Transcript Chapter 46.

Chapter 46
Animal Reproduction
AP Biology
2005-2006
Sexual & asexual reproduction
 Asexual


offspring all have same genes (clones)
______________
 Sexual


AP Biology
gametes (sperm & egg)  fertilization
mixing of genes  ___________
2005-2006
___________________
 Development of an unfertilized egg

honey bees
 drones = males produced through
parthenogenesis  haploid
 workers & queens = females produced from
fertilized eggs  diploid
AP Biology
queen
worker
drone
Different strokes…
parthenogenesis in aphids
AP Biology
2005-2006
sex-change in fish
________________
 Having functional
reproductive system
of both sexes
earthworms mating
flat worm
AP Biology
Fertilization
 Joining of egg & sperm

_____________
 usually aquatic animals

_____________
 usually land animals
AP Biology
2005-2006
Development
 External


development in eggs
fish & amphibians in water
 soft eggs= exchange across membrane

birds & reptiles on land
 hard-shell amniotic eggs
 structures for exchange of food, O2 & waste

sharks & some snakes
 live births from eggs
 Internal

placenta
 exchange food & waste

AP Biology
live birth
2005-2006
Adaptive advantages?
 What is the adaptive value of each
type of sexual reproduction
number of eggs?
 level of parental of care
 habitat?

AP Biology
2005-2006
Human Reproduction: Reproductive hormones
 ___________________


from testes
Functions
LH &
FSH
 Prenatal development of
male genitalia
 sperm production
 2° sexual characteristics
 Maintenance of sex
drive
 _______________


from ovaries
functions
 egg production
 prepare uterus for
fertilized egg
 2° sexual characteristics
AP Biology
testes
or
ovaries
2005-2006
Sex hormone control in males
Hypothalamus
GnRH
Pituitary
FSH & LH
Testes
testosterone
Body cells
AP Biology
2005-2006
Male
reproductive
system
 Sperm production
over ____________ produced per day!
AP Biology
2005-2006
 ~2.5 million released per drop!

Male reproductive system
 Testes

produces sperm & hormones
 _____________

sac that holds testicles outside of body
 Epididymis

where sperm mature
 ______________

tubes for sperm to travel from testes to penis
 Prostate, seminal vesicles,
Cowper’s (bulbourethal) glands


AP Biology
nutrient rich fluid to feed & protect sperm
buffer to counteract acids in vagina
seminiferous tubule
Male reproductive system
sperm
spermatocytes
 Testes & epididymis

sperm production &
maturation
 Glands

AP Biology
seminal vesicles,
prostate, bulbourethal
 produce seminal fluid =
2005-2006
nutrient-rich
Spermatogenesis
 Spermatogenesis
occurs within each
testis in small
tubules called
_________________
_________________
AP Biology
This light micrograph shows a
cross section of seminiferous
tubules, blood vessels and the
interstitial _______________.
Leydig cells are responsible for
the production of testosterone.
Spermatogenesis
Mitosis and meiosis
may be taking
place at any time in
the spermatogonia.
Mitosis
replenishes
numbers of cells,
meiosis produces
actual sperm
(spermatozoa)
____________ help
nourish sperm
cells during
meiosis
AP Biology
Spermatogenesis
Epididymis
Testis
Coiled
seminiferous
tubules
Germ cell
(diploid)
1°
spermatocyte
(diploid)
MEIOSIS I
2°
spermatocytes
(haploid)
MEIOSIS II
Vas deferens
Spermatids
(haploid)
Spermatozoa
Cross-section of
seminiferous tubule
AP Biology
2005-2006
Hormonal control of sperm production
 LH (_______________
hormone) stimulates
Leydig cells to
produce testosterone
 FSH (___________ stimulating hormone)
and testosterone
stimulate meiosis in
spermatogonia to
produce spermatozoa
AP Biology
Role of epididymis, seminal vesicles,
and prostate in semen production
Sperm cells were produced in seminiferous tubules, carried
thru the lumen, and sent to the epididymis. They are _______
briefly in the epididymis.
On sexual arousal, millions of sperm cells are moved from the
epididymis into the ________________.
_________________ add large volume of fluid which has a high
conc. of fructose for energy for the sperm cells to swim
(approx. 70% of the fluid in
semen is added by the seminal
vesicles.)
The _________ adds more fluid: alkaline
which helps the sperm survive the acidic
environment in a female’s vagina.
AP Biology
Female reproductive system
AP Biology
Female reproductive system
 Ovaries

