MIdterm 1 Flashcards
Much of modern taxonomy is based on whose work?
Carl linnaeus
Taxonomic classifications from broad to narrow
Kingdom, Phylum, Class, Order, Family, Genus, Species
Which one do we want, paraphyletic, polyphyletic, monophyletic?
Monophyletic
Paraphyletic?
- includes common ancestor and some but not all of the ancestors decendants
Polyphyletic?
- does not include common ancestor of the group
Monophyletic?
- includes the common ancestor and all desendants of that ancestor
What is the major challenge with determining taxonomy?
Convergent evolution due to similar encvironments
How can we age biological material?
Radio carbon dating
- Most carbon is carbon 12, some 13 and very little 14
- present in living tissue in predicatble ratios - 98.9, 1.1, v small
- can tell how old something is by how much carbon 14 is left
- ratio of carbon 12 - 13 can infer trophic levels
How can we age geological material?
Rocks - uranium 238 - goes through predictable decay chain
What adaptation allowed early vertebrates to stay on land for the entire life cycle?
Amniotes/ amniotic eggs - dont have to return to water to breed
4 key innovations to remain on land throughout the life cycle?
- dessicant resistant skin - dont dry out
- thoracic leading to diaphragmatic breathing - creating negative pressure to suck air in
- water conserving kidneys - concentrating waste prior to eliminating - minimal water use
- internal fertilization
three types of amniote skulls - which one are we?
Anapsid - turtles - no skull hole
Synapsid - mammals - one skull holes - we are this one
Diapsid - two skull holes
- holes are for muscle and weight reduction
How many bones make up the mammal lower jaw?
only one
What is the secondary pallete?
Developed secondary pallete allows for breathing through nose while mouth is occupied - crocodiles and dinosaurs cant do this
Which jaw joint makes a mammal a mammal
denturay squamosal jaw joint being the jaw joint - formed hammer and anvil in ears in later mammals
- single dentary bone that connects directly to the cranium
In the transition to the dentary squamosal jaw joint, where do the articular and quadrate bones end up?
End up making the malleus and incus in the ear bones
- enables mammals to have some of the best hearing
What happened to the overall size of mammals in the late Triassic and early Jurassic?
Mammals got very small for a time - large mammal like reptiles got outcompeted by the dinosaurs
The three semicircular canals in the inner ear are responsible for what?
Balance - allow to determine when upsidown
What is precise occulsion?
Teeth that fit together perfectly
What are tribosphenic teeth?
Three pronged type molar with grinding and cutting edges
Two families / species in order monotremata
Ornithorhynchidae - platypus
Tachyglossidae - Echidna - 4 species
3 key characteristics of monotremes?
- egg laying
- lack of nipples
- presence of a cloaca
Purpose of the epipubic bones in marsupials?
something to do with pouch, found in metatherians and everything thats not a eutherian
What is the diprotodont condition?
Two lower incisors
Why might there be ecological constraints on marsupial diversity?
Due to method of reproduction + really short gestation period - marsupials need thick shoulder girdle to crawl to the teat which restricts the level of diversity compared to placental mammals
Between animals of the same size, how are gestation and lactation periods different between marsupials and placental mammals
gestation is much shorter in marsupials but lactation is much longer
- overall period from birth to weaning is much longer in marsupials
Why were mammals and birds set up to take over once the KT extinction occured?
Already small, could regulate temperature, and were insectivorous - which were the main food source left after the extinction
What happens with insectivorous animals teeth?
Generally lose teeth
What was condylartha?
Extinct group of carnivorus ungulates that evolved into todays ones
Three groups that moved towards carnaceal teeth?
carnivora
creodonta
mesonychidae
What is carnivore dentition
upper fourth premolar and lower first molar are main carnacial pair in tru carnivores
Are cats obligate carnivores?
pretty much, can survive with only meat and bones easily
- pretty much obligate carnivores
- cannot tastse sweet - if you dont use it you lose it
How was smilodon taking down prey?
Had long saber teeth but weak bite force , would slam head into prey instead
List the periods in order from the start of mammals to today PEOMPP
First mammals were in the Triassic
Triassic, Jurassic, Cretaceous, Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, Holocene (Today)
What is the first branch off of amniota that gave rise to the mammals
Synapsids / synapsida - had an infratemporal fenestra
Happened in the permian
Key adaptations of Synapsids?
Dessicant resistant skin - early carboniferous was warm and wet, but the Permian was much cooler and dryer, needed to be adapted to those conditions.
- amniotic egg from the amniota was incredibly important for terrestrial vertebrates since they could complete entire life cycle on land without being restricted to water
- thoracic breathing, negative pressure sucked air in
- water conserving kidneys - also important in dryer environment / to be less reliant on water
- internal fertilization - allowed for greater survivability of young, young could be better guarded
What skull adaptation distinguishes synapsids from anapsids and diapsids?
Synapsids had one temporal fenestra (hole formed by the postorbital, squamosal, jugal and quadrate bones)
Anapsids had none
Diapsids had two
- made the skull lighter without sacrificing strength.
- saved energy by using less bone.
- probably provided attachment points for jaw muscle
What came after the synapsids?
Therapsids - expansion of jaw muscles, erect gait, bigger cerebellum
Mid-Permian
What came after the therapsids?
Cynodonts - enlarged dentary bone, reduced post dentary bones, postcanine teeth (teeth differentiation)
Early Triassic
What came after the cynodonts?
Early mammals / mammal like reptiles in the late triassic
What happened to leg position in early mammals?
Legs began to move under the body in the cynodonts / early mammals
What was important about the development of the secondary palate in the late cynodonts?
enabled breathing while eating and lead to highly developed senses of smell
What defines a mammal?
