Chapter 46: Animal Reproduction
1. What are the 2 ways that animals reproduce?
- Asexual – mitosis – same genes as parent
- Fission – separation of a parent into 2 or individuals of the same size
- Budding – individuals split as an outgrowth from an existing one
- Some cnidarians
- Fragmentation – breaking of the body into several pieces followed by
regeneration
- Sponges, cnidarians, tunicates
- Sexual – fusion of haploid gametes
- Motile sperm swims to non-motile egg
- Increases genetic variability
2. What are the 2 types of sexual reproduction?
- External – eggs shed by female & fertilized by male in wet environment
- Courtship behaviors involved
- Pheromones used
- Internal - sperm deposited in or near female reproductive tract
& fertilized within female
- Fewer zygotes but more parental care
- Embryo develops in reproductive tract
Figure 46.5 External fertilization
Eggs
Chapter 46: Animal Reproduction
1. What are the 2 ways that animals reproduce?
2. What are the 2 types of sexual reproduction?
- External – eggs shed by female & fertilized by male in wet environment
- Courtship behaviors involved
- Pheromones used
- Internal - sperm deposited in or near female reproductive tract
& fertilized within female
- Fewer zygotes but more parental care
- Embryo develops in reproductive tract
3. What is parthenogenesis?
- Process in which an egg develops without fertilization
- Produces haploid adults that produce eggs without meiosis
- Daphnia (water flea), bees (male drones), wasps, ants
Figure 46.3 Sexual behavior in parthenogenetic lizards
Ovary
size
(a) Both lizards in this photograph are C. uniparens
females. The one on top is playing the role of
a male. Every two or three weeks during the
breeding season, individuals switch sex roles.
Ovulation
Hormones
Ovulation
Estrogen
Progesterone
Behavior
Time
Female- Malelike
like
Female- Malelike
like
(b) The sexual behavior of C. uniparens is correlated
with the cycle of ovulation mediated by sex hormones.
As blood levels of estrogen rise, the ovaries grow,
and the lizard behaves like a female. After ovulation,
the estrogen level drops abruptly, and the
progesterone level rises; these hormone levels
correlate with male behavior.
Chapter 46: Animal Reproduction
1.
2.
3.
4.
What are the 2 ways that animals reproduce?
What are the 2 types of sexual reproduction?
What is parthenogenesis?
What does the male reproductive tract look like?
Figure 46.10 Reproductive anatomy of the human male
(Urinary
bladder)
Seminal vesicle
(Rectum)
(Pubic bone)
Erectile
tissue of
penis
Vas deferens
Ejaculatory duct
Prostate gland
Bulbourethral gland
Urethra
Vas deferens Epididymis
Glans penis
Testis
Scrotum
External – scrotum & penis
Internal – gonads produce sperm & hormones
- testes – packed with highly coiled seminiferous tubules
- accessory glands that help sperm movement
- seminal vesicles
- bulbourethral glands
- prostate gland
Prepuce
Seminal
vesicle
(behind
bladder)
(Urinary
bladder)
Prostate gland
Urethra
Scrotum
Glans penis
Bulbourethral
gland
Erectile tissue
of penis
Vas deferens
Epididymis
Testis
5. Where do the sperm travel during ejaculation?
Propelled from epididymis  vas deferens  ejaculatory duct
6. How many sperm are released during ejaculation?
2 – 5 mL of semen per ejaculation
x 50 – 130 million sperm per mL
100 – 650 million sperm per ejaculation
7.
What happens after ejaculation?
Prostaglandins in semen thin mucus as the opening of the uterus &
stimulate uterine contractions which help semen move up uterus
Semen (slightly alkaline) neutralizes vagina (slightly acidic)
- Protects sperm & increases motility
Initially sperm are coagulated & become liquified so sperm can swim
8.
How does viagra work?
