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Reproduction in the Animal Kingdom Sexual Asexual
FissionBuddingFragmentation & RegenerationParthenogenesis egg develops without
being fertilized
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
Reproductive Cycles and Patterns
Most animals exhibit cycles in reproductive activity Often related to changing seasons
Reproductive cycles Are controlled by hormones and
environmental cues
Fertilization Plays an important part in sexual
reproduction Joining of egg & sperm
external usually aquatic animals
internal usually land animals
Patterns of Sexual Reproduction
External fertilization, external development
Internal Fertilization, External Development
Internal Fertilization, Internal Development
Hermaphrodites
Certain Organisms seldom encounter a mate
Solution hermaphroditism In which each
individual has both male and female reproductive
Male Reproductive System Testicles
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
Male reproductive system Sperm production
over 100 million produced per day!
~2.5 million released per drop!
Testes & epididymis sperm production &
maturation Glands
seminal vesicles, prostate, bulbourethal
produce seminal fluid = nutrient-rich
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
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
Oogenesis
Meiosis 1 completed
during egg maturation
Meiosis 2 completedtriggered by
fertilization
ovulation
What is the advantage of this development system?
The reproductive cycle of the human female The Ovarian Cycle The Uterine (Menstrual) Cycle Menopause
Female Hormones FSH & LH
release from pituitary stimulates egg development & hormone release peak release = release of egg (ovulation)
Estrogen released from ovary cells around developing egg stimulates growth of lining of uterus lowered levels = menstruation
Progesterone released from “corpus luteum” in ovaries
cells that used to take care of developing egg stimulates blood supply to lining of uterus lowered levels = menstruation
The Ovarian Cycle In the ovarian cycle
Hormones stimulate follicle growth, which results in ovulation
Following ovulation The follicular tissue left behind
transforms into the corpus luteum
Figure 46.13a–e
Control by hypothalamus Inhibited by combination of estrogen and progesterone
Stimulated by high levelsof estrogen
Inhibited by low levels ofestrogen
Hypothalamus
Anterior pituitary
GnRH
FSH LH
Pituitary gonadotropinsin blood
LH
FSH
FSH and LH stimulatefollicle to grow
LH surge triggersovulation
Ovarian cycle
Growing follicle Maturefollicle
Corpusluteum
Degenerating corpus luteum
Estrogen secretedby growing follicle inincreasing amounts
Progesterone andestrogen secretedby corpus luteum
Follicular phase Luteal phaseOvulation
Ovarian hormonesin blood
Peak causes LH surge
Estrogen Progesterone
Estrogen levelvery low
Progesterone and estro-gen promote thickeningof endometrium
Uterine (menstrual) cycle
Endometrium
Menstrual flow phase Proliferative phase Secretory phase
0 5 10 14 15 20 25 28
Da
ys
1
(a)
(b)
(c)
(d)
(e)
3
6
7 8
4
5
2
10
9
The Uterine (Menstrual) Cycle
Occurs when the endometrium is shed Three Phases
Mentrual Flow Phase endometrium is shed and mentrual bleeding occurs
Proliferative Phase endometrium regenerates & thickens
Secretory Phaseendometrium thickens, if an embryo has not implanted by the end of this phaseA new menstrual flow commences
Menopause
After about 450 cycles, human females undergo menopause The cessation of ovulation and
menstruation
Placental Mammals Human Chorionic Gonadotropin
Secreted by embryo; acts like LH to maintain the Corpus Luteum
Excreted in urine Parturition
Birth; in late pregnancy; estrogen increases
This stimulates oxytocin receptorsOxytocin from fetus and mother
stimulate contractions
Hormonal Control of the Male Reproductive System
Testosterone and other androgens Are directly responsible for the primary
and secondary sex characteristics of the male
Androgen secretion and sperm production controlled by hypothalamic and pituitary hormones
Stimuli from otherareas in the brain
Hypothalamus
GnRH from thehypothalamus reg-ulates FSH and LH
release from theanterior pituitary.
FSH acts on theSertoli cells of the
seminiferoustubules, promotingspermatogenesis.
LH stimulates the Leydig cells to maketestosterone, whichin turn stimulatessperm production.
Anteriorpituitary
Negativefeedback
Leydig cellsmake
testosteronePrimary andsecondary sexcharacteristics
Sertoli cells
Spermatogenesis TestisFigure 46.14
Conception, Pregnancy and Birth
Blastocyst Implants by burrowing;
endometrium grows over
Provides nutrients first 2-4 weeks
Placenta Derived from both maternal and fetal cells produce progesterone Materials exchange across membranes
Human fetal development The fetus just spends much of the 2nd &
3rd trimesters just growing …and doing various flip-turns & kicks inside amniotic fluid
Week 20
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
Getting crowded in there!!
32 weeks (8 months)
The fetus sleeps 90-95% of the day & sometimes experiences REM sleep, an indication of dreaming
RU486
Progesterone analog Blocks progesterone receptors in
uterus; lining is shed Prostaglandins also taken