1. You have discovered a new organism living in tide pools at your favorite beach.
Every so often, one of the creature’s appendages will break off and gradually
grow into a whole new organism, identical to the first. This is an example of—
a. sexual reproduction
b. fission
c. budding
d. parthenogenesis
The correct answer is c—
A. Answer a is incorrect. Sexual reproduction involves genetic contributions from
two parents. This method generates offspring from only one parent.
The correct answer is c—
B. Answer b is incorrect. The process of fission does not involve this type of
reproduction.
The correct answer is c—budding
C. Answer c is correct. Budding is the most appropriate term to describe this type of
reproduction
The correct answer is c—
D. Answer d is incorrect. Parthenogenesis involves the development of offspring
from unfertilized eggs, which is not applicable to this scenario.
2. If you decided that the organism you discovered in question 1 used
parthenogenesis, what would you also know about this species?
a. It is asexual
b. All the individuals are female
c. Each individual develops from an unfertilized egg
d. All of the above are true
The correct answer is d—
A. Answer a is incorrect. It is not the only correct answer.
The correct answer is d—
B. Answer b is incorrect. It is not the only correct answer.
The correct answer is d—
C. Answer c is incorrect. It is not the only correct answer
The correct answer is d—All of the above are true
D. Answer d is correct. All of these answers are true of parthenogenic reproduction.
3. Sequential hermaphroditism differs from general hermaphroditism in that
sequential hermaphrodites—
a. contain the reproductive structures of both sexes
b. may change sexes as the result of social stimuli
c. change species as they mature
d. start as male and change to female
The correct answer is b—
A. Answer a is incorrect. Sequential hermaphrodites only exhibit the reproductive
structures (and behaviors) of one sex at a time.
The correct answer is b—may change sexes as the result of social stimuli
B Answer b is correct. Sequential hermaphrodites use changes in social group
structure as stimulus for changing sexes.
The correct answer is b—
C. Answer c is incorrect. Although sequential hermaphroditism may be influenced by
age, it is apparently not the definitive factor that determines when a female will
become male.
The correct answer is b—
D. Answer d is incorrect. The documented cases of sequential hermaphroditism in
fish always start as females and become male.
4. Which of the following terms describes your first stage as a diploid organism?
a. Sperm
b. Egg
c. Gamete
d. Zygote
The correct answer is d—
A. Answer a is incorrect. Sperm are haploid.
The correct answer is d—
B. Answer b is incorrect. Eggs are haploid.
The correct answer is d—
C. Answer c is incorrect. Gametes (eggs and sperm) are haploid.
The correct answer is d—Zygote
D. Answer d is correct. Zygotes are diploid.
5. In which of the following groups of mammals would a mother not produce milk
to feed her offspring?
a. Monotremes
b. Marsupials
c. Placentals
d. All of the above
The correct answer is d—
A. Answer a is incorrect. Monotremes produce milk, but this is not the only correct
answer.
The correct answer is d—
B. Answer b is incorrect. Marsupials produce milk, but this is not the only correct
answer.
The correct answer is d—
C. Answer c is incorrect. Placentals produce milk, but this is not the only correct
answer.
The correct answer is d—All of the above
D. Answer d is correct. All of the mammal groups produce milk.
6. The major difference between an estrous cycle and a menstrual cycle is that—
a. sexual receptivity occurs only around ovulation in the estrous cycle, but it
can occur during any time of the menstrual cycle
b. estrous cycles occur in reptiles, but menstrual cycles occur in mammals
c. estrous cycles are determined by FSH, but menstrual cycles are
determined by LH
d. estrous cycles occur monthly, but menstrual cycles occur sporadically
The correct answer is a—sexual receptivity occurs only around ovulation in the estrous
cycle, but it can occur during any time of the menstrual cycle
A. Answer a is correct. Sexual receptivity differs in timing between species with
estrous cycles and those with menstrual cycles.
The correct answer is a—
B. Answer b is incorrect. Both estrous and menstrual cycles are found in mammals.
The correct answer is a—
C. Answer c is incorrect. Both estrous and menstrual cycles are dependent on FSH
and LH levels.