Promotes the action of nitric oxide (NO) which enhances relaxation of
smooth muscle in blood vessels of penis so blood can enter erectile
tissue
9. What does the female reproductive anatomy look like?
Figure 46.9 Reproductive anatomy of the human female
Uterus
Oviduct
(Urinary bladder)
(Pubic bone)
Ovary
(Rectum)
Cervix
Vagina
Urethra
Shaft
Prepuce Clitoris
Bartholin’s gland
Glans
Vaginal opening
Labia minora
Labia majora
External – clitoris & 2 sets of labia which surround the clitoris & vaginal opening
Internal – pair of gonads (ovaries) with ducts & chambers for gametes & fetus
Ovaries
Oviduct
Follicles
Uterus
Uterine wall
Endometrium
Corpus luteum
Cervix
Vagina
Ovaries – contain many follicles
- Follicle – all formed before birth
- egg cell surrounded by follicle cells which nourish & protect the egg
- produce estrogens
- Endometrium – inner lining of uterus
- After ovulation, “egg” falls down the oviduct into uterus
7.
What happens after ejaculation?
Prostaglandins in semen thin mucus as the opening of the uterus &
stimulate uterine contractions which help semen move up uterus
Semen (slightly alkaline) neutralizes vagina (slightly acidic)
- Protects sperm & increases motility
Initially sperm are coagulated & become liquified so sperm can swim
8.
How does viagra work?
Promotes the action of nitric oxide (NO) which enhances relaxation of
smooth muscle in blood vessels of penis so blood can enter erectile
tissue
9.
What does the female reproductive anatomy look like?
10. How are “eggs” made?
- Oogenesis
Figure 46.11 Human Oogenesis
Ovary
Primary germ cell in embryo
Differentiation
Oogonium
2n
Oogonium
in ovary
Mitotic
division
Primary oocyte,
arrested in prophase
of meiosis I
(present at birth)
2n
Completion of meiosis I
and onset of meiosis II
First
polar
body
n
n
Primary
oocyte
within
follicle
Growing
follicle
Secondary oocyte,
arrested at metaphase of meiosis II
Ovulation
n
n
Entry of
sperm triggers
completion of
meiosis II
Mature follicle
Second
polar
body
Ruptured
follicle
Ovum
Ovulated
secondary oocyte
Corpus luteum
Degenerating
corpus luteum
Follicles grow in response to FSH completing
meiosis I & stopping at metaphase II
Smaller polar body is discarded
Secondary oocyte is ovulated…NOT AN EGG
Meiosis is completed IF 2° oocyte is fertilized
After ovulation, remaining tissue reorganizes to
form the corpus luteum
7.
8.
9.
10.
11.
What happens after ejaculation?
Prostaglandins in semen thin mucus as the opening of the uterus &
stimulate uterine contractions which help semen move up uterus
Semen (slightly alkaline) neutralizes vagina (slightly acidic)
- Protects sperm & increases motility
Initially sperm are coagulated & become liquified so sperm can swim
How does viagra work?
Promotes the action of nitric oxide (NO) which enhances relaxation of
smooth muscle in blood vessels of penis so blood can enter erectile
tissue
What does the female reproductive anatomy look like?
How are “eggs” made?
Oogenesis
How are sperm made?
Spermatogenesis
Figure 46.12 Human Spermatogenesis
Epididymis
Seminiferous tubule
Testis
Cross section
of seminiferous
tubule
2n
Spermatogonium
Mitotic division,
producing large numbers
of spermatogonia
- Seminiferous tubules – produce sperm
- Leydig cells – secrete testosterone &
other androgens
- Sertoli cells – provide nutrition for
spermatids so they can mature
- Takes 65 – 75 days to make sperm
- 20 days to travel epididymis where
they mature & are stored
Sertoli cell
nucleus
Differentiation and
Onset of meiosis I
Primary spermatocyte
(in prophase of meiosis I)
2n
Meiosis I completed
n
n
Secondary spermatocyte
Meiosis II
n
n
n
n
Early
spermatids
Lumen of
Seminiferous tubule
Spermatids
(at two stages of
differentiation)
Differentiation
(Sertoli cells provide
nutrients)
n
n
n
n
Sperm cells
Neck
Head Midpiece
Mitochondria
Nucleus
Acrosome
Tail
Plasma membrane
7.
8.
9.
10.
11.
12.
13.
What happens after ejaculation?
Prostaglandins in semen thin mucus as the opening of the uterus &
stimulate uterine contractions which help semen move up uterus
Semen (slightly alkaline) neutralizes vagina (slightly acidic)
- Protects sperm & increases motility
Initially sperm are coagulated & become liquified so sperm can swim
How does viagra work?