Having a single bone for the jaw that attaches to the cranium, only the dentary bone and squamosal
Quadrate bone became incus and articular bone became malleus
What happened in early mammals? why might this explain the mammal jaw joint we see today
They all got small and hunted at night, reduction in size can come with a reduction in bones
What is an example mammal of the transitional stage between mammal-like reptiles and mammaliaformes (almost the full mammalian jaw joint)
Morganucodon - Late triassic - had teeth differentiation
What is an example of a proto mammal having the proper jaw joint?
hadrocodium - early jurassic
What was sinoconodon?
Early proto mammal seemingly related to morganucodon but it replaced teeth throughout its lifetime - early jurassic
What was juramaia?
early mammalia, small rat from late jurassic
What was eomaia?
early mammalia - possible ancestor to all mammals, early cretaceous
What were multituberculates?
Early rodents but not actually rodents - had continuously growing incisors like rodents but different clade - died in the late eocence (tertiary)
Why are monotremes so important to mammalogy?
middleground between mammal and reptile, genome still has reptillian characteristics - especially with venom very similar toxins / proteins to reptile venom
How is the female reproductive anatomy different between eutherians and proto / metatherians?
eutherians have one uterus from two fallopian tubes where the other two have two uteri directly connected to the fallopian tubes
What bone is unique to proto/metatherians?
epipubic bones - better structure / support for very tiny babies
- strong shoulder girdle as well for crawling to teat / milk glands in skin
What jaw bone is unique to marsupials?
marsupial shelf
Why were marsupials / prototherians born so early?
Had to fight the immune system of the new fetus in the mother, wanted to get rid of the foreign body as soon as possible, hence early birth
What was thylacosmilus?
Early marsupial saber tooth tiger - example of convergent evolution - had strong shoulders and lower jaw plate to prevent teeth breakage - miocene - existed at same time as barbourofelis - early sdaber tooth cat
What was the yolk sac placenta?
Reproductive structure in metatherians, very large yolkl sac to meet nutritional needs of embryo, little to no chorionic villi penetrating egg (as in placentals) so no nutrients from that
no chorioallantoic placenta. complete reliance on yolk sac placenta (choriovitillenic placenta instead)
Which metatherian may be a middle stage of the evolution of the mammalian chorioallantoic placenta?
the bandicoots
Why is longer gestation important?
can develop more complex structures, metatherians must maintain certain characteristics like thick shoulder girdle and epipubic bones to move to pouch immideately after birth
What is embryonic diapause?
the ability to be nnursing multiple life stages at the same time in metatherians like kangaroos
Difference between gestation and lactation periods in marsupials and placentals?
Marupials have very short gestation but much longer lactation
Placentals have long gestation and short lactation, overall shorter than marsupials
What was the KT extinction event?
Inbetween the cretaceous and paelogene - AKA K-PG extinction event
Massive asteroid hit gulf of mexico
- massive crater that ejected dust clouds killing basically everything and all dinosaurs, super hot temperatures followed by an impact winter
4 major origins of modern eutherians?
xenarthra in SA and afrotheria in africa, laurasiatheria in NA / asia and euarchontoglires in europe
Evolutionary significance of terrestrial insectivory?
mammals were all small, everything was small after KT, insects provided good protein source, easy for small mammals to get
What was cimolestes
small early mammalian insectivore
cretaceous
What is solenodon?
mammal with venom, evolved very early on
pleistocene
Anatomical and physiological adaptations that enable insectivory
- specialized teeth or lack or teeth for myrmecophagy
- venom in solenodons, moles, short tailed shrew
- long tongues
- loss of zygomatic arch to keep face narrow
Examples of convergent evolution in insectivorous mammals
aardvarks and anteaters, both with long faces, fewer / no teeth, digging claws and long tongues
loss of zygomatic arch for long face in tenrecs and anteaters
Compare and contrast solenodons, tenrecs, armadillos, pangolins
Key mammalian lineages that are insectivorous
Aardvarks, anteaters, solenodons, hedgehogs, moles, armadillos, tenrecs
What are examples of Xenarthra
armadillo, sloth, tamandua, anteater
When /what was dimetrodon?
sailback synapsid from the Permian
When what was andrewsarchus?
precursor to whales, eocene, member of carnivorus hoofed mammals, likely mostly aquatic
- early example of terrestrial carnivory
Where might terrestrial carnivory have first evolved?
in the metatherians? Thylacine, thylacosmilus, thylacoleo
What of the four major mammalian groups contains carnivora?
laurasitheria
What is an early group of carnivores and what were they?
Condylartha, part of the laurasitheria, were a group of carnivorus ungulates
- Chriacus - paelocene
- Arctocyon - eocene
What era did carnivora first appear?
Paleocene
How does cimolestes fit in with terrestrial carnivory?
was likely an insectivore but also a precursor to carnivora, had differentiated teeth and long canines, with the tribosphenic molar
What were creodonts?
an order of extinct carnivorus mammals, had similar teeth with the carnassial shear compared to carnivora, similar but they were not the ancestors
- Oxyaenidae - middle eocene
-Hyaenodontidae - hyaenodon - late eocene to miocene
What was the main difference in teeth between creodonts and carnivores?
Creodonta teeth - large carnassial molars got bigger from m1 to m3 towards the back of the mouth - multiple carnassial teeth
Carnivora teeth - m1 generally bigger and sharper, main shearing tooth - only one carnassial tooth
Why dont cats like sweets?
molecular analysis shows that big cats have a faulty taste receptor gene, might account for why they are such effective carnivores
What was homotherium?
lesser known saber toothed cat of the ice age, diverged from smilodon
What was pachycrocuta?
genus of prehistoric hyenas the size of lions, from early pleistocene
Dinofelis and pachycrocuta did osteophagy in what group?
ate human bones
