Transcript Animal Reproduction & Development

Animal Reproduction
&
Development
2007-2008
Sexual & asexual reproduction

Asexual




offspring all have same genes (clones)
Little to no variation
Fragmentation and budding
Sexual


gametes (sperm & egg)  fertilization
mixing of genes  variation
4/4/2016
Parthenogenesis


Egg development without a male contribution
Wasps, honeybees, aphids, komodo dragons, some
fish, frogs and lizards
 Usually
produces males
4/4/2016
Mechanisms of sexual reproduction

Fertilization(union of sperm and egg)


external
internal
 Timing
 Compatible
copulatory
organs
 All species produce more
offspring than the
environment can handle
 Survival???

Pheromones

chemical signals that influence the
behavior of others (mate attractants)
4/4/2016
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
testes
or
ovaries
4/4/2016
Sex hormone control in males
Hypothalamus
GnRH
Pituitary
FSH & LH
Testes
testosterone
Body cells
4/4/2016
Testicle
(seminiferous
tubules)
Male reproductive
system
sperm
spermatocytes

Testes & epididymis



sperm production & maturation
Sperm production

over 100 million produced per
day!

~2.5 million released per drop!
Glands

seminal vesicles, prostate,
bulbourethal

produce seminal fluid =
nutrient-rich (sugars)
Spermatogenesis
Epididymis
Produce semen by age 7
Produce sperm by puberty (11-14
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
4/4/2016
Female
reproductiv
e system
4/4/2016
Female reproductive system

Ovaries


Uterus


tubes for eggs to travel from ovaries to uterus
Cervix


nurtures fetus; lining builds up each month
Fallopian tubes


produces eggs & hormones
opening to uterus, dilates 10cm (4 inches) for birthing
baby
Vagina

birth canal for birthing baby
4/4/2016
Menstrual
cycle
LH
FSH
Hypothalamus
GnRH
egg development
ovulation = egg release
corpus luteum
Pituitary
FSH & LH
estrogen
progesterone
Ovaries
lining of uterus
estrogen
Body cells
4/4/2016
days 0
7
14
21
28
Female hormones

FSH & LH




Estrogen




release from pituitary
stimulates egg development (follicle) & hormone release
peak release = release of egg (ovulation)
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
4/4/2016
Egg maturation in ovary

Corpus luteum

produces
progesterone
to maintain
uterine lining
4/4/2016
release
Oogenesis

Unequal meiotic divisions



unequal distribution
of cytoplasm
1 egg
2 polar bodies
Cell stored in
ovaries
Meiosis 1 completed
during egg maturation
Cell matures
in follicle on
ovary
Meiosis 2 completed
triggered by fertilization
ovulation
Fertilization

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


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


fertilization
Cleavage
Morula
Blastocyst
Implantation
gastrulation
neurulation
Organogenesis
Fetus
Fertilization

Joining of sperm & egg
 sperm
head (nucleus) enters egg
 Acrosome (enzyme filled vesicle)
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
Cleavage

zygote  morula  blastula
 establishes
future development
zygote
gastrulation
morula
blastula
Gastrulation

gastrulation in
primitive chordates
Establish 3 cell layers

ectoderm
 outer



body tissues
skin, nails, teeth
nerves, eyes, lining of mouth
mesoderm
 middle



ectoderm
tissues
blood & lymph, bone & notochord, muscle
excretory & reproductive systems
mesoderm
endoderm
 inner


lining
digestive system
lining of respiratory, excretory &
reproductive systems
endoderm
Neurulation

Formation of notochord & neural tube
 develop
into nervous system
Neural tube
Notochord
develops into
vertebral column
develops into CNS
(brain & spinal cord)
Organogenesis

Organ development and differentiation from germ
layers
Placenta

Materials exchange across membranes
Human fetal development
4 weeks
7 weeks
Human fetal development
10 weeks
Human fetal development
12 weeks
20 weeks
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
Human fetal development

30 weeks (7.5 months)
umbilical cord
Getting crowded in there!!

32 weeks (8 months)
The fetus sleeps 9095% of the day &
sometimes experiences
REM sleep, an indication
of dreaming
Fetal slide notes
Apoptosis

Programmed cell death
 Sculpts
body parts
 Genetically programmed elimination of tissues & cells that
were used for only short periods in embryo or adult
 human
embryos develop with webs between toes & fingers, but
they are not born that way!
2004-2005
positive feedback
Birth
Birth (36 weeks)
Intestine
Placenta
Umbilical
cord
Wall of
uterus
Bladder
Cervix
Vagina