Promotes the action of nitric oxide (NO) which enhances relaxation of
smooth muscle in blood vessels of penis so blood can enter erectile
tissue
What does the female reproductive anatomy look like?
How are “eggs” made?
Oogenesis
How are sperm made?
Spermatogenesis
What are the differences between spermatogenesis & oogenesis?
Unequal cytokinesis in oogenesis produces 1 haploid ovum (& 2 polar
bodies) & not 4 haploid sperm
Spermatogenesis mitosis occurs throughout life but ovary has all its
follicles at birth
Oogenesis has long resting periods but spermatogenesis is
uninterrupted & continuous
How do hormones control the menstrual cycle?
Figure 46.13 The reproductive cycle of the human female
GnRH – Gonadotropin Releasing Hormone
Stimulated by high levels
1
GnRH
of estrogen
- hypothalamus
Anterior pituitary
Inhibited by low levels of
estrogen
- stimulates release of FSH & LH
LH
FSH
2
by anterior pituitary
(b) Pituitary gonadotropins
6
in blood
FSH
- Follicle Stimulating Hormone
- follicle grows & expresses LH receptors
LH
LH
- Lutenizing Hormone
FSH
- triggers ovulation (1 day after LH peak)
3 FSH and LH stimulate LH surge triggers
follicle to grow
ovulation
(c) Ovarian cycle
7
8
- stimulates formation of corpus luteum
Estrogen – produced by growing follicle
Corpus Degenerating
Growing follicle Mature
luteum corpus luteum
follicle
- stimulates GnRH release which triggers
Ovulation
Luteal phase
Follicular phase
Progesterone and
Estrogen secreted
more LH & FSH
4
estrogen secreted
by growing follicle in
by corpus luteum
increasing amounts
- estrogen peak causes LH peak
Peak causes
(d) Ovarian hormones
5
LH
surge
in blood
Progesterone – from corpus luteum
10
Progesterone
Estrogen
9
- maintains thick endometrium in
Progesterone and estroEstrogen level
preparation for embryo implant
gen promote thickening
very low
of endometrium
If pregnancy does not occur the endometrium is
(e) Uterine (menstrual) cycle
shed….menstruation.
Endometrium
Menopause – cessation of ovulation & menstruation because ovaries lose responsiveSecretory phase
Menstrual flow phase Proliferative phase
ness to LH & FSH & estrogen decreases
25
28
5
14
15
0
20
10
(a)
Control by hypothalamus
ays
Hypothalamus
Inhibited by combination of
estrogen and progesterone
7.
What happens after ejaculation?
8.
How does viagra work?
9.
What does the female reproductive anatomy look like?
10. How are “eggs” made?
11. How are sperm made?
12. What are the differences between spermatogenesis & oogenesis?
13. How do hormones control the menstrual cycle?
14. How do hormones control the male reproductive system?
- GnRH, FSH, & LH
Figure 46.14 Hormonal control of the testes
Stimuli from other
areas in the brain
Hypothalamus
GnRH from the
hypothalamus regulates FSH and LH
release from the
anterior pituitary.
Anterior
pituitary
Negative
feedback
FSH acts on the
Sertoli cells of the
seminiferous
tubules, promoting
spermatogenesis.
LH stimulates the
Leydig cells to make
testosterone, which
in turn stimulates
sperm production.
Leydig cells
make
testosterone
Sertoli cells
Spermatogenesis
Primary and
secondary sex
characteristics
Testis
7.
What happens after ejaculation?
8.
How does viagra work?
9.
What does the female reproductive anatomy look like?
10. How are “eggs” made?
11. How are sperm made?
12. What are the differences between spermatogenesis & oogenesis?
13. How do hormones control the menstrual cycle?
14. How do hormones control the male reproductive system?
- GnRH, FSH, & LH
15.
What is detected in pregnancy tests?
HCG – human chorionic gonadotropin
Mimics LH which keeps corpus luteum secreting estrogen &
progesterone
Endometrium stays thick
16. What happens after fertilization?
Fig 46.15 Formation of the zygote and early post-fertilization events
3 Cleavage (cell division)
begins in the oviduct
as the embryo is moved
toward the uterus
by peristalsis and the
movements of cilia.
4 Cleavage continues.
By the time the embryo
reaches the uterus,
it is a ball of cells.
