips
Aphid life cycles usually alternate between asexual and sexual reproductive strategies during a single year. Consider challenging your class to explain why aphids (and other animals) do this. In general, sexual reproduction is most common in times of stress and may be related to overpopulation or environmental change in which diversity may be favored. (27.1)
Active Lecture Tips
Before beginning to address reproductive biology, ask students to work in pairs to describe the advantages of asexual and sexual reproduction. What are the advantages and disadvantages of each? Have students write out their ideas on paper and turn them in. Reading over their ideas will provide a good background for your future class discussions on this topic. (27.1–27.2)

3. 27.2 Sexual reproduction results in the generation of genetically unique offspring
Sexual reproduction is the creation of offspring through the process of fertilization, the union of sperm and egg. Both sperm and egg are gametes, sex cells with a haploid (n) set of chromosomes.
The male gamete, the sperm
Size?
Motile?
The female gamete, the egg,
When egg and sperm join, they form a diploid (2n) ___________, or fertilized egg.
Student Misconceptions and Concerns
Students often do not understand the costs and benefits of asexual and sexual reproduction. Consider discussing the advantages and disadvantages of each of these forms of reproduction. Encourage students to focus on the compromises involved in any adaptation. There is simply no one “best” way for all animals to reproduce. (27.1–27.2)
Many students expect that hermaphroditic animals simply fertilize themselves. Although this may be common in some animals, the exchange of gametes between hermaphrodites also occurs, as noted in the text. (27.2)
Teaching Tips
Many salamander species use spermatophores to transfer sperm from the male to the female. Spermatophores are reproductive structures produced by males during courtship. Sperm is deposited atop a gelatinous base attached to the substrate. The female moves over the spermatophore, removes some or all of the sperm from the cap, and stores the sperm in her reproductive tract (a spermatheca) until the time of egg deposition. Thus, sperm transfer is external but fertilization is internal. (27.2)
Active Lecture Tips
Before beginning to address reproductive biology, ask students to work in pairs to describe the advantages of asexual and sexual reproduction. What are the advantages and disadvantages of each? Have students write out their ideas on paper and turn them in. Reading over their ideas will provide a good background for your future class discussions on this topic. (27.1–27.2)

4. 27.2 Sexual reproduction results in the generation of genetically unique offspring
Sexual reproduction results in genetic variation among offspring. This may enhance survival of a population in a changing environment.
The process of _______________ produces gametes.
3 ways genetic diversity is enhanced
1. 2 parent contribute
2. __________ __________ in prophase I
3. Chromosome alignment possibilities in metaphase I.
Checkpoint Question Response
The offspring of sexual reproduction are genetically diverse, whereas the offspring of asexual reproduction are genetically identical.
Student Misconceptions and Concerns
Students often do not understand the costs and benefits of asexual and sexual reproduction. Consider discussing the advantages and disadvantages of each of these forms of reproduction. Encourage students to focus on the compromises involved in any adaptation. There is simply no one “best” way for all animals to reproduce. (27.1–27.2)
Many students expect that hermaphroditic animals simply fertilize themselves. Although this may be common in some animals, the exchange of gametes between hermaphrodites also occurs, as noted in the text. (27.2)
Teaching Tips
Many salamander species use spermatophores to transfer sperm from the male to the female. Spermatophores are reproductive structures produced by males during courtship. Sperm is deposited atop a gelatinous base attached to the substrate. The female moves over the spermatophore, removes some or all of the sperm from the cap, and stores the sperm in her reproductive tract (a spermatheca) until the time of egg deposition. Thus, sperm transfer is external but fertilization is internal. (27.2)
Active Lecture Tips
Before beginning to address reproductive biology, ask students to work in pairs to describe the advantages of asexual and sexual reproduction. What are the advantages and disadvantages of each? Have students write out their ideas on paper and turn them in. Reading over their ideas will provide a good background for your future class discussions on this topic. (27.1–27.2)