produces eggs & hormones
 Uterus

nurtures fetus; lining builds up each month
 ______________________

tubes for eggs to travel from ovaries to
uterus
 _____________

opening to uterus, dilates 10cm (4 inches)
for birthing baby
 Vagina

AP Biology
birth canal for birthing baby
Female reproductive system
AP Biology
Menstrual cycle
 Starting at puberty, human females

begin a hormonal cycle called the
menstrual cycle. Each cycle lasts (on
average) 28 days.
The purpose is to time the release of
an egg (ovum) for possible
fertilization and later implantation
into the inner lining of the uterus
(____________________)
•The implantation must occur when the endometrium is rich
with blood vessels.
•The breakdown of the blood vessels leads to menstrual
bleeding (________________); a sign that no pregnancy
has occurred
AP Biology
Hormones
Hypothalamus
Pituitary
FSH & LH
regulatory center for the menstrual
cycle.
The hypothalamus produces a
hormone called GnRH
(gonadotrophin-releasing
hormone).
The target tissue of GnRH is the
anterior pituitary gland, which
results in the pituitary producing
and secreting 2 hormones into the
bloodstream:
FSH and LH.
estrogen progesterone
Endometrium
of uterus
AP Biology
The target tissues for these 2
hormones are the ovaries
Effects of FSH and LH on the ovaries
 To increase the production and secretion of

__________ by the follicle cells of the ovary
 Estrogen enters the bloodstream
 Its target tissue is the endometrium of the uterus
 Result is growth of lining (increase in blood
vessels)
Stimulates egg development in ovaries
AP Biology
Egg maturation in ovary
 A spike in levels of FSH
and LH leads to ovulation
(release of oocyte from the
follicle)
 The outer ring of follicle
cells begin to divide and fill
in the ‘wound’ area left by
ovulation which forms a
____________. The corpus
luteum produces
progesterone for 10-12
days after ovulation.
 Progesterone (hormone)
___________ the thickened
endometrium
 If no pregnancy, the corpus
luteum eventually breaks
down = less estrogen and
AP Biology
progesterone
2005-2006
LH
Menstrual cycle
FSH
… as estrogen and
progesterone levels fall,
egg development ovulation = egg release
the highly vascular
endometrium can no
longer be maintained.
corpus luteum
The capillaries begin to
rupture and
menstruation begins.
estrogen
The drop in progesterone
progesterone
and estrogen also
signals the
lining of uterus
_____________ to begin
secreting GnRH and
another menstrual cycle
begins.
AP Biology
days 0
7
14
21
28
Oogenesis
In ovaries, cells called ________ go thru
mitosis repeatedly to build up numbers
of cells. Then those oogonia grow into
larger cells (primary oocytes) and start
meiosis, but the process stops at
Prophase I, until puberty.
Then ____ periodically stimulates
a follicle to grow and induces its
primary oocyte to complete
meiosis I and start meiosis II
ovulation
Meiosis 2 completed
triggered by fertilization
AP Biology
2005-2006
Comparison of spermatogenesis and oogenesis
Spermatogenesis
Oogenesis
 Millions of sperm
 One egg is ovulated per







produced every day
4 gametes for every cell
that begins meiosis
Very small
Occurs in testis
Released during
ejaculation
Haploid nuclei
Continues throughout all
of life, starting at puberty
AP Biology





