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Mammalogy Lecture

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What are 5 ways that humans and mammals have interacted?
-Hunt/raise for food
-Hunt for sport
-Ride them for travel/sport
-Keep as pets
-Use for clothing
Artiodactyls
even-toed ungulates
examples include deer, moose, antelopes and giraffes
Lagimorphs
Rabbits & Hares
Pinnipeds
a group of marine mammals with flippers instead of feet; seals, sea lions and walruses
Cetaceans
whales, dolphins, porpoises
Elephants
Earliest known mammal domestication?
Dogs (canis lupis familaris); dates back to 30,000 yrs bp (Late Pleistocene); ancestor was likely an extinct gray wolf in Eurasia
Domestic cats?
Felis silvestra catus; dates back to 9,000 yrs bp (Early Holocene); Egypt and Middle Eastern; ancestor thought to have been African Wild Cat
Domestic cattle?
Bos Taurus; Middle East; 7,000 yrs bp; ancestor was most likely auroch (Bos primigenus)
Domestic horses?
Equus caballus; Asia; 4-6,000 yrs bp; ancestor unclear
Mammals are the only surviving...?
Synapsid Amniote Tetrapods
Mammal Phylum?
Chordata
What are the distinguishing characteristics of Chordata?
-Dorsal hollow nerve chord
-Notochord
-Postanal tail
-Pharangyeal gills
Mammal subphylum?
Vertebrata
Mammal Superclass?
Gnathostomata- Jawed Vertebrate
Mammal Class?
Mammalia
Who are the Amniote Tetrapods?
Reptiles, Mammals and Birds
Tetrapods share their most recent common ancestor with...?
Sarcopterygian Fishes; More specifically the Tetrapodomorphs
Amniote Tetrapods have...?
An Amniotic Egg with several extraembryonic membranes, including amnion, chorion, yolk sac and allantois
Amnion?
-Forms fluid filled sac around embryo
-Ectodermal, non-vascularized
Chorion?
-Ectodermal, non-vascularized
-Encloses entire embryonic system beneath shell membrane
Yolk Sac?
-Endodermal, surrounds yolk in Telolecithal Egg
-Lined with inner Mesoderm, so its vascularized
-Fuses with Chorion in Marsupials to form Choro-vitelline membrane
Allantois?
-Endodermal, outgrowth of the gut
-Lined with inner Mesoderm; vascularized
-A waste receptacle which eventually fuses with Chorion of most mammals to form the Chorio-allantoic membrane
Modern Amniotes include which lineages?
Synapsid & Diapsid lineages, where the taxonomy for the lineages is based on the number of temporal openings in the skull
How does the Mammal phylogenetic tree go?
Tetrapods- Amniotes- Synapsids- Pelycosaurs- Therapsids- Cynodaunts- Mammalia
(T.A.S.P.T.C.M)
Mammal ear bones?
-Stapes (=columella=hyomandibular)
-Incus (=quadrate)
-Malleus (=articular)
Mammal jaw joint?
Dentary-squamosal (=temporal)
What do all mammals possess?
Mammary glands
Protherians?
-Monotremes
-Is a subclass
-oviparous (producing eggs that hatch after they've been laid)
Therians?
-Marsupials & Placentals
-Theria is the subclass
-viviparous (live young that developed in a placenta)
Marsupial scientific name?
-Metatheria
-Is an Infraclass
Placentals Scientific name?
-Also called Eutherians
-Scientific name is Eutheira
-Is an Infraclass
Smallest species of mammal?
-Kitti's hog-nosed bat
-Western Thailand
-Endangered
Largest species of mammal?
-Blue whale
-Largest animal that has ever lived
-Pacific & Atlantic Oceans
Distinguishing Features of mammals?
-All endothermic and all possess hair/fur
-2 Occipital Condyles
-Bony palate
-Well developed skin glands
-7 cervical vertebrae
-4 chambered heart with a double circuit circulatory system
-Internal fertilization
When did mammals evolve?
Prior to the complete breakup of Pangaea into Laurasia & Gondwana which began 200 MYA
When did Mammals begin to diversify?
Prior to the K-T Extinction at 65.5 MYA (K-T took out all non-avian dinosaurs)
oviparous vs viviparous
oviparous means giving birth to eggs that must develop before hatching, while viviparous means giving birth to live offspring
Features of Metatherians?