5. 27.3 The human female reproductive system includes the ovaries and structures that deliver gametes
The human female reproductive system consists of a pair of ovaries, ducts that carry gametes, a uterus, and structures for copulation.
Ovaries
2 functions
Nurture the egg inside the ___________.
Produce _______________/
Oviducts connect the __________ to the uterus
The uterus, where the __________ implants, opens into the vagina, which receives the penis during intercourse and serves as the birth canal.
Student Misconceptions and Concerns
Students’ background knowledge of human reproductive biology is likely to be quite uneven. Furthermore, the embarrassment frequently associated with this topic makes it difficult for teachers to fairly assess what students know. The best advice may be to not assume too much. (27.3–27.8)
Embarrassment with the subject of human reproductive biology may make open discussions uncomfortable for some students. Good clear textbook and media assignments that can be studied privately and opportunities to ask anonymous questions provide additional avenues to address sensitive content and questions. (27.3–27.8)
Teaching Tips
Ectopic pregnancies occur when an embryo implants anywhere other than the uterus. Most frequently, ectopic pregnancies occur in the oviducts. However, the structure of the oviduct cannot accommodate the growth of a fetus. Surgical removal of the fetus, resulting in an abortion, is thus often required for the sake of the mother’s health. Many of those who believe that abortion is wrong in general may consider abortions acceptable in the case of an ectopic pregnancy, in that it may literally save the life of the mother. (27.3)
Endometriosis is an inflammatory condition in which the endometrium spreads beyond the uterus. It can lead to painful menstrual cycles and infertility. The Endometriosis Association website, is a good resource for additional information. (27.3)

6. Oviduct Ovaries Follicles Corpus luteum Uterus Wall of uterus
Endometrium
(lining of uterus)
Cervix
(“neck” of uterus)
Figure 27.3a Front view of female reproductive anatomy (upper portion)
Vagina

7. 27.4 The human male reproductive system includes the testes and structures that deliver gametes
Testes (singular, testis) are each housed outside the abdominal cavity in a sac called the scrotum.
The epididymis stores _____________ as they develop further. During ejaculation, sperm leave the epididymis through the ____ _______________.
The seminal vesicles, prostate gland, and bulbourethral glands contribute to semen, the fluid ejaculated along with the _________ from the penis during male orgasm.
Student Misconceptions and Concerns
Students’ background knowledge of human reproductive biology is likely to be quite uneven. Furthermore, the embarrassment frequently associated with this topic makes it difficult for teachers to fairly assess what students know. The best advice may be to not assume too much. (27.3–27.8)
Embarrassment with the subject of human reproductive biology may make open discussions uncomfortable for some students. Good clear textbook and media assignments that can be studied privately and opportunities to ask anonymous questions provide additional avenues to address sensitive content and questions. (27.3–27.8)
Teaching Tips
Men in your class will be well aware of physiological changes in the scrotum associated with thermoregulation. When a man enters cool water, the scrotum is pulled tight and the testes are held close to the body. During a warm shower or bath, the scrotum relaxes and the testes are held far away from the body. This is one of the reasons that testicular self-exams are recommended during a warm shower. (27.4)
Testicular cancer is the most common form of cancer in men between 15 and 35 years of age. Students can find information about testicular cancer and how to perform a self-exam at the website for the American Cancer Society at (27.4)
Students often confuse what is meant by the terms “semen” and “sperm.” Most of a human ejaculate consists of glandular products. In fact, there is no visible difference to the naked eye between the ejaculate of a fertile man and that of a sterile man. (27.4)

