Chapter 12 Flashcards
What are extant species
- species that are still present today
- species whose members died off are called extinct species
What are the five major mass extinctions that paleontologists recognize
- End of Ordovician
- Late Devonian
- End Permian
- End Triassic
- End of Cretaceous
Which animals went extinct in the end of Ordovician
- mainly marine invertebrates
- >at that time, terrestrial organisms only had begun to evolve
Which animals went extinct in the late Devonian
-marine invertebrates and some early vertebrate clades
Which animals went extinct in the End Permian
-marine invertebrates, insects, synapsids and anapsids
Which animals went extinct in the end of Triassic
-marine organisms and pseudosachians
Which animals went extinct in the end of the cretaceous
-marine invertebrates, marine reptiles, pterosaurs, dinosaurs and birds
- land plants also lost many species and insect diversity fells
- killed all non-avian dinosaurs
- marine diapsids called mosasaurs and plesiosaurs died out
- so did many varieties of corals, plankton and ammonites(squids and octopi)
Did mammals, turtles, corcodiles, amphibians and fish make it through the End-Cretaceous Extinction
- yes
- > although many of the larger species in these groups did not
- it seems like large animals and photosynthetic organisms were the most likely to die off
- > small animals and those that are semiaquatic had the best chance of surviving
Are all animals that survived the end cretaceous extinction around today?
- no
- > eg; champsosaurs are a good example
- > they were crocodile like aquatic diapsids
Name some recent extinctions
- Tasmanian tiger
- passenger pigeon
- the Carolina parakeet
-extinction of these species was the result of intense hunting and habitat loss
Are scientists predicting a sixth mass extinction event currently
- yes
- > the new mass extinction is being brought about by sudden global climactic change and large-scale ecosystem destruction and degradation
What is iridum
- it is a rare element on earth
- >a common component of meteorites
What are tektites and shocked quartz
Tektites
->tiny pieces of rock that have been melted and cooled
Shocked Quartz
- > form of mineral quats with a unique internal structure
- > can only be created by a power exposure ot a shockwave
- > like those created by a meteorite impact
Have scientists found a thin layer of grey clay between the Cretaceous and Paleogene boundary?
- yes
- > it is made up of iridum, tektites and shocked quartz
- all three being present all over the globe would have required an enormous shower of large meteorites or a single tremendous meteroirite impact
What are cenotes
-they are limestone sinkholes
What did geologists in Mexico’s Yucatan Peninsula find
- there were cenotes arranged in crescent shapes many miles long
- each end of the crescent seemed to terminate at the end of the peninsula
- > however, it was foundd that the cenotes did not actually terminate at the end of the peninsula but were pushed up
- > it actually continued along the ocean floor and was a huge continuous ring over 180 km in diameter
- note based on the crater’s size, it has been calculated that the meteorite made must have been 10 kilometres in diameter
- > larger than Mount Everest
Could the ice age have been responsible for the end Cretaceous extinction
- the Cretaceous period was followed by an ice age
- > while average global temperatures did fall after the Cretaceous, this temperature fall was gradual
- > and it was million of years before a true ice age resulted
What is the current prevailing theory for the cause of the End-Cretaceous extinction
- the cause is more cosmic
- > without a doubt, very large meteorite struck the Earth in the Yucatan peninsula at about the same time we see a mass extinction in the fossil record
- the initial impact caused huge tsunamis and sent a great cloud of super-heated rock and dust high into the atmosphere
- > the rocks and large pieces of debris quickly fell to the Earth and started wildfires
- > smaller pieces of debris next began to fall and as they did, they were heated by air friction
- > this hot dust raised global temperatures for hours after impact and cooked alive animals that were too large to seek shelter
How did the residual haze after meteor impact photosynthetic plants
- the residual haze would have reduced sunlight
- > killing many photosynthetic organisms
- > some scientists predicts that photosynthesis may have stopped for a decade
- the reduced sunlight may also have brought on a sudden drop in global temperatures
- > large active animals with high energy needs were highly susceptible to these catastrophes
- note smaller omnivorous terrestrial animals like mammals, lizards, turtles or birds may have been able to survive as scavengers
- > feeding on the carcasses of dead dinosaurs, fungi, rotts and decaying plant matter
-smaller animals with lower metabolism were best able to wait the disaster out
Is there a chance that a complete or a nearly complete DNA strand of a dinosaur could be preserved
- not very likely
- > as DNA is a delicate substance and quickly breaks down over time
-even if DNA was found intact, cloning is a difficult process
Can current birds DNA be used to created dinosaurs
- it has been proposed that a dinosaur could be resurrected by hatching a bird with its advanced DNA sequences turned off and its ancient ancestral sequences turned back on
- > for the moment, performing such genetic manipulations as well is beyond our understanding and technology
