1. Great diversity of reproductive structures
Reproduction
Reading: Chapter 10; pp
Great diversity of reproductive structures
Great diversity of reproductive strategies
-timing
-number of young
-how developed young are when born
-many others

2. Eggs much larger than in
Monotremes:
-single common opening from urinary and reproductive tracts
called a cloaca (just like lower vertebrates and birds)
-Only left ovary is functional
-Have mammary glands,
but no nipples
Eggs much larger than in
viviparous mammals
-much more yolk

3. egg with permeable shell
Monotremes:
have a cloaca
no placenta
egg with permeable shell
-layed into pouch
-sticky coating
incubated in pouch for ~10 days

4. -do not have a “true placenta”
Marsupials:
-also have a cloaca
-do not have a “true placenta”
-Instead, have a choriovitelline placenta
much less intimate contact with developing fetuses
than eutherian mammals have
-Young are altricial and require a long period of
development in the marsupium (pouch) of the mother

5. -Have a “true placenta” = a chorioallantoic placenta
Eutherians:
-NO CLOACA
-Have a “true placenta” = a chorioallantoic placenta
-major evolutionary advance
-temporary organ that acts to efficiently exchange
oxygen, nutrients and waste products between the
mother and developing young
-much more intimate connection between mother & fetus
-Young are relatively precocial when born

6. Reproductive systems
Male
Testes: paired organs within which sperm develop
-hang outside of the
body within a scrotum
cooler

7. Reproductive
Systems:
MALE
formation of
copulatory
plug
contributes to
semen
Other accessory glands also may increase the volume of seminal fluid or modify or buffer the vaginal environment

8. Baculum (pl. bacula)
Sciuridae
Mustelidae

9. In all mammals except higher primates,
copulation is restricted to specific
periods of the sexual cycle called estrus
-occurs shortly before and after ovulation
Estrous cycle:
-entire sequence of reproductive events
-hormonal
-physiological
-behavioral

10. Estrous cycle Controlled largely by: FSH LH Anterior Pituitary
ESTROGEN
PROGESTERONE
Anterior Pituitary
Ovarian hormones

11. -low levels of ESTROGEN from the ovary trigger release of FSH
FSH released
-low levels of
ESTROGEN
from the ovary
trigger release
of FSH
Follicle forms
estrogen
low
Follicle begins
to form

12. LH
-as follicle forms
it releases
ESTROGEN
-stimulates LH
production
estrogen
-inhibits FSH
production
Stimulates the
thickening of the
endometrium

13. Estrous cycle When egg is mature -follicle bursts -egg released
may or may not
become fertilized

14. Estrous cycle When egg is mature -also have a surge of LH
triggers corpus luteum to
form

15. Corpus luteum
produces high levels
of progesterone
-continued thickening
of endometrium
-growth of mammary
glands

16. Progesterone
-usually provides a
negative feedback
loop that shuts down
FSH & LH
“don’t start a new
estrous cycle, I’m
pregnant!”
-All Eutherians

17. “Tyranny of the Estrous Cycle”
EUTHERIANS
MARSUPIALS
Progesterone
inhibits
FSH production
Progesterone
does not inhibit
FSH production
feedback to prevent
formation of new follicle
when female is
pregnant
no feedback to prevent
formation of new follicle
even when female is
pregnant
“Tyranny of the
Estrous Cycle”

18. “Tyranny of the Estrous Cycle”
-gestation period must be shorter than
the estrous cycle!
-severely limits the length of in utero development in
marsupials

19. Placenta
-complex of embryonic and maternal tissues
main functions:
1. Anchors fetus to uterus
2. Transports nutrients to fetus
3. Collects metabolic wastes from fetus
4. Produces hormones regulating organs of both mother
and fetus

20. Embryo can’t get very big Placentas Marsupial choriovitelline placenta
-enlarged yolk sack
-relatively little attachment
to developing fetus
Marsupial
1. gas exchange a problem
Embryo can’t
get very big
2. danger of immune response
3. Progesterone doesn’t inhibit FSH
“Tyranny of the Estrous Cycle”