8. 27.4 The human male reproductive system includes the testes and structures that deliver gametes
The human penis consists mainly of cylinders of erectile tissue that can fill with blood to cause an erection during sexual arousal.
Sperm production by the testes is controlled by hormones from the hypothalamus and pituitary.
Student Misconceptions and Concerns
Students’ background knowledge of human reproductive biology is likely to be quite uneven. Furthermore, the embarrassment frequently associated with this topic makes it difficult for teachers to fairly assess what students know. The best advice may be to not assume too much. (27.3–27.8)
Embarrassment with the subject of human reproductive biology may make open discussions uncomfortable for some students. Good clear textbook and media assignments that can be studied privately and opportunities to ask anonymous questions provide additional avenues to address sensitive content and questions. (27.3–27.8)
Teaching Tips
Men in your class will be well aware of physiological changes in the scrotum associated with thermoregulation. When a man enters cool water, the scrotum is pulled tight and the testes are held close to the body. During a warm shower or bath, the scrotum relaxes and the testes are held far away from the body. This is one of the reasons that testicular self-exams are recommended during a warm shower. (27.4)
Testicular cancer is the most common form of cancer in men between 15 and 35 years of age. Students can find information about testicular cancer and how to perform a self-exam at the website for the American Cancer Society at (27.4)
Students often confuse what is meant by the terms “semen” and “sperm.” Most of a human ejaculate consists of glandular products. In fact, there is no visible difference to the naked eye between the ejaculate of a fertile man and that of a sterile man. (27.4)
© 2018 Pearson Education, Inc.

9. Urinary bladder (excretory system) Seminal vesicle (behind bladder)
Prostate gland
Bulbourethral
gland
Urethra
Erectile tissue
of penis
Figure 27.4a Front view of male reproductive anatomy
Scrotum
Vas deferens
Testicle
Testis
Epididymis
Glans

10. 27.5 The formation of sperm and egg cells requires meiosis
Spermatogenesis and oogenesis ( 2 forms of meiosis) produce sperm and eggs, respectively.
Primary spermatocytes are made continuously in the testes.
These diploid cells undergo meiosis to form four haploid sperm.
In females, each month, one primary oocyte forms a secondary oocyte, which, if penetrated by a sperm, completes meiosis and becomes a mature egg.
The haploid nucleus of the mature egg then fuses with the haploid nucleus of the sperm, forming a diploid zygote.
Student Misconceptions and Concerns
Students’ background knowledge of human reproductive biology is likely to be quite uneven. Furthermore, the embarrassment frequently associated with this topic makes it difficult for teachers to fairly assess what students know. The best advice may be to not assume too much. (27.3–27.8)
Embarrassment with the subject of human reproductive biology may make open discussions uncomfortable for some students. Good clear textbook and media assignments that can be studied privately and opportunities to ask anonymous questions provide additional avenues to address sensitive content and questions. (27.3–27.8)
Active Lecture Tips
Ask students to work in pairs or small groups to explain why polar bodies are produced during oogenesis and why they have so little cytoplasm. Challenge your students to explain why polar bodies are not produced in spermatogenesis. (Answer: Polar bodies are produced during oogenesis to eliminate nuclear material. Their smaller size is an adaptation to conserve cytoplasm during reduction division. During spermatogenesis, four functional spermatozoa are produced and no nuclear material is discarded. However, extra cytoplasm is generated when a spherical spermatid becomes an elongate sperm.) (27.5)

11. 27.5 The formation of sperm and egg cells requires meiosis
If an egg is surgically removed from a woman’s ovary, in what stage of meiotic development will that egg be?
Checkpoint Question Response
A mature egg within the ovary (a secondary oocyte) is arrested at metaphase II.
Student Misconceptions and Concerns
Students’ background knowledge of human reproductive biology is likely to be quite uneven. Furthermore, the embarrassment frequently associated with this topic makes it difficult for teachers to fairly assess what students know. The best advice may be to not assume too much. (27.3–27.8)
Embarrassment with the subject of human reproductive biology may make open discussions uncomfortable for some students. Good clear textbook and media assignments that can be studied privately and opportunities to ask anonymous questions provide additional avenues to address sensitive content and questions. (27.3–27.8)
Active Lecture Tips
Ask students to work in pairs or small groups to explain why polar bodies are produced during oogenesis and why they have so little cytoplasm. Challenge your students to explain why polar bodies are not produced in spermatogenesis. (Answer: Polar bodies are produced during oogenesis to eliminate nuclear material. Their smaller size is an adaptation to conserve cytoplasm during reduction division. During spermatogenesis, four functional spermatozoa are produced and no nuclear material is discarded. However, extra cytoplasm is generated when a spherical spermatid becomes an elongate sperm.) (27.5)

