Animal Reproduction Chapter 46 Rick L. Knowles Liberty Senior High School A.P. Biology.
AP Biology 2005-2006 Animal Reproduction Chapter 46.
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Transcript of AP Biology 2005-2006 Animal Reproduction Chapter 46.
AP Biology 2005-2006
Animal Reproduction
Chapter 46
AP Biology 2005-2006
Sexual & asexual reproduction Asexual
offspring all have same genes (clones) no variation
Sexual gametes (sperm & egg) fertilization mixing of genes variation
AP Biology
Parthenogenesis Development of an unfertilized egg
honey bees drones = males produced through
parthenogenesis haploid workers & queens = females produced from
fertilized eggs diploid
queen worker drone
AP Biology 2005-2006
Different strokes…
parthenogenesis in aphids
sex-change in fish
AP Biology
Hermaphrodites
flat worm
earthworms mating
Having functional reproductive system of both sexes
AP Biology 2005-2006
Fertilization Joining of egg & sperm
external usually aquatic animals
internal 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 live birth
AP Biology 2005-2006
Adaptive advantages? What is the adaptive value of each
type of sexual reproduction number of eggs? level of parental care habitat?
AP Biology 2005-2006
Human Reproduction: Reproductive hormones Testosterone
from testes Functions
Prenatal development of male genitalia
sperm production 2° sexual characteristics Maintenance of sex
drive Estrogen
from ovaries functions
egg production prepare uterus for
fertilized egg 2° sexual characteristics
LH &FSH
testesor
ovaries
AP Biology 2005-2006
Sex hormone control in males
Hypothalamus
Pituitary
Testes
Body cells
GnRH
FSH & LH
testosterone
AP Biology 2005-2006
Sperm production over 100 million produced per day! ~2.5 million released per drop!
Male reproductive system
AP Biology
Male reproductive system Testes
produces sperm & hormones Scrotum
sac that holds testicles outside of body Epididymis
where sperm mature Vas deferens
tubes for sperm to travel from testes to penis Prostate, seminal vesicles,
Cowper’s (bulbourethal) glands nutrient rich fluid to feed & protect sperm buffer to counteract acids in vagina
AP Biology 2005-2006
Male reproductive system
Testes & epididymis sperm production &
maturation
Glands seminal vesicles,
prostate, bulbourethal produce seminal fluid =
nutrient-rich
seminiferous tubule
sperm
spermatocytes
AP Biology
Spermatogenesis Spermatogenesis
occurs within each testis in small tubules called seminiferous tubules
This light micrograph shows a cross section of seminiferous tubules, blood vessels and the
interstitial Leydig cells.Leydig cells are responsible for the production of testosterone.
AP Biology
Spermatogenesis Mitosis and meiosis
may be taking place at any time in the spermatogonia. Mitosis replenishes numbers of cells, meiosis produces actual sperm (spermatozoa)
Sertoli cells help nourish sperm cells during meiosis
AP Biology 2005-2006
SpermatogenesisEpididymis Testis
Coiledseminiferoustubules
Vas deferens
Cross-section ofseminiferous tubule
Spermatozoa
Spermatids(haploid)
2°spermatocytes
(haploid)
1°spermatocyte
(diploid)
Germ cell (diploid)
MEIOSIS II
MEIOSIS I
AP Biology
Hormonal control of sperm production
LH (Leutinizing hormone) stimulates Leydig cells to produce testosterone
FSH (follicle-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 stored briefly in the epididymis.
On sexual arousal, millions of sperm cells are moved from the epididymis into the vas deferens.
Seminal vesicles 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 prostrate adds more fluid: alkalinewhich helps the sperm survive the acidicenvironment 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 Fallopian tubes
tubes for eggs to travel from ovaries to uterus
Cervix opening to uterus, dilates 10cm (4 inches)
for birthing baby Vagina
birth canal for birthing baby
AP Biology
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 (endometrium)
•The implantation must occur when the endometrium is rich with blood vessels.
•The breakdown of the blood vessels leads to menstrual bleeding (menstruation); a sign that no pregnancy has occurred
AP Biology
Hormones
Hypothalamus
Pituitary
Ovaries
Endometrium of uterus
GnRH
FSH & LH
estrogen progesterone
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.
The target tissues for these 2 hormones are the ovaries
AP Biology
Effects of FSH and LH on the ovaries To increase the production and secretion of estrogen
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 2005-2006
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 corpus luteum. The corpus luteum produces progesterone for 10-12 days after ovulation.
Progesterone (hormone) maintains the thickened endometrium
If no pregnancy, the corpus luteum eventually breaks down = less estrogen and
progesterone
AP Biology
LH
FSH
egg development ovulation = egg release
corpus luteum
estrogen
progesterone
lining of uterus
days 0 7 14 21 28
Menstrual cycle
… as estrogen and progesterone levels fall, the highly vascular endometrium can no longer be maintained. The capillaries begin to rupture and menstruation begins.
The drop in progesterone and estrogen also signals the hypothalamus to begin secreting GnRH and another menstrual cycle begins.
AP Biology 2005-2006
Oogenesis
Meiosis 2 completedtriggered by fertilization
ovulation
In ovaries, cells called oogonia 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 FSH periodically stimulates a follicle to grow and induces its primary oocyte to complete meiosis I and start meiosis II
AP Biology
Comparison of spermatogenesis and oogenesis
Millions of sperm 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
One egg is ovulated per 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
Spermatogenesis Oogenesis
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Fertilization
AP Biology 2005-2006
Fertilization Enzymes from acrosome are released at the zona pellucida.
Sperm head enters egg, plasma membranes fuse together. This initiates the cortical reaction.
AP Biology
Fertilization and the cortical reaction
As soon as the sperm reaches the nucleus, the cortical granules fuse with the cell membrane and release their enzymes to the outside, making it impermeable to any other sperm cells.
AP Biology 2005-2006
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 blastocyst.
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 HCG. This hormone maintains production of progesterone from the ovary, a crucial factor in maintaining a pregnancy.
AP Biology
HCG specifics HCG = Human Chorionic Gonadotrophin. It enters the bloodstream of the mother its target tissue is the corpus luteum. 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 placenta will take over estrogen and progesterone production.
AP Biology
OrganogenesisUmbilical blood vessels
Chorion
Amnion
Yolksac
AllantoisFetal blood vessels
Maternal blood vessels
Bird embryo
Mammalian embryo
Placenta
AP Biology 2005-2006
Placenta Materials exchange across membranes
AP Biology
Role of the PlacentaWhen fully formed, 2 fetal blood
vessels within the umbilical cord carry fetal blood to the placenta. The blood is deoxygenated and carries waste products (CO2, 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 nutrients, 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 Amniotic sac 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 temperature stability
AP Biology 2005-2006
Human fetal development
7 weeks4 weeks
AP Biology 2005-2006
Human fetal development10 weeks
AP Biology 2005-2006
Human fetal development
12 weeks 20 weeks
AP Biology 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
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Birth
Hormone induction
positive feedback
AP Biology 2005-2006
Intestine
Placenta
Umbilicalcord
Wall ofuterus
VaginaCervix
Birth (36 weeks)
Bladder
AP Biology
The end of the journey!