Lecture 34 & 35 Amniotes - Mammals Flashcards
where did animals evolve from?
- synapsids
what does the synapsid clade include?
- reptile-like sailbacks
- numerous therapsida – mammals and close relatives
all non-mammalian syapsids are?
extinct
all that is left is the mammals in therapsida
what are mammals characterized by?
- enlargement of dentary bone in the jaw of therapsida ( in mammals jaw only consists of this bone)
- development of a secondary palate (bone partition between nasal and oral cavities – simultaneous chewing and breathing
what are derived characteristics of mammals?
- mammary glands
- hair
- endothermic
- movement of leftover jawbones to middle ear
- dentary-squamosal jaw joints
- different detention
- occluding of teeth
- two sets of teeth over lifespan
- larger brains than vertebrates
- vertical placement of limbs beneath the body
- diaphragm
- all mammals transfer sperm via intromission
what do mammary glands do?
- secrete milk for offspring
what is hair made of?
fine cylindrical keratin fibres
- might have whiskers
in regards to avian endothermy, how did mammal endothermy arise?
independently
- high metabolic rate
- hair and fat help for thermoregulation
how many ear bones do mammals have?
3, reptiles have 1
- allow for higher pitched sound
- eardrum moves to deeper in mammals
what does dentary squamosal mean?
dentary: lower jaw bone - carries teeth
squamosal: small cranial bone
both meet to form a joint
- in most gnathostomes joint consists of articular and quadrate
how is mammalian detention different from reptile?
- greater diversity of tooth form
what does a closer occlude lead to?
greater grinding of food
- bigger surface area
what are the two sets of teeth of mammals?
- milk and adult (reptiles replace) teeth constantly
what develops in the brain
neocortex – sensory percept, language, motor commants - HIGHER FXNS
how does vertical placement of limbs help mammals?
greater support of the body, greater efficiency of movement
what are the three extant lineages of mammals?
what are they based on?
monotremes - single order
marsupials -single order
eutherians - multiple order
based on modes of birth and development
what are monotremes?
mammals - consist of echidnas and platypus
- lay eggs that are oviparous, but provide milk for young after they are born
- no nipples - specialized hairs
- cloacas
- lack teeth as adults
- feed on invertebrates
what are characteristics of both marsupials and eutherans?
- viviparous - birth to live young
- placenta provides nourishment to young initially – extraembryonic membranes and lining of the uterus, transfers nuttients and oxygen from mother’s blood to embryo’s blood
- post birth: nurse on milk from nipples
what are marsupials?
- opossums, kangaroos, koalas
- embryo develops within
what are characteristics of both marsupials and eutherans?
- viviparous - birth to live young
- placenta provides nourishment to young initially – extraembryonic membranes and lining of the uterus, transfers nuttients and oxygen from mother’s blood to embryo’s blood
- post birth: nurse on milk from nipples
what are marsupials?
- opossums, kangaroos, koalas
- yolk-sac placenta, live born
- embryo develops within a placenta in the mother’s uterus: young very briefly nourished via placenta
- born as partially developed embryos
- convergent evolution with mammals, analogous structures
- started in NA found their way to SA then Australia via Antartica
what are eutharians?
non marsupial mammals
- more complex placenta – chorioallantoic placenta
- complete embryonic development in uterus, nourish young via placenta until very well developed
NO CLOACA
whats up with cloacas?
Monotremes and marsupials have a single cloaca (though marsupials also have a separate genital tract), while most placental mammal females have separate openings for reproduction, urination, and defecation: the vagina, the urethra, and the anus
what are bats?
eutherians
- only mammals capable of flight
why did mammals return to water?
- abundant aquatic food sources
- escape from terrestrial predators
- few aquatic competitors
- availability of warm, shallow waters
what are pinnepeds?
seals- semiaquatic
- descended from monophyletic carnivora lineage that includes otters, bears walruses
what is the evolution of cetaceans?
- whales & dolphins (cetaceans), manatees, dugongs initially grouped together because of superficially anatomical structures – ANALOGOUS
- cetaceans descended from even toed ungulates (hoofed mammals)
- hippos are the closest living relatives of whales, but they are not the ancestors of whales
what are adaptive changes of mammals who return to sea?
- shortening of legs
- hands and feet enlarge – paddles
- tail longer and more muscular
- nostrils – blowholes
what are adaptive changes of mammals who return to sea?
- shortening of legs
- hands and feet enlarge – paddles
- tail longer and more muscular
- nostrils – blowholes
- hands, limbs and pelvis evolve to be reduced in size and separate from backbone – vestigal hind limb
- reduced neck fxn - fusion of cervical vertebrae
- other adaptations for feeding in water
- increased use of whole vertebral column including back and tail for locomotion
- swim: move tails up and down instead of back and forth like fishes, reflects ancient terrestrial heritage
what is order dermoptera? colugos?
arboreal gliding mammals ex: sugar glider
- sister group to primates
what is order primates?
lemurs, tarsiers, monkeys, apes
- generalist mammals
- arboreal
- hands and feet adapted for grasping
- thumb and toe widely separated from other digits
- fully opposable thumb, pentadactyl appendages
- flat nails
- large brain, short djaws
- forward facing eyes, stereoscopic vision, depth perception
- complex social behaviour
- shortened snouts
