Transcript Chapter 46.
Chapter 46
Animal Reproduction
AP Biology
2005-2006
Sexual & asexual reproduction
Asexual
offspring all have same genes (clones)
______________
Sexual
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gametes (sperm & egg) fertilization
mixing of genes ___________
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___________________
Development of an unfertilized egg
honey bees
drones = males produced through
parthenogenesis haploid
workers & queens = females produced from
fertilized eggs diploid
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queen
worker
drone
Different strokes…
parthenogenesis in aphids
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sex-change in fish
________________
Having functional
reproductive system
of both sexes
earthworms mating
flat worm
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Fertilization
Joining of egg & sperm
_____________
usually aquatic animals
_____________
usually land animals
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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
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live birth
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Adaptive advantages?
What is the adaptive value of each
type of sexual reproduction
number of eggs?
level of parental of care
habitat?
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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
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testes
or
ovaries
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Sex hormone control in males
Hypothalamus
GnRH
Pituitary
FSH & LH
Testes
testosterone
Body cells
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Male
reproductive
system
Sperm production
over ____________ produced per day!
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~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
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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
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seminal vesicles,
prostate, bulbourethal
produce seminal fluid =
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nutrient-rich
Spermatogenesis
Spermatogenesis
occurs within each
testis in small
tubules called
_________________
_________________
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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
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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
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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
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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.
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Female reproductive system
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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
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birth canal for birthing baby
Female reproductive system
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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
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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
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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
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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
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progesterone
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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.
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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
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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
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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
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Fertilization
Enzymes from acrosome are released at the _____________.
Sperm head enters egg, plasma membranes fuse
together. This initiates the ___________________.
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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.
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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 ________________.
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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.
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Organogenesis
Mammalian embryo
Umbilical blood vessels
Chorion
Bird embryo
Amnion
Yolk
sac
Allantois
Fetal blood vessels
Placenta
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Maternal blood vessels
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Placenta
Materials exchange across membranes
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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.
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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
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Human fetal development
4 weeks
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7 weeks
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Human fetal development
10 weeks
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Human fetal development
12
weeks
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20 weeks
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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
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Human fetal development
30 weeks (7.5 months)
umbilical cord
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Getting crowded in there!!
32 weeks (8 months)
The fetus
sleeps 90-95%
of the day &
sometimes
experiences
REM sleep, an
indication of
dreaming
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Hormone
induction
positive feedback
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Birth
Birth (36 weeks)
Intestine
Placenta
Umbilical
cord
Wall of
uterus
Bladder
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Cervix
Vagina
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The end of the journey!
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