Transcript of The Age of Mammals. Setting the Stage The Cenozoic follows the Cretaceous (K-T) extinction that...
- Slide 1
- The Age of Mammals
- Slide 2
- Setting the Stage The Cenozoic follows the Cretaceous (K-T)
extinction that caused dinosaurs to go extinct. The planet was
dominated by relatively small mammals, birds, reptiles, and
amphibians. It did not take long for mammals and birds to greatly
diversify in the absence of the large reptiles that had dominated
during the Mesozoic. Some birds grew larger than the average human.
This group became known as the "terror birds," and were formidable
predators. Mammals came to occupy almost every available niche
(both marine and terrestrial), and some also grew very large,
attaining sizes not seen in most of today's terrestrial
mammals.
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- Arrangement of Continents At the beginning of the Cenozoic,
most of continents had separated into their present form. Australia
had yet to separate from Antarctica and India had yet to collide
with Asia.
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- Geology of the Cenozoic During the Cenozoic, the continents
move into their current positions. Australia-New Guinea, having
split from Pangaea during the early Cretaceous, drifted north and,
eventually, collided with South-east Asia Antarctica moved into its
current position over the South Pole 65 million years ago 35
million years ago 50 million years ago
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- Geology of the Cenozoic The Atlantic Ocean widened and, later
in the era, South America became attached to North America via the
isthmus of Panama. India collided with Asia 55 to 45 mya and
created the Himalayan Mountains. Arabia collided with Eurasia,
closing the Tethys ocean, around 35 mya. 20 million years ago
Present day 50 thousand years ago
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- Cenozoic Video https://www.youtube.com/watch?v=ApsCGttW2Us (Age
of Mammals - Global Processes 3:11)
https://www.youtube.com/watch?v=ApsCGttW2Us
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- Estimated Global Temperatures in the Cenozoic Eon
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- Cenozoic Climate Trends Climate trends are closely related to
the geological map. The PaleoceneEocene Thermal Maximum (PETM) of
55.8 mya was a significant global warming event However, since the
Azolla event of 49 mya, the Cenozoic Era has been a period of
long-term cooling. After the tectonic creation of Drake Passage,
when South America fully detached from Antarctica during the
Oligocene (a geologic epoch of the Paleogene period and extends
from about 33.9 to 23 mya), the climate cooled significantly due to
the advent of the Antarctic Circumpolar Current which brought cool
deep Antarctic water to the surface.
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- Cenozoic Climate Trends The cooling trend continued in the
Miocene, with relatively short warmer periods. When South America
became attached to North America creating the Isthmus of Panama,
the Arctic region cooled due to the strengthening of the Humboldt
and Gulf Stream currents, eventually leading to the glaciations of
the Quaternary ice age, the current interglacial of which is the
Holocene Epoch.
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- Renaming the Tertiary Tertiary is the former term for the
geologic period from 66 million to 2.58 million years ago, a time
span that lies between the unused Primary period (Proterozoic) and
Secondary period (Paleozoic) and the Quaternary. The Tertiary is no
longer recognized as a formal unit by the International Commission
on Stratigraphy, but the word is still widely used. The Tertiary
has been divided between the Paleogene and Neogene Periods and the
first stage of the Pleistocene epoch.
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- Paleogene The Paleogene (informally Lower Tertiary) comprises
the first part of the Cenozoic Era. Lasting 43 million years, the
Paleogene is most notable as being the time in which mammals
evolved from relatively small, simple forms into a large group of
diverse animals in the wake of the K-T extinction event that ended
the preceding Cretaceous Period. Time 66 - 23 million years ago
(Cenozoic Era)
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- Paleogene Geology The continents during the Paleogene continued
to drift closer to their current positions. India was in the
process of colliding with Asia, subsequently forming the Himalayas.
The Atlantic Ocean continued to widen and Africa was moving north
to meet with Europe and form the Mediterranean South America was
moving closer to North America (they would later connect via the
Isthmus of Panama). Inland seas retreated from North America early
in the period. Australia had also separated from Antarctica and was
drifting towards Southeast Asia. Mean atmospheric O2 content over
period duration ca. 26 Vol % (130 % of modern level) Mean
atmospheric CO2 content over period duration ca. 500 ppm (2 times
pre- industrial level) Mean surface temperature over period
duration ca. 18 C (4 C above modern level)
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- Paleogene Climate Early in the Cenozoic, the Paleocene-Eocene
Thermal Maximum (PETM) occurred - this period of global warming was
due to methyl hydrates being released from marine sediments. With
the exception of the PETM, a cooling and drying trend (relative to
the Mesozoic) occurred throughout the Paleogene, a trend that
persists today. The trend was partly caused by the formation of the
Antarctic Circumpolar Current, which significantly cooled oceanic
water temperatures.