The correct answer is a—
D. Answer d is incorrect. Menstrual cycles are as or more likely to occur monthly.
7. Which of the following structures is the site of spermatogenesis?
a. Prostate
b. Bulbourethral gland
c. Urethra
d. Seminiferous tubule
The correct answer is d—
A. Answer a is incorrect. The prostate contributes citric acid (an energy source) to
the formation of semen but is not involved in spermatogenesis.
The correct answer is d—
B. Answer b is incorrect. The bulbourethral gland secretes material that helps to
protect sperm from the acidic vaginal environment, but it does not produce sperm.
The correct answer is d—
C. Answer c is incorrect. The urethra is a conduit that carries either semen or urine
(at any given time) but does not contribute to the formation of either.
The correct answer is d—Seminiferous tubule
D. Answer d is correct. Sperm develops in the seminiferous tubules within the testes.
8. Which of the following is a major difference between spermatogenesis and
oogenesis?
a. Spermatogenesis involves meiosis, and oogenesis involves mitosis.
b. Spermatogenesis is continuous, but oogenesis is variable.
c. Spermatogenesis produces fewer gametes per precursor cell than
oogenesis does.
d. All of the above.
The correct answer is b—
A. Answer a is incorrect. Both spermatogenesis and oogenesis involve meiosis.
The correct answer is b—Spermatogenesis is continuous, but oogenesis is variable.
B. Answer b is correct. One of the major differences between spermatogenesis and
oogenesis is the timing of gametogenesis. Spermatogenesis is continuous, but
oogenesis has several stoppages.
The correct answer is b—
C. Answer c is incorrect. Spermatogenesis actually produces four gametes for each
precursor cell, but one egg precursor generates only one mature egg cell.
The correct answer is b—
D. Answer d is incorrect. Only answer b, timing is an actual difference between
spermatogenesis and oogenesis.
9. FSH and LH are produced by—
a. the ovaries
b. the testes
c. the anterior pituitary
d. the adrenal glands
The correct answer is c—
A. Answer a is incorrect. FSH and LH are not produced by the ovaries; they are
produced by the anterior pituitary.
The correct answer is c—
B. Answer b is incorrect. FSH and LH are not produced by the testes; they are
produced by the anterior pituitary.
The correct answer is c—the anterior pituitary
C. Answer c is correct. FSH and LH are produced by the anterior pituitary in both
males and females.
The correct answer is c—
D. Answer d is incorrect. FSH and LH are not produced by the adrenal glands; they
are produced by the anterior pituitary
10. Gametogenesis is requires the conclusion of meiosis II. When does this occur in
females?
a. During fetal development
b. At the onset of puberty
c. After fertilization
d. After implantation
The correct answer is c—
A. Answer a is incorrect. Oogenesis in females is not completed during development;
it is not until fertilization occurs that meiosis II is completed.
The correct answer is c—
B. Answer b is incorrect. Meiosis II is not completed until after fertilization.
The correct answer is c—After fertilization
C. Answer c is correct. Meiosis II is completed after fertilization.
The correct answer is c—
D. Answer d is incorrect. Meiosis II is completed prior to implantation.
11. Mutations that affect proteins in the acrosome would impede which of the
following functions?
a. Fertilization
b. Locomotion
c. Meiosis
d. Semen production
The correct answer is a—Fertilization
A. Answer a is correct. The acrosomal enzymes are required for the sperm to break
through the barrier surrounding the egg during fertilization.
The correct answer is a—
B. Answer b is incorrect. The acrosomal enzymes are not involved in locomotion.
The correct answer is a—
C. Answer c is incorrect. The acrosomal enzymes are not directly involved in
meiosis; answer a is a better choice.
The correct answer is a—
D. Answer d is incorrect. The acrosomal enzymes are not involved in semen
production.
12. In humans, fertilization occurs in the _________, and implantation of the zygote
occurs in the ___________.
a. seminiferous tubules; uterus
b. vagina; oviduct
c. oviduct; uterus
d. urethra; uterus
The correct answer is c—
A. Answer a is incorrect. Seminiferous tubules are found in males, not females.
The correct answer is c—
B. Answer b is incorrect. Fertilization does not occur in the vagina; it occurs in the
oviduct and implantation occurs in the uterus.
