Notes to Instructors
Chapter 46 Animal Reproduction
What is the focus of this activity?
This activity highlights both the similarities and differences in the reproductive systems
What is this particular activity designed to do?
Activity 46.1 How does the production of male and female gametes differ in human
males and females?
What misconceptions or difficulties can this activity reveal?
Activity 46.1
Many students do not understand the mechanisms that control gamete production in
Answers
Activity 46.1 How does the production of male and female
gametes differ in human males and females?
This activity is designed to help you understand how gamete production is controlled in
mammals and particularly in humans.
Notes to Instructors 305
Using all the terms below, diagram the control of gamete and sex hormone production
first in a human male and then in a human female. Be sure to explain the role(s) of each
term in your diagram.
306 Activity 46.1
hypothalamus
anterior pituitary
LH
FSH
ovary or testes
follicle or seminiferous tubule
corpus luteum or Leydig cells
progesterone
estrogen or testosterone
secondary sex characteristics
primary sex characteristics
negative feedback
egg and polar bodies or sperm
Human male:
Human female:
Use your diagrams to answer the questions.
1. In both males and females, the hypothalamus produces GnRH, which stimulates the
pitutitary to release LH and FSH. Fill in the chart.
Hormone a. In males causes: b. In females causes:
LH LH stimulates the Leydig cells of
the testes to produce testosterone
LH stimulates ovulation.
Following ovulation, LH causes
3. Most birth control methods are designed to keep the egg and sperm from uniting to
form a zygote. Many birth control pills or patches used by human females contain a
combination of estrogen and progesterone. How do they keep sperm from uniting
with egg? Explain the mechanism.
The set of 28 pills usually includes 21 pills that contain a combination of estradiol
4. Efforts to make a male contraceptive pill (analogous to the pills used by females)
have not been very successful. Given what you know about the similarities and
differences in male and female gamete production, propose why this might be
the case.
In human males, the levels of testosterone (and other androgens) directly affect
Activity 46.1 307
2. In both males and females, the testes or ovaries produce additional hormones.
Hormones
a. Males produce: b. Females produce:
Testosterone and other
androgens
Estrogens and progesterone
Prior to puberty, these
Prior to puberty, these
5. Fertilization generally occurs in the upper third of the oviduct, and development of
the fetus occurs in the uterus. In some relatively rare cases, however, developing
embryos have attached to the outside of the uterus and developed there for the full
nine months of pregnancy.
a. Given the anatomy of the female reproductive system, can you explain how this
could happen?
In the human female, the fallopian tubes or oviducts are not directly attached to
b. What modifications of normal birthing procedures (if any) would have to be
made in such cases?
Because the baby is not inside the uterus, it cannot be delivered normally
308 Activity 46.1
46.1 Test Your Understanding
1 to 3. In an experiment, an adult rat’s testes, including the vascular connections, were
transplanted to the wall of the abdomen. Connections of the testes to the
reproductive tract were cut/severed.
Following recovery, which of the following would be true for this rat? Explain your
answers.
T/F 3. The rat would have normal sexual activity but have no sperm in the ejaculate.
True—As noted above, an ejaculate would be formed, but no sperm would be
present because the connection to the testes was severed.
4. A girl begins to develop breasts and pubic hair at the age of four. Given these
symptoms, her physician orders a CT scan (imaging procedure) to look for an
endocrine tumor. Which organ would he most likely not investigate as the cause?
Explain your reasoning.
a. hypothalamus
b. pituitary
c. ovary
d. uterus
Hyperactivity of the hypothalamus, pituitary, or ovary, in the form of a tumor, could
5 to 8. Assume that women can be vaccinated against the following hormones. Each
vaccine is designed to completely neutralize the target hormone’s activity. Which
vaccine(s) would prevent pregnancy? Explain your answers.
A ⴝWould prevent pregnancy; B ⴝwould not prevent pregnancy
5. A vaccine against LH
6. A vaccine against CG
7. A vaccine against estrogen
8. A vaccine against prolactin