Lesson 11 Flashcards
MESOZOIC
3rd major time period (middle period)
- Birds first appear – no birds in the paleozoic
Mammals have already existed in the paleozoic
– but they really diversified in the mezozoic
- mezozoic was warmer this time perio d
- no polar ice caps
- much less of a lateratudinal delcimentment
—-mot as strong of a latitudinal gradient of climate as it was today
- land masses were more concentrated in pangea
^^ more or less one giant continent
IN TRIASIC
- no ocean barrier
- social behavior and other nuances of insects appear
- angiosperms appear and then radiate –> flowering platns
cretaceous
- KT boundary – point between the mesozoic and the sinozoic
by the end of the triasic
all the large animals on earth were for the most part replaced by dinosaurs
- giant dinosuars really flourished in the jurassic –> come to an end except for birds
fragmentation of pangea
- eurasia and gondwana
- occurs form the mass extension of the tethys sea – which splits the northern and southern land masses apart
- continents begin to approach the positions they are currently in the late cretaceous
first 10 million years of the triascic
were considered very barren
- early archosaurs
– eventually give rise to dinosaurs
– pterosaurcs – are not dinosaurs
late triassic
- climate shifted from moist to a hot and dry climate
- increae in mammal- like reptiles (dicynodonts)
- herbiferous vertebrates ranfed from 10g to about 1000 kilograms
—– size range suggests the habitat of an open WOODLAND
—— dense woodlnds and open savannah and grassland today do not host that range - turtles and crocodiles appear in the late triassic
- dinosaurs are the largest carniveores in the late triassic
jurrasic
earliest bird
- archiopterux
- 4 wings instead of 2
high atmospheric CO2 may have supported that huge plant life
late cretaceous
- mammals were still very small
- little rodent - mouse sized
- by the late cretaaceous – we had al the exant tetropod clades in the terrestrial faun a
- big size niche dominated by dinosaurs and a little bit of the archisairs
- major extinctions at the end of the creatceous
creataceous again (body size and food)
- complex molars emerged —– molars with multiple cusps – need to better process food
– as animals get bigger, they need a more energy-filled diet
— mammals are the only ones that undergo mastication –> the sustained chewing of food
mastication elaborated
- exposes a lot of surface area to the digestvie fluid
- more energy can be extracted
- the molars that engage in a lot of shearing (cusps of the molars)
- the cusps on the upper jaw line well with the cusps of the lower jaw so that the shearing of food is possible
big extinction – of cretaceous
-driving cause of the dinosaur extinction—-»> asteroid
at the KT boundary - there was no program to blow up the rocks before they hit like we do
- 40% of all tetropod families went extinct
- included all the avian dinosaurs
- boundary between the mesozoic and the sinozoic (KT boundary)
scientist found a large concentration of iridium in the soil
- iridium is extremely rare on earth
- but it is not rare in outerspce and on aseroids
- not rare universally
- thick concentration of iridium suggests that somehting extraterrestrial hit the earth –> suggesting that the asteroid casused a layer of particulates to circumnavigate the earth, then fall and become embedded within the earth
HIGH IRIDIUM
1st major piece of evidence that the asteroid killed the dinosaurs
2nd PIECE OF EVICENCE
- big crater discovered along the gulf of mexico and central america
- so hugeeee that you wouldn’t notice that htere was a huge crate
- only tthrouh satilite imaging that we become aware of this crater and when dated, pinpointed back to 65 million years ago aka the KT Boundary
BUT
if you look into the fossil record — you see a steady decline of dinosaurs before the asteroid hit – just a coincidence that we assign that the common agent??????