12. Mature sperm released into center of seminiferous tubule
Penis
Epididymis
Seminiferous
tubule
Testis
Scrotum
Testis
Mitotic divisions
continuously
produce new cells
Diploid cell 2n
Differentiation and
onset of meiosis I
Primary
spermatocyte
(diploid; in prophase
of meiosis I) 2n
Cross section of
seminiferous tubule
Meiosis I completed
Secondary
spermatocyte
(haploid) n n
Figure 27.5a Spermatogenesis
Meiosis II
Developing
sperm cells n n n n
Cellular
differentiation
Sperm cells
(haploid) n n n n
Mature sperm released into center
of seminiferous tubule

13. Brain
The testes produce __________ and hormones. How does the hypothalamus control the production of FHS and LH? What is the function of FSH and LH?
Stimuli from other
areas in the brain
Hypothalamus
Releasing
hormone
Anterior
pituitary
Negative feedback
Figure 27.4c Hormonal control of the testis by the hypothalamus
Negative feedback
FSH LH
Androgen = male hormones, testosterone is an example
Androgen
production
Testis
Sperm
production

14. 27.6 Hormones synchronize cyclic changes in the ovary and uterus
Oogenesis is one part of a female mammal’s reproductive cycle, a recurring sequence of events that
produces gametes, makes them available for fertilization, and
prepares the body for pregnancy.
The reproductive cycle is actually two closely linked cycles.
The ______________cycle controls the growth and release of an egg.
During the ____________cycle, the uterus is prepared for possible implantation of an embryo.
Student Misconceptions and Concerns
Students’ background knowledge of human reproductive biology is likely to be quite uneven. Furthermore, the embarrassment frequently associated with this topic makes it difficult for teachers to fairly assess what students know. The best advice may be to not assume too much. (27.3–27.8)
Embarrassment with the subject of human reproductive biology may make open discussions uncomfortable for some students. Good clear textbook and media assignments that can be studied privately and opportunities to ask anonymous questions provide additional avenues to address sensitive content and questions. (27.3–27.8)
Teaching Tips
Students might wonder why a woman’s body goes through menstrual cycles. Why not just sustain the endometrium continuously? One hypothesis suggests that because the uterus is an environment in which bacteria can grow, menstrual cycles are a way to “flush” the system and discourage microbial growth. (27.6)
Many home pregnancy tests rely on antibodies to HCG. (27.6)
Active Lecture Tips
See the Activity “Applying Understanding of Female Hormones to Birth Control” on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. (27.6–27.8)

15. 27.6 Hormones synchronize cyclic changes in the ovary and uterus
Approximately every 28 days, the hypothalamus signals the __________to secrete FSH and LH, which trigger the growth of a _________ and ovulation
The follicle becomes the _________ _______, which secretes estrogen and progesterone.
These two hormones stimulate the endometrium (the uterine lining) to thicken, preparing the uterus for implantation, and inhibit the hypothalamus, reducing FSH and LH secretion.
Student Misconceptions and Concerns
Students’ background knowledge of human reproductive biology is likely to be quite uneven. Furthermore, the embarrassment frequently associated with this topic makes it difficult for teachers to fairly assess what students know. The best advice may be to not assume too much. (27.3–27.8)
Embarrassment with the subject of human reproductive biology may make open discussions uncomfortable for some students. Good clear textbook and media assignments that can be studied privately and opportunities to ask anonymous questions provide additional avenues to address sensitive content and questions. (27.3–27.8)
Teaching Tips
Students might wonder why a woman’s body goes through menstrual cycles. Why not just sustain the endometrium continuously? One hypothesis suggests that because the uterus is an environment in which bacteria can grow, menstrual cycles are a way to “flush” the system and discourage microbial growth. (27.6)
Many home pregnancy tests rely on antibodies to HCG. (27.6)
Active Lecture Tips
See the Activity “Applying Understanding of Female Hormones to Birth Control” on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. (27.6–27.8)

