Paleozoic Diversity and Mass Extinctions (midterm 2) Flashcards
Describe the characteristics of mass extinctions - what often causes them and what does it affect?
- geologically brief intervals of time > where there is more extinction than origination of new species and its a greater rate than just the background rates of extinction
- often caused by radical environmental changes on large scales
- often affect both marine and terrestrial life > tropical organisms tend to be hit hardest
- species in many different phyla are affected, but usually phyla survive
List the mass extinctions that happened during the Paleozoic (which was the biggest)
(cambrian = steady increase in species)
- Late Ordovician
- Late Devonian
- Late Permian (this was the biggest - lost 50% of the families of the time)
What were the reef builders in the Cambrian and what did they change to in the Ordovician
Cambrian : Archaeocyathids
Ordovician : Tabulate coral and Rugose coral
How were Ordovician reefs similar to Cambrian reefs and also similar to present-day reefs?
cambrian: small patch reefs but with different fauna
present-day: high diversity of organisms, dominated by suspension feeders
*also they had Tyndall stone
What are some characteristics / events to describe the Ordovocian marine community?
- major transgression (Tippecanoe) led to new habitats
> new episode of diversification
> brachiopods, bryozoans, corals
> because of lots of shallow seas with reefs - Great Ordovician Biodiversification Event
What are Ordovician Acritarchs?
- organic-walled phytoplankton
- major phytoplankton groups of Paleozoic Era
- primary food source of the suspension feeders
What are the three useful Ordovician Biostratigraphic Groups guide fossils?
(short timeframes so when we find these we can narrow it down quickly to this time period)
- articulate brachiopod
- conodonts
- graptolites
What was the scope of the End-Ordovician mass extinction?
- more than 100 families of marine invertebrates became extinct > included about 50% of North American brachiopods and bryozoans (corals)
What may have triggered the End-Ordovician Mass Extinction?
- might’ve been triggered by extensive glaciation at the south pole of Gondwana (sea level fall, cooling surface waters)
- cooler surface waters may have overstressed marine primary producers
- weathering and erosion of Taconic Highlands > absorption of C02 (Queenstone Clastic Wedge)
Explain what happened with the Silurian and Devonian Marine communities after the end-Ordovician extinctions?
and what happened to reefs
- Brachiopods, bryozoans, gastropods, bivalves, corals, crinoids, and graptolites all rebounded at the start of the Silurian
- Silurian and Devonian were period of major reef building > dominated by stromatoporoids and tabulate and colonial rugose corals
- Silurian reefs = patchy, sparse reefs
- Devonian = more robust structured reefs - similar to present day
What things/environments were mostly affected by the End-Devonian Mass Extinction
- global collapse of REEF communities
> due to continental collisions (closure of lapetus)
> black shale deposits - means anoxic conditions in the ocean
> glacial sediments suggest cooling - tropical marine groups most severely affected
- higher latitude marine communities were spared
- land-dwelling seedless vascular plants were unaffected
- Ostracoderm extinction at the end of the Devonian, coincided with the rapid evolution of jawed fish
- Placoderms greatly decreased in abundance after the Devonian
Explain the characteristics of the Carboniferous and Permian marine communities after the end-Devonian extinctions
- Brachiopods and ammonoids recovered quickly from the end-Devonian extinctions
- lacy bryozoans and crinoids reached peak diversity during the Carboniferous
- the decline of stromatoporoids and tabulate and rugose corals > led to smaller, patchier reefs of crinoids, blastoids, lacy bryozoans, brachiopods, and calcareous algae
- bony fish expanded in the late Paleozoic
What were the four main Permian Vertebrates?
Therapsids (mammal ancestors)
Parareptiles
Reptiles (archosaurs)
Amphibians
Explain the scope of the End-Permian Mass Extinction - what did it affect and what’s unique about it
called “the great dying”
- 96% of marine invertebrate species died
- 65% of land animals died > 70% of vertebrates and 33% of insects
- extended over millions of years (this is a unique aspect)
What were the potential causes of the End-Permian mass extinction?
- first idea = meteorite impact > unlikely (wouldn’t have lasted for millions of years)
- second idea = maybe related to assembly of Pangaea (unlikely bc already finished)
*mean theory = Volcanism in Siberia
- C02, F, and Cl in atmosphere
- damage to ozone layer
- climatic effects leading to: global warming, deep sea anoxia and increased seawater C02
