Cenozoic Life (final exam) Flashcards
The Cenozoic is also known as what?
The Age of Mammals
Summarize the broad changes in plant and animal life in the Cenozoic
- following the major extinctions at the end of the Cretaceous > mammals rapidly diversified to life on land, in the seas, and in the air
- marine invertebrates diversified
- flowering plants became the dominant kind of land plants on Earth
- first appearance of grasses
What kinds of marine invertebrates were thriving and not thriving during the Cenozoic
- ammonites and rudist bivalves were extinct
- Coral were the dominant reef builders again
> Gastropods and bivalves (molluscs) were diverse
> corals, bryozoans, and echinoids most common
Explain the ocean water temperature during the Cenozoic
There was greater ocean water temperature variation
- changing ocean current and latitudinal temperature gradients > more provincial marine fauna
Explain how Phytoplankton were evolving in the Cenozoic and which were dominant
Only a few species in each major group of phytoplankton survived into the Paleogene
- Diversified and expanded during the Cenozoic
Benthic foraminifers, radiolarians common
Diatoms flourish - increase in dissolved silica in ocean water
Explain Cenozoic Vegetation and what largely controlled the vegetation
- Angiosperms continued to diversify and become more abundant
- climate largely controls the distribution of plants
Explain the relationship of climate to the abundance of smooth/incised plant leaves (and through the Cenozoic)
Smooth edged leaves = warmer climate
Incised leaves = cooler climate (perhaps glaciation)
Through the Cenozoic: decrease in temperature and therefore decrease in smooth leaved plants
What are some examples of modern orders of birds that appeared in the Cenozoic?
owls, hawks, ducks, penguins, and vultures
Explain the difference between flightless vs. flight birds
Which were dominant and what were the rest?
Flightless and flight birds differ based on the variations in structure that are required for flight
- flightless birds show more variation (ex. ostrich and penguin)
- flight birds look more similar to each other (less variation)
Large flightless birds were the dominant predators > most others were wading birds that lived along the shore
Explain the great mammal diversification in the Cenozoic - what three groups classify them?
- mammals lived with dinos for over 160 million years
- during the Mesozoic, mammals were not very diverse and were much smaller
- mammals quickly diversified after the Cretaceous extinction > filled ecological niches left vacant by dinos and sea reptiles
3 groups for all mammals: monotremes (eggs), marsupials (pouch), and placentals
Explain the Paleocene mammals (very first Epoch in the Cenozoic)
What survived the extinction and what new mammals came up?
Survivors from K-Pg extinction event > marsupials, insectivores, and rodent-like multituburculates > mostly small animals and lived on land/could burrow (compared to those living in trees who would’ve died)
New Paleocene mammals > rodents, rabbits, primates, carnivores (only slightly different from herbivores at this time), and ancestors of hoofed mammals
Explain the Eocene climate and what new groups of mammals appeared?
Climate was subtropical, and the lush forests were inhabited by new groups > ancestors of horses (had multiple toes), camels, elephants, whales, rhinos, and bats
List the new groups of mammals that we see in the Oligocene and Miocene
One-toed horses, small camels, turtles, rhinos, cranes, giraffe-like camels, three-toed horses
What is all included in the Cenozoic Rodent group? What is the vastness of rodents?
Insectivores, rodents, rabbits, and bats
(insectivores since Mesozoic)
Rodents make up 40% of the mammal species
List some of the Cenozoic carnivore groups and what is special/different about carnivores
Bears, seals, weasels, skunks, dogs, cats (carnivores diversifying during this time)
- They could have a varied diet (omnivores eat plants as well)
- Have specialized teeth for shearing
- Different hunting styles
- fossils not as common because the grassland environments where they lived are not favourable for fossilization
What are ungulates? (examples and 2 groups)
They are hoofed mammals
- deer, camels, horses, pigs, whales, rhinos
Even and odd toed groups:
Perissodactyls (1 or 3 toes)
Artiodactyls (2 or 4 toes) > camels and bovidae (cows, bison, sheep, antelope)
What group do camels belong to? Explain their evolution and migration
Camels are Artiodactyls (even-hoofed)
Originally found in North America
- earliest were 4-toed, later all 2-toed
- they were Giraffe-like in Oligocene and Miocene
- migrated to south america and asia in Pliocene
- went extinct in North America in Pleistocene
Describe the significance and evolution of whales in the Cenozoic
- whales are Artiodactyls?
- blue whales largest animal ever
- Eocene ancestors were dog-sized and were terrestrial > evolutionary pattern shows a return to water
- Oligocene whale Aetiocetus had both baleen (strain system in the mouth) and teeth
Horse fossils are common in North America - what do they show regarding teeth evolution?
This evolutionary trend is fairly well known > teeth get tall to account for switch from browsing (leaves) to grazing (grasses)
What are perissodactyls
(common ancestor when?)
(greatest diversity when?)
examples?
They are odd hoofed mammals
- common ancestor in Paleocene
- greatest diversity in Oligocene
Ex. rhinos, tapirs, horses
What is the Proboscidea group?
Includes elephants and elephant-like friends
- can be very large
- long snouts (trunk)
- many have tusks > enlarged incisor teeth
- mammoths and mastodons
Describe the Mammoths and Mastodons (when did they evolve and become extinct and what makes them different)
Both are a part of the Proboscidea group
Mammoths:
*browsers
- evolved in Pliocene and Pleistocene
- lived in Africa and on all northern continents until end of Pleistocene
Mastodons:
*grazers
- became extinct only a few thousands years ago
- evolved in Africa
- one genus reached South America
What is the significance of Intercontinental Migration (how did it happen)? What does it account for?
Accounts for similarities of animals on different continents
Low sea level periods during glaciation exposed land bridges connecting some continents
- tectonic uplift connected NA and SA (*Great American Biotic Interchange > 50% of SA mammals originated in NA, 20% NA mammals originated in SA)
- Africa became close to Eurasia
What was the scope of the Pleistocene Extinctions and when did it begin? what are the 2 hypothesis for why it happened?
Began about 14000 years ago - many Pleistocene animals went extinct
- mostly large-bodied
- Australia lost 15 of 16 large mammal genera
- other continents lost most of all large mammals
2 Hypothesis:
- climate change
- human overkill
Explain the climate change hypothesis for the Pleistocene extinctions
What are the problems with this hypothesis?
- glaciers retreated
- forests replaced grassland in NA and Eurasia
- southwestern US became semiarid
Problems:
- many species migrated and survived, why not large animals?
- why didn’t large animals go extinct during earlier interglacial periods?
- large herbivores went extinct at different times on different continents
Explain the overkill hypothesis for the Pleistocene extinctions
What are the problems with this hypothesis?
- idea is that humans killed off most of the large game in Australia, North America, South America, and Europe
- large animals appear to have died off immediately following human arrival
Problems:
- human populations were too small and had very simple weapons
- why kill more than you need?
- not very good evidence of hunting preserved in paleo/archaeological record > and fossils with evidence of butchering are from animals that are not extinct (ex. bison)
