Transcript 06 Animal Reproduction 2

Animal Reproduction
AP Biology
2005-2006
Sexual & asexual reproduction
 Asexual


offspring all have same genes (clones)
no variation
 Sexual


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gametes (sperm & egg)  fertilization
mixing of genes  variation
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Parthenogenesis
 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
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Different strokes…
gay
penguins
parthenogenesis in aphids
“lesbian” lizards
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sex-change in fish
Hermaphrodites
 Having functional
reproductive system
of both sexes
earthworms mating
flat worm
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Fertilization
 Joining of egg & sperm

external
 usually aquatic animals

internal
 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
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2005-2006
Reproductive hormones
 Testosterone


from testes
functions
LH &
FSH
 sperm production
 2° sexual
characteristics
 Estrogen


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 100 million produced per day!
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 ~2.5 million released per drop!

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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


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nutrient rich fluid to feed & protect sperm
buffer to counteract acids in vagina
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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
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
Female reproductive system
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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

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birth canal for birthing baby
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Female reproductive system
AP Biology
2005-2006
LH
Menstrual cycle
FSH
Hypothalamus
GnRH
egg development
ovulation = egg release
corpus luteum
Pituitary
FSH & LH
estrogen
progesterone
Ovaries
lining of uterus
estrogen
Body cells
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days 0
7
14
21
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28
Egg maturation in ovary
 Corpus luteum

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produces
progesterone
to maintain
uterine lining
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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



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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
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Oogenesis
 What is the advantage
of this development
system?
Meiosis 1 completed
during egg maturation
ovulation
Meiosis 2 completed
triggered by fertilization
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Fertilization
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Fertilization
 Joining of sperm & egg

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sperm head enters egg
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Cleavage
 Repeated mitotic divisions of zygote
1st step to becoming multicellular
 unequal divisions establishes body plan

 different cells receive different portions of egg
cytoplasm & therefore different regulatory signals
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Cleavage
 zygote  morula  blastula

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establishes future development
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Gastrulation
 Establish 3 cell layers

ectoderm
 outer layers
 skin, nails, teeth,
ectoderm
nerves

mesoderm
mesoderm
 blood, bone & muscle

endoderm
 inner lining
 digestive system
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endoderm
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Neurulation
 1st organ to form is notochord &
nerve chord

develop into nervous system
Neural groove
Neural tube
Notochord
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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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Human fetal development
4 weeks
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7 weeks
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Sex determination
Sperm
Ovum
Y
Zygote
XY
X
SRY
Indifferent
gonads
No SRY
X
Ovum
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X
Sperm
Develop in
early
embryo
Testes
XX
Zygote
Seminiferous
tubules
Leydig cells
Ovaries
(Follicles do not
develop until
third trimester)
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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
 The fetus just spends much of the 2nd &
3rd trimesters just growing
…and doing various flip-turns & kicks
inside amniotic fluid
Week 20
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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
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Birth (36 weeks)
Intestine
Placenta
Umbilical
cord
Wall of
uterus
Bladder
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Cervix
Vagina
Biology
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The end of the journey!
AP Biology
2005-2006