The correct answer is c—oviduct; uterus
C. Answer c is correct. Fertilization occurs in the oviduct, and implantation occurs in
the uterus.
The correct answer is c—
D. Answer d is incorrect. Fertilization does not occur in the urethra, which carries
urine, even though implantation does occur in the uterus.
13. Infertility—
a. occurs in females only
b. is always related to ovulation
c. is not known to be the result of sexually transmitted infections
d. all of these are false statements
The correct answer is d—
A. Answer a is incorrect. Infertility may occur in either sex.
The correct answer is d—
B. Answer b is incorrect. Infertility is only sometimes related to ovulation.
The correct answer is d—
C. Answer c is incorrect. Infertility can be caused by infection that is sexually
transmitted.
The correct answer is d—all of these are false statements
D. Answer d is correct. None of the other statements is correct.
14. An animal that is oviparous reproduces by—
a. giving birth to free-living young
b. producing internally fertilized eggs that develop externally
c. producing eggs that are fertilized externally
d. incubating eggs internally while the fetus develops
The correct answer is b—
A. Answer a is incorrect. The term oviparous means “egg-bearing,” which would not
apply to giving birth to free-living young.
The correct answer is b—producing internally fertilized eggs that develop externally
B. Answer b is correct. The term oviparous means “egg-bearing,” which would apply
to this example.
The correct answer is b—
C. Answer c is incorrect. The term oviparous is not applicable to this example.
The correct answer is b—
D. Answer d is incorrect. The term oviparous is not applicable to this example.
15. The testicles of male mammals are suspended in the scrotum because—
a. the optimum temperature for sperm production is less than the normal core
body temperature of the organism
b. the optimum temperature for sperm production is higher than the normal
core body temperature of the organism
c. there is not enough room in the pelvic area for the testicles to be housed
internally
d. it is easier for the body to expel sperm during ejaculation
The correct answer is a—the optimum temperature for sperm production is less than the
normal core body temperature of the organism
A. Answer a is correct. The molecules involved in sperm production are temperaturesensitive and work optimally at lower-than-normal body temperatures.
The correct answer is a—
B. Answer b is incorrect. Temperatures in the scrotum are lower than those within
the body.
The correct answer is a—
C. Answer c is incorrect. Space within the body is not an issue.
The correct answer is a—
D. Answer d is incorrect. The distance traveled by sperm is actually greater than it
would be from a more direct internal route.
Challenge Questions
1. Suppose that the SRY gene mutated such that a male embryo could not produce
functional protein. What kinds of changes would you expect to see in the
embryo?
Answer—A mutation that makes SRY nonfunctional would mean that the embryo would
lack the signal to form male structures during development. Therefore, the embryo
would have female genitalia at birth.
2. Why do you think that amphibians and many fish have external fertilization,
whereas lizards, birds, and mammals rely on internal fertilization?
Answer—Amphibians and fish that rely on external fertilization also have access to
water. Lizards, birds, and mammals have adaptations that allow them to reproduce away
from a watery environment. These adaptations include eggs that have protective shells or
internal development, or both.
3. How are the functions of FSH and LH similar in male and female mammals?
How do they differ?
Answer—FSH and LH are produced by the anterior pituitary in both males and females.
In both cases they play roles in the production of sex hormones and gametogenesis.
However, FSH stimulates spermatogenesis in males and oogenesis in females, whereas
LH promotes the production of testosterone in males and estradiol in females.
4. You are interested in developing a contraceptive that blocks hCG receptors. Will
it work? Why or why not?
Answer—It could indeed work. The hormone hCG is produced by the zygote to prevent
menstruation, which would in turn prevent implantation in the uterine lining. Blocking
the hormone receptors would prevent implantation and therefore pregnancy.
5. Why are all parthenogenic parents female?
Answer—Parthenogenic species reproduce from gametes that remain diploid. Sperm are
haploid, whereas eggs do not complete meiosis (becoming haploid) until after
fertilization. Therefore, only eggs could develop without DNA from an outside source.
In addition, only eggs have the cellular structures needed for development. Therefore
only females can undergo parthenogenesis.