Tribosphenic Cheek Teeth
Most have a marsupium to accommodate young
Largest marsupial is Red Kangaroo
Features of Placentals?
Extended gestation period
Unique Chorio-Allantoic Placenta with Villi
Double circuit circulatory system
Blue blood- right atrium- right ventricle- lungs- red blood- left atrium- left ventricle- pushes to body- cycles back to heart
Systemic circuit vs Pulmonary circuit?
Systemic circuit- the blood circuit throughout the body
Pulmonary circuit- a blood circuit to the lungs for oxygenation, follows the systemic circuit
What are the only arteries that carry deoxygenated blood?
Truncus arteries
Where does blood collect?
In the sinus vinosus, which is a sack behind the heart
Pulmonary vein?
Only vein that carries oxygenated blood
Exchange of materials between fetal blood and maternal blood takes place where?
The placenta of the mother's uterus
What is the function of the nasopharynx? Laryngeal pharynx? Epiglottis?
Nasopharynx- connects with the nasal passages from the nostrils
Laryngeal pharynx- connects the oral cavity with the esophagus
Epiglottis- folds over the glottis to close it when food is being swallowed.
Small intestine? Large intestine? Gallbladder?
Small intestine- most digestion and absorption takes place here
Large intestine- includes colon and rectum, absorbs the water and minerals from what enters it
Gallbladder- bile is stored
Inguinal canal? Vas deferens? Bulbourethral gland?
Inguinal canal- the tubular passage connecting the abdominal cavity to the scrotal sac
Vas deferens- transports mature sperm to the urethra
Bulbourethral gland- add mucosal substance to the semen that has lubricating properties
General Plan of Circulation?
-Blood from all parts of the body except lungs returns by precaval and postcava to right atrium
-Goes to right ventricle to be pumped out by pulmonary arteries to lungs to be oxygenated
-Returns through pulmonary veins to left atrium, then left ventricle, then to aorta to branches that carry blood to capillaries across body
Hepatic Portal System?
Blood is collected in the hepatic portal vein, carries to the liver capillaries where the liver stores excess nutrients as glycogen through the hepatic veins, which empty into the postcava
Pulmonary Trunk? Pulmonary veins?
Trunk- comes from right ventricle, branches into pulmonary arteries that carry blue blood to lungs
Veins- Empty red blood into left atrium
Foramen Ovale? Ductus Arteriosus? Ductus Venosus?
Foramen Ovale- opening in wall between right and left atrium, part of blood can go straight to left atrium, to left ventricle, to aorta, then back into systemic circuit
Ductus Arteriosus- Connection between aorta and pulmonary trunk
Ductus Venosus- Connects umbilical vein to postcava
Characteristics of Prototheria?
Oviparity with Telolecithal eggs
Discoidal (Meroblastic) Cleavage
Cloaca (all 3 excretory systems come here)
Complex Pectoral girdle
No defined nipples, milk is secreted on skin
How do female echidnas handle their eggs as opposed to female platypuses?
Echidnas incubate eggs and protect them within a temporary brood pouch on abdomen similar to a marsupium; Platypuses incubate in a burrow along a stream or riverbank
Monotermata eggs are highly altricial, what does that mean?
Very poorly developed at birth, so they require a high level of parental care
Tribosphenic Cheek Tooth?
Can accommodate plant & animal matter; an ancient adaptation for an omnivorous diet; seen in Prototherians and all Infraclasses of Therians (lost in most modern taxa)
Early Marsupial Dispersal?
-Dispersal across Laurasia through Land Bridges (Bering Straits)
- Leading notion is that Marsupials had colonized all of the world's ;and masses prior to breakup of Pangaea
- Few Marsupials made it to Australia, Placentals did tho
Facts about Marsupium?
-Well developed, simple folds, or absent
-Contains nipples
-Supported by epipubic bones
Fur/ Hair Development?
-Hair cells produced around a dermal papilla, which occur at the base of an invaginated epidermal follicle
-Have sebaceous glands that secrete oils around the follicles for hair lubrication
-Vascularized papillae (dermis) provide nutrients
Fur/ Hair Strucure?
