Transcript Questions in Mammalian Reproduction I

Mammalian Reproduction I
Reproductive Strategies
Reproductive Anatomy & Physiology
Vaughan: 334-344, 354-359, 450-455
EEOB 625
4 February 2004
Mammalian Reproduction
Evolutionary Considerations
• Why study reproduction? Evolution, Ecology,
Physiology, and Animal and Human Health
• Life history strategies: a suite of adaptations providing a
solution to major problems of existence (3 major ones)
• Body size, nutritional strategies, and length of gestation
- Exceptions to the positive correlation of gestation
length with adult body size related to diet
Mammalian Reproduction
Evolutionary Considerations (cont.)
• Basic Modes of Reproduction & number of eggs:
Oviparity, Ovoviviparity (egg retention) & Viviparity
• The" mammalian solution”: Polyestry and relatively
short generation intervals related to high metabolic rates
• Trade-offs on litter size and the number of litters per
lifetime
• Seasonal breeding: Proximal cues and the ultimate
selective factor
Questions in Mammalian
Reproduction I
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Why study reproduction?
What is the advantage of sexual reproduction?
Why is monogamy rare & polygyny common in
mammals ?
Why do most female gray squirrels come into
estrus in early February and July?
Female reproductive tracts: Are opossums and
humans as different as they can be?
Why the scrotum in male mammals?
Fig 9.1, Feldhamer
Fig 9.1c, Feldhamer
Sperm pairing in
the epididymis
of didelphid
marsupials
Fig. 2, Harder & Jackson (1999)
Testis &
Scrotum of
a ram and
a bore
Fig. 9.4, Feldhamer
Questions in Mammalian
Reproduction II
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Estrous cycle and menstrual cycle:
Is the difference in the name?
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Are the physiological, morphological, or
behavioral changes different in the two types?
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Induced vs. Spontaneous ovulation: What is
same and what is different about LH?
Estrous Cycle, Estrus & Ovulation
A. Estrous cycle: a sequence of physiological,
morphological, and behavioral changes
punctuated by recurring periods of estrus and
ovulation
B. Follicular and Luteal Phases punctuated by estrus
and ovulation
C. Control of estrus and ovulation: Estrogen, LH,
and Progesterone
D. Induced estrus and induced ovulation:
Turner &
Bagnara, 1976
Fig.9.6, Feldhamer