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38 Cards in this Set
- Front
- Back
Monotreme reproduction
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-ancestral amniotic pattern, +period of lactation
-egg 3mm at ovulation -coated in albumin -shell gland lays down shell that calcifies -2-3 weeks in uterus before laying -15 mm when laid -embyonic development and growth fueled by yolk |
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3 layers in placenta of therians
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-maternal layer - endometrium (highly vascularized)
-outer embyonic later = chorion -inner embryonic layer = vitellin and allamtois |
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general metatherian reproduction
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-retain shell gland - shell membrane deposited around fertilized egg
-placenta is choriovitelline |
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parts of the placenta, from outer to inner
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-chorion
-extraembryonic coelom -vitellin or allamtois -amnion -embryo |
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metatherian placenta
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-attaches loosely to endometrium
-shallow depression at point of attachment -allamtois recedes, vitelline expands to fill coelomo -maternal nutrients taken up indrectly -"uterine milk" bathes embryo, nutrients diffuse into yolk sac |
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eutherian placenta
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-vitelline recedes
-allamtois expands to fill coelom -implants deeply into endometrium --penetration by highly vascularized chorionic villi --endometrium erodes at point of implantation --increases surface area for absorption of nutrients from maternal to fetal circulation |
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6 layers separating maternal from fetal blood
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-maternal capillary endothelial cells
-connective tissue -epithelium of endomettrium -chorion -connective tissue -endothelial cells of embyronic capillary |
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epitheliochorial
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-6 tissue layers separating maternal from fetal blood
-small degree of erosion of endometrium -Cetaceans, Suids, Equids |
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Endotheliochorial
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-maternal capillaries in direct contact with chorion
-4 tissue layers separating maternal from fetal blood -Carnivora |
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hemochorial type
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-maternal capillary walls erode, chorionic villi bathed in maternal blood
-Chiroptera, Insectivora, Primates |
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Hemoendothelial
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-all maternal tissues erode, chorion and embryonic tissue erode
-single layer separating maternal from fetal blood -some insectivorans, Rodentia |
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Which type of placenta is most efficient in nutrient transfer between maternal and fetal blood?
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-Hemoendothelial
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afterbirth
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-maternal portion of placenta shed
--large amount of bleeding - deciduous --little afterbirth - nondeciduous |
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Peramelidae (reproduction)
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-has chorioallamtoic placenta
-almost no endometrial erosion |
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iteroparous
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-more than one reproduction cycle per lifetime-most mammals
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Antechinus
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-semilparous
-one cycle per lifetime |
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estrous cycle contains two cycles, what are they?
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-ovarian
-uterine |
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differences between reproduction cycle of eutherians vs. metatherians
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-eutherians - pregnancy interrupts estrous cycle, post-partum estrus after birth
-metatherians - gestation occurs within an estrous cycle |
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control of cyclicity
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-pituitary hormones
-regular or induced |
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three types of induced cyclicity
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-visual cues
-behavioral cues -environmental cues |
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visual cues for cyclicity
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-testicles quiescent (housed in abdomen), body temp too high for spermatogenesis
-descend into scrotum via inguinal canal -sight of scrotal testicles incudes estrous cycle |
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behavioral cues
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-suckling
-copulation (felids) |
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environmental cues
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-seasonality of reproductive cycles
-Microtus montanus - G-MBOA --ensures young are born when food is available -Dipodomys - low seed set -> 0% individuals may become reproductively active |
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four ways to optimize time of birth within an estrous cycle
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-delayed fertilization
-delayed development -delayed implantation -embryonic diapause |
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delayed fertilization
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-Vespertilionids, e.g. Myotis
-spermatogenesis ends in late August -sperm stored in epididymis until breeding season -breeding occurs at hybernacula in late October -females store sperm in uterus -fertilization in late February, give birth late to mid spring when insect populations are highest |
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delayed development
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-few Phyllostomids, e.g. Artibeus
-fertilizaiton occurs normally -blastocyst implants into endometrium mid-summer, development ceases until early winter -birth at end of dry season when fruit is plentiful |
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delayed implantation
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-some bats, carnivorans, xenarthrans, artiodactylans
-fertilization occurs normally, development continues to blastocyst stage -development halts prior to implantation -blastocyst floats in oviduct or uterus encased in zona pellucida up to 9 months -when zona pellucida deteriorates, implantation occurs |
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examples of delayed implantation
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-ursus americanus (obligate)
-many rodents (facultative) |
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evolution of delayed implantation
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-evolved once, has been lost multiple times independently, esp. Mustelidae
-seasonality - temperate climates = evolution of DI -longevity - shorter-lived = loss of DI |
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embryonic diapause
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-like delayed implantation, except that metatherians don't implant
-facultative - only occurs if older joey is suckling -post-partum estus - second fertilization after birth of first -suckling triggers endocrine system to hormonally suppress development of second embryo -can last up to 235 days -ceases if older joey dies or starts leaving pouch -two adjacent nipples providing different nutrient content |
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relationship between body size and number of offspring
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-larger body size = fewer offspring
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small body size
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-high BMR and short lives
-large litters -short gestation -altricial young -rapid post-partum growth rate -reach reproductive maturity at young ages -short generation times -R-selected traits |
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R-selected traits
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-optimize contribution to future generations by creating large number of low quality offspring
-high population growth rates |
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large body size
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-low BMR and long lives
-long gestation times -long estrous cycles -low litter sizes -young tend to be precocial -long periods of lactation, slow post-partum growth rates -K-selected traits |
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K-selected traits
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-genetic contribution to future generations is optimized by creating a low number of high quality offspring
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exceptions to the body size reproduction thingy
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-Microchiroptera (small, low BMR, heterothermic, one or two offspring annually, late age at first reproduction)
-Macroscelids (1-2 young after long gestation, precocial young) -Histricognathous rodents (e.g. Ctenomys - longer gestation period) |
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Mirounga
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-pinnipeds execption to rule - rapid post-partum growth rates
-Mirounga young double body weight in 10 days` |
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altricial vs. precocial young
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-risk of mortality high - altricial
-risk of mortality low - precocial -seasonality not predictable - altricial (loss of litter has less impact on energy budget) -seasonality predictable - precocial -predator avoidance passive - altricial -predator avoidance active - precocial |