-Outermost cuticular layer is a transparent layer of dead cells
-The cortex (middle) & Medulla (inner) cells contain pigment molecules
Function of Fur/ Hair?
-Thermoregulation
-Crypticity (Polar Bear)
-Species Recognition
-Group Communication (Pronghorn)
-Aposematic Functions (warning color like in skunks)
Pelage? Shedding? Vibrissae? Underfur?
Pelage- fur coat around body
Shedding- loss of fur
Underfur- similar to birds "down" feathers
Vibrissae- whiskers
Male Marsupial Reproduction?
Bifurcate penis, lacks os baculum
Scrotum anterior to penis in most
abdominal testes in marsupial moles
Female Marsupial Reproduction?
2 separate vaginas, 2 separate uteri
Medial vaginal canal that serves as birth canal
Some structural development around nipples, ranging from folds to a permanent marsupium
Fertilization in Marsupials?
Internal, occurs in proximal oviduct
Implantation occurs in the endometrical lining of uterus
Little nutrient exchange takes place via the Choriovitelline Membrane (chorioallantoic in koalas & bandicoots)
No villi so nutrient transfer is inefficient relative to Eutherians
How long is the lactation period for Marsupials?
Extended relative to Eutherians
Usually over a year
Largest of the females energetic costs during reproduction
Delayed tooth development due to this
Eutheria Characterisitics?
All viviparous
Chorio- Allantoic Placenta with villi
No epipubic bones
Date back to Cretaceous period
Oogenesis
-2N oogonia
-2N primary oocytes
-N secondary oocytes (all these in Ovary)
-N Ootids
-N Ovum (Both of these Oviduct)
Spermatogenesis
-2N Spermatogonia
-2N Primary Spermatocytes
-N Secondary Spermatocytes
-N Spermatids
-N Spermatozoa
How does sperm travel?
Epi--> Vas Deferens---> Seminal Vesicles --> ejaculatory duct
Eutherian (Placental) Reproduction: Oogenesis-Ovulation?
-A meiotic process (meiosis 1 occurs in ovarian follicles)
-Oogonia form early during foetal development
-Oogonia undergo maturation into primary oocytes
-These begin meiotic process into secondary oocytes
-To be continued in Post Ovulation
Corpus Luteum?
ruptured follicle that takes on endocrine function of secreting progesterone
Post Ovulation?
-Corpus Luteum secretes progesterone that sends a hormonal signal to uterus in prep. for implantation
-Fert. happens in proximal oviduct to stimulate meiosis 2
-Secondary oocyte divides into ootid, then matures into ovum
-2-3 polar bodies produced during oogenesis
-results in one large developed female gamete per meiotic division "conservation of cytoplasm"
Spermatogenesis details???
-Occurs in seminiferous tubules of testes
-Spermatogonia first appear, then undergo maturation into primary spermatocytes
-They then undergo meiosis 1 to produce secondary spermatocytes
-Then divide by meiosis 2 to produce spermatids
-Metamorphosize into spermatozoa
Eutherian Fertilizationn?
-Internal, with vaginal penetration by a non-bifurcated penis
-Eutherian penis with or without os baculum, females have corresponding os baubellum or not
Why Loss of Baculum? Why specifically in humans?
-Those without os baculum rely on hydrostatic pressure through blood flow into penis
-Leading hypothesis as to why lost in humans is sexual selection due to female choice
Eutherian Implantation?
-Implantation of blastocyst into the endometrium of the uterus
-Chorio-Allantoic Placenta begins to develop, has villi
-Placenta has no mixing of foetal & maternal blood, nutrients transferred by diffusion
Umbilical Cord?
-Attaches to the foetus from the placenta
-Has 2 Umbilical Artieries & 1 Vein
-Contains remnants of yolk sac and allantois
-Whartons Jelly is major component
Wharton's Jelly?
-A matrix of embryonic cells & a mucus like blend of polysaccharides
-Modified by temp. change at parturition (birth) to cut off blood flow
Development at Parturition?
-Mammals of "open" habitats tend to be more precocial
-Herbivores tend to be more precocial when controlling the environment
Mammals are highly heterogamous which means...?
Gamete size differs dramatically, female energetic investments in gamete production is high
Operational Sex Ratio (OSR)?
-Often skewed towards males
-Male:Male Competition is HIGH

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