It floats in the uterus for
several days, nourished by
endometrial secretions. It
becomes a blastocyst.
Ovary
2 Fertilization occurs. A sperm
enters the oocyte; meiosis of
the oocyte finishes; and the
nuclei of the ovum and sperm
fuse, producing a zygote.
5 The blastocyst implants
in the endometrium
about 7 days after conception.
Uterus
1 Ovulation releases a
secondary oocyte, which
enters the oviduct.
(a) From ovulation to implantation
Endometrium
Endometrium
Inner cell mass
Cavity
Blastocyst
Trophoblast
(b) Implantation of blastocyst
Inner cell mass – develops into embryo & extra-embryonic membranes
Trophoblast – outer layer of blastocyst that grows out & mingles with endometrium &
helps form the placenta
Placenta – disk shaped organ containing embryonic & maternal blood vessels
Figure 46.16 Placental circulation
Maternal
arteries
Maternal
veins
Placenta
Maternal portion
of placenta
Umbilical cord
Chorionic villus
containing fetal
capillaries
Fetal portion of
placenta (chorion)
Maternal blood
pools
Uterus
Fetal arteriole
Fetal venule
Umbilical cord
Umbilical arteries
Umbilical vein
As placenta forms, HCG levels decline & placenta secretes its own progesterone
Fetal nutrients gained from maternal blood pools….no mixing of blood.
7.
What happens after ejaculation?
8.
How does viagra work?
9.
What does the female reproductive anatomy look like?
10. How are “eggs” made?
11. How are sperm made?
12. What are the differences between spermatogenesis & oogenesis?
13. How do hormones control the menstrual cycle?
14. How do hormones control the male reproductive system?
- GnRH, FSH, & LH
15.
What is detected in pregnancy tests?
HCG – human chorionic gonadotropin
Mimics LH which keeps corpus luteum secreting estrogen &
progesterone
Endometrium stays thick
16. What happens after fertilization?
17. How do hormones regulate parturition, aka child birth?
Figure 46.18 A model for the induction of labor
from
ovaries
Oxytocin
from fetus
and mother's
posterior pituitary
Induces oxytocin
receptors on uterus
Stimulates uterus
to contract
Stimulates
placenta to make
Prostaglandins
Stimulate more
contractions
of uterus
Positive feedback
Estrogen
Figure 46.19 The three stages of labor
Placenta
Umbilical
cord
Uterus
Cervix
1 Dilation of the cervix
2 Expulsion: delivery of the infant
Uterus
Placenta
(detaching)
Umbilical
cord
3 Delivery of the placenta
7.
What happens after ejaculation?
8.
How does viagra work?
9.
What does the female reproductive anatomy look like?
10. How are “eggs” made?
11. How are sperm made?
12. What are the differences between spermatogenesis & oogenesis?
13. How do hormones control the menstrual cycle?
14. How do hormones control the male reproductive system?
- GnRH, FSH, & LH
15.
What is detected in pregnancy tests?
HCG – human chorionic gonadotropin
Mimics LH which keeps corpus luteum secreting estrogen &
progesterone
Endometrium stays thick
16. What happens after fertilization?
17. How do hormones regulate parturition, aka child birth?
18. How does contraception work?
Figure 46.20 Mechanisms of some contraceptive methods
Female
Male
Method
Event
Event
Method
Production of Production of
viable sperm viable oocytes
Vasectomy
Sperm transport Ovulation
down male
duct system
Abstinence
Combination
birth control
pill (or injection,
patch, or
vaginal ring)
Abstinence
Birth control pills – estrogen & progesterone combo
- prevents ovulation by decreasing the release
of GnRH which inhibits FSH & LH
Condom
Coitus
interruptus
(very high
failure rate)
Sperm Capture of the
deposited oocyte by the
in vagina
oviduct
Tubal ligation
Transport
Sperm
movement of oocyte in
oviduct
through
female
reproductive
tract
Spermicides;
diaphragm;
cervical cap;
progestin alone
(minipill, implant,
or injection)
Meeting of sperm and oocyte
in oviduct
Union of sperm and egg
Morning-after
pill (MAP)
Progestin alone
Implantation of blastocyst
in properly prepared
endometrium
Birth
Morning after pill – higher doses of estrogen & progesterone
- prevents fertilization or implantation