21. Newborn Virginia opossum

22. Placentas choriovitelline Marsupial placenta chorioallantoic Eutherian
-enlarged yolk sac
-relatively little attachment
to developing fetus
Marsupial
YOLK
Eutherian
chorioallantoic
placenta
villi extend
deeply into uterus
very tight connection
between mother and
fetus
YOLK

23. Can have much longer gestation periods in eutherians
Placentas
EUTHERIANS
Chorioallantoic placenta
chorionic villi extend deeply
into the uterus
form a very tight connection
between mother and fetus
Trophoblast
prevents immune response
by mother to embryo
Can have much longer gestation periods in eutherians

24. Mother Virginia opossum

25. choriovitelline placenta
EUTHERIANS
MARSUPIALS
hormonal feedback loop
prevents formation of
new follicle when female
is pregnant
“Tyranny of the
Estrous Cycle”
-no hormonal
feedback loop
chorioallontoic placenta
(very efficient)
choriovitelline placenta
(not very efficient)
trophoblast
No trophoblast
(prevents immune response
by mother to embryo)
(immune response a
potential problem)
-gestation must be short
-extended lactation
-young altricial at birth
-can have long gestations
-potential for precocial young

26. marsupials tend
to have:
gestation
lactation

27. Gestation -period from fertilization to birth of young
1. Length highly variable
12.5 days (possum) to 22 months (African elephant)
2. Gestation time not necessarily correlated with size
- No true gestation in monotremes

28. Common sequence in female reproductive cycle
gametogenesis
insemination
formation of diploid zygote
attachment to endometrium
intrauteran development
birth
nursing

29. Ovulation usually spontaneous

30. Induced Ovulation
-cats, some mustelids & rodents

31. Delayed Fertilization
-insectivorous bats

32. Delayed implantation -Ursids, mustelids, phocids,
armadillos & many other groups

33. Delayed Fertilization
“norm” is spontaneous ovulation followed by events as in sequence “A”
Induced Ovulation
Delayed Fertilization
variations from
the “norm”
Delayed Implantation
Delayed Development
All of these strategies can be important for dealing
with environmental stresses, especially in highly
seasonal environments

34. Delayed Fertilization
“norm” is spontaneous ovulation followed by events as in sequence “A”
Induced Ovulation
Delayed Fertilization
variations from
the “norm”
Delayed Implantation
Delayed Development
Embryonic Diapause
only in marsupials

35. Embryonic Diapause
Embryo development halted mid-way through development!
mother may
mate again
when joey is
~6 months old
-suckling
prevents
development
of 2nd joey
Female can
have 3 young
dependent
on her at one
time

36. Lactation Functions: Production of milk by the mammary glands
Milk contains fats, proteins, lactose, vitamins, salts
Functions:
1. Provides nutrients for growth of newborn
2. Transmits passive immunity
Colostrum: first released by mammary gland following birth
-a protein-rich fluid containing antibodies that confer mother's
immunity to various diseases to young
3. May support the growth of symbiotic intestinal flora

37. Great Diversity of “Life History Strategies” in mammals
Big differences in:
-gestation period
-lactation period
-number of young
-size of young
-how developed young are at birth etc.
Many of these differences are related to constraints imposed by:
-vivipary vs. ovipary
-type of placenta
-ability to prevent immune response to embryo
-hormonal feedback
-body size and lifespan
-ecology of the species

38. Environmental Adaptations
Temps on Earth can range from -65C to +55C
Animals must have adaptations to avoid
overheating and overcooling
Regulation of body temp through behavioral adjustments
is called
ectothermy
Mammals are able to regulate their body temps using
physiological mechanisms as well
endothermy
Mammals can maintain a
relatively constant body temp
homeothermic

39. Environmental Adaptations: Reading Feldhamer Chap 9pp
Regulation of body temp through behavioral adjustments
is called
ectothermy
Mammals are able to regulate their body temps using
physiological mechanisms as well
endothermy
Mammals can maintain a
relatively constant body temp
homeothermic