Introduction to Mammals + Subclasses Flashcards
Maintaining body temperature independent of the surrounding environment
Endothermic
Glands unique to mammals
Sweat, mammary
Flat, shovel-like teeth used for grasping, nipping, gnawing
Incisors
Long teeth used for holding prey, fighting and biting
Canines
Flat or cusped teeth with 2+ roots and 2 cusps in humans, used in breaking, grinding, crushing, shearing
Premolars
Flat or cusped teeth with 2+ roots, used in breaking, grinding, crushing, shearing
Molars
The last upper premolar and first lower molar, bladelike for shearing
Carnassials
Gap in dentition where canines lack
Diastema
The three groups/lineages/subclasses of mammal
Prototheria, Metatheria, Eutheria
Prototheria meaning
earliest beasts
Only remaining order of prototheria
Monotremata (monotremes)
Monotreme meaning
one opening, in reference to cloaca
Unique features of monotremes
Lay eggs (oviparous), sweat out milk
Monotremata
4 echidnas and the platypus
Metatheria meaning
primitive beasts
Metatheria
Marsupials (8 orders)
Shared trait of metatheria and eutheria
Live birth
Female reproductive traits of metatheria
Bifurcate reproductive tract with 2 vaginal canals and 2 uteri (didelphis)
Metatheria placenta
Poorly developed
Male reproductive traits of metatheria
Bifurcate penis, scrotum anterior to penis, no baculum, used for sperm delivery only
Shared trait of prototheria and metatheria
Cloaca (metatheria is modified)
Unique reproductive trait in 50% of metatheria/marsupials
Marsupium (pouch)
Eutheria
Placental mammals, global
Why are marsupial young born so early?
Investment is in nursing, not pre-birth development. Uterine gestation and placenta are weak but the marsupium does the rest of the work
Eutheria meaning
good beasts
Female reproductive traits of eutheria
Singular tract and uterus, fertilization is always internal
Why do eutheria young gestate so long?
Development occurs primarily in gestation in exchange for relatively short period of nursing, young are born relatively developed
Placenta
Mass of vascularized tissue that nourishes fetus while in the uterus, exchange occurs across umbilical cord
Male reproductive traits of eutheria
Singular penis, scrotum posterior to penis, some have baculum
Male reproductive parts in all eutheria
Paired testes, accessory glands, duct system, copulatory organ