menstrual cycle
One gamete is produced
for each cell that begins
meiosis (plus polar bodies)
Eggs are ‘large’
Occurs in ovaries
Released during ovulation
Haploid nuclei
Ovulation starts at puberty,
occurs with each
menstrual cycle, then
stops at menopause
Fertilization
AP Biology
Fertilization
Enzymes from acrosome are released at the _____________.
Sperm head enters egg, plasma membranes fuse
together. This initiates the ___________________.
AP Biology
2005-2006
Fertilization and the cortical reaction
As soon as the sperm reaches the nucleus, the ________________ fuse
with the cell membrane and release their enzymes to the outside,
making it impermeable to any other sperm cells.
AP Biology
Early human embryonic development:
Cleavage
 Fertilization triggers the zygote to start repeated
mitotic divisions as it moves down the Fallopian
tube toward the uterus
 By the time the embryo reaches the uterus, it is
approx. 100 cells and is ready to implant into the
endometrium of the uterus. At this point, it’s a
hollow ball of cells called a ________________.
AP Biology
2005-2006
AP Biology
A few days later, the embryo imbeds
itself in the uterine lining. At this
point, a woman's body begins to
secrete a pregnancy hormone known
as _______. This hormone maintains
production of progesterone from the
ovary, a crucial factor in maintaining a
pregnancy.
HCG specifics
 HCG = Human ____________ Gonadotrophin.
 It enters the bloodstream of the mother
 its target tissue is the ______________. HCG
acts to maintain the secretory functions of
this gland beyond the length of time typical of
a normal menstrual cycle. The corpus luteum
continues to make both estrogen and
progesterone and the endometrium is
maintained.
 Later on in pregnancy, the ________ will take
over estrogen and progesterone production.
AP Biology
Organogenesis
Mammalian embryo
Umbilical blood vessels
Chorion
Bird embryo
Amnion
Yolk
sac
Allantois
Fetal blood vessels
Placenta
AP Biology
Maternal blood vessels
2005-2006
Placenta
 Materials exchange across membranes
AP Biology
2005-2006
Role of the Placenta
When fully formed, 2 fetal blood
vessels within the umbilical cord
carry fetal blood to the placenta.
The blood is ________________ and
carries waste products (_____, urea,
hormones). This fetal blood
exchanges materials (not blood)
with the maternal bloodstream.
Another fetal blood vessel returns the
‘clean’ blood to the fetus (has
oxygen and __________, hormones)
At no time do the 2 bloods actually mix
When the corpus luteum stops
producing estrogen and
progesterone, the placenta starts
producing and secreting them.
AP Biology
Role of the amniotic fluid
 _____________ extends all
the way around the fetus
 The fluid within it is called
amniotic fluid
 Several functions:

Provides cushioning effect if
something happens to
mom’s abdomen
•Provides safe environment where fetus has free
movement and can exercise its developing muscles
and skeleton
•Provides ______________ stability
AP Biology
Human fetal development
4 weeks
AP Biology
7 weeks
2005-2006
Human fetal development
10 weeks
AP Biology
2005-2006
Human fetal development
12
weeks
AP Biology
20 weeks
2005-2006
Human fetal development
 24 weeks (6 months; 2nd trimester)
fetus is covered
with fine, downy
hair called
lanugo. Its skin
is protected by
a waxy material
called vernix
AP Biology
2005-2006
Human fetal development
 30 weeks (7.5 months)
umbilical cord
AP Biology
2005-2006
Getting crowded in there!!
 32 weeks (8 months)
The fetus
sleeps 90-95%
of the day &
sometimes
experiences
REM sleep, an
indication of
dreaming
AP Biology
2005-2006
Hormone
induction
positive feedback
AP Biology
Birth
Birth (36 weeks)
Intestine
Placenta
Umbilical
cord
Wall of
uterus
Bladder
AP
Cervix
Vagina
Biology
2005-2006
The end of the journey!
AP Biology