16. 27.6 Hormones synchronize cyclic changes in the ovary and uterus
If the egg is not fertilized, the drop in LH shuts down the corpus luteum and its hormones.
This triggers menstruation, the breakdown of the endometrium.
The hypothalamus and pituitary then stimulate another follicle, starting a new cycle.
If fertilization occurs, a hormone from the embryo maintains the uterine lining and prevents menstruation.
Student Misconceptions and Concerns
Students’ background knowledge of human reproductive biology is likely to be quite uneven. Furthermore, the embarrassment frequently associated with this topic makes it difficult for teachers to fairly assess what students know. The best advice may be to not assume too much. (27.3–27.8)
Embarrassment with the subject of human reproductive biology may make open discussions uncomfortable for some students. Good clear textbook and media assignments that can be studied privately and opportunities to ask anonymous questions provide additional avenues to address sensitive content and questions. (27.3–27.8)
Teaching Tips
Students might wonder why a woman’s body goes through menstrual cycles. Why not just sustain the endometrium continuously? One hypothesis suggests that because the uterus is an environment in which bacteria can grow, menstrual cycles are a way to “flush” the system and discourage microbial growth. (27.6)
Many home pregnancy tests rely on antibodies to HCG. (27.6)
Active Lecture Tips
See the Activity “Applying Understanding of Female Hormones to Birth Control” on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. (27.6–27.8)

17. Control by hypothalamus Inhibited by combination of
estrogen and progesterone
Hypothalamus
Stimulated by high levels
of estrogen
Releasing hormone
Anterior pituitary
Figure 27.6_1 The reproductive cycle of the human female (part 1) 2
FSH LH

18. B Pituitary hormones in blood 5 LH peak triggers ovulation and
corpus luteum
formation 7 LH
FSH
Figure 27.6_2 The reproductive cycle of the human female (part 2)
FSH stimulates
follicle to grow
LH surge
triggers ovulation 3 1 5 10
14 15 20 25 28
Day
Menstruation

19. FSH stimulates follicle to grow LH surge triggers ovulation 3
C Ovarian cycle 6
Growing follicle
Corpus
luteum
Degenerating
corpus luteum
Mature
follicle
Ovulation
Pre-ovulatory phase
Post-ovulatory phase
Figure 27.6_3 The reproductive cycle of the human female (part 3)
Estrogen secreted
by growing follicle
Progesterone and
estrogen secreted
by corpus luteum 1 5 10
14 15 20 25 28
Day
Menstruation

20. Pre-ovulatory phase Post-ovulatory phase Estrogen secreted
by growing follicle
Progesterone and
estrogen secreted
by corpus luteum
Peak causes
LH surge D
Ovarian
hormones
in blood 4 8
Estrogen
Progesterone
Figure 27.6_4 The reproductive cycle of the human female (part 4)
Progesterone and
estrogen promote
thickening of
endometrium
Low levels of
estrogen trigger
menstruation 1 5 10
14 15 20 25 28
Day
Menstruation

21. Progesterone and estrogen promote thickening of endometrium
Low levels of
estrogen trigger
menstruation E
Menstrual cycle 1
Endometrium
Figure 27.6_5 The reproductive cycle of the human female (part 5) 1 5 10
14 15 20 25 28
Day
Menstruation

22. Fertilization of mature egg by sperm Cleavage starts Trophoblast
UTERINE
Blastocyst
CAVITY
Cavity
Ovary
Inner cell mass
Blastocyst
(implanted)
Uterine
cavity
Oviduct
Endometrium
Secondary
oocyte
Figure 27.15ab From ovulation to implantation (with inset of blastocyst, 6 days after conception)
Uterus
Ovulation

23. You should now be able to
Compare the types, advantages, and disadvantages of asexual and sexual reproduction.
Describe the structures and functions of the female and male human reproductive systems.
Describe and compare the processes and products of spermatogenesis and oogenesis.
State the hormones that control the production of sperm and androgen.
Describe the events of and control of the menstrual cycle. (State the hormones and their function)