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- Paleogene Climate The major changes in the oceanic and
atmospheric circulation and led to the extinction of numerous
marine life and a major turnover in mammals. Modern rain forests
and grasslands appeared. Grasses, an angiosperm, evolved in the
Paleogene promoting the evolution of a variety of large
grass-eating herbivores like horses, cattle, deer, etc.
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- Paleogene Biology Mammals began to take advantage of the niches
left empty by the extinction of the dinosaurs, evolving into many
new species. However, mammals were not the dominant predators in
the early Paleogene - a group of terror birds, large flightless
birds are found in the fossil record. Prosimians, insectivorous
early relatives of true primates can be found. The largest mammal,
Pantolambda (a primitive plant eater), was about the size of a
small pony. Rodents appeared late in the Paleocene epoch of the
Paleogene.
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- Paleogene Biology Although the majority of Cretaceous plant
species did not survive into the Paleocene, ferns were very
abundant for a brief period following the end- Cretaceous asteroid
impact. Subsequently, flowering plants and conifers once again
became more abundant during the early Paleocene. The marine world
of the Paleocene was much more like the modern marine realm than
that of the Cretaceous. Sharks ruled in the absence of Mesozoic
marine predatory reptiles The cooling trend meant that polar ice
caps developed as well as tropical forests and grasslands.
Temperate forests with seasons produced the mixed deciduous forest
we see today. Cooling temperature produced vast grasslands which
supported large grazing herbivores.
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- Paleogene Megafauna This period produced very large birds, the
largest land mammals ever seen on the planet (Paraceratherium, see
below), the evolution of whales, massive snakes (Titanoboa), and
large predators.
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- Neogene The Neogene covers about 20 million years. During this
period, mammals and birds continued to evolve into roughly modern
forms, while other groups of life remained relatively unchanged.
Early hominids, the ancestors of humans, appeared in Africa. The
global climate cooled considerably over the course of the Neogene,
culminating in a series of continental glaciations in the
Quaternary Period that follows. Time 23 - 2.3 m.y.a (Cenozoic
Era)
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- Neogene Geology Some continental movement took place, the most
significant event being the connection of North and South America
at the Isthmus of Panama. This cut off the warm ocean currents from
the Pacific to the Atlantic ocean, leaving only the Gulf Stream to
transfer heat to the Arctic Ocean.
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- Neogene Geology The Neogene Period was a time when the
continents were crashing into each other. Mountains pushed up in
many places. India continued its push into Asia further raising the
Himalayan Mountain Range. Italy moved north into Europe raising the
Alps. Spain crashed into France to form the Pyrenees. The Rocky
Mountains and the Andes Mountains formed in North and South America
during this time.
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- Neogene Sea levels Sea levels were lower due to the effects of
cooling temperatures and continental collision. The North and South
Poles began to have ice caps. During the Neogene Period, the polar
ice thickened and took up more space in the ocean. The new
mountains trapped water as snow and ice. All of this ice formation
caused sea levels to drop even more. The drop in sea levels opened
up land bridges between continents. This allowed animals to migrate
between continents.
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- Neogene Geology Summary The continents in the Neogene were very
close to their current positions. The isthmus of Panama formed,
connecting North and South America. The Andes began to rise. India
continued to collide with Asia, forming the Himalayas. Sea levels
fell, exposing land bridges between Africa and Eurasia and between
Eurasia and North America. The global climate became seasonal and
continued its overall drying and cooling trend which began in the
beginning of the Paleogene. The ice caps on both poles began to
grow and thicken, and by the end of the period the first of a
series of glaciations of the current Ice Age began. Mean
atmospheric O2 content over period duration ca. 21.5 Vol % (108 %
of modern level) Mean atmospheric CO2 content over period duration
ca. 280 ppm (1 times pre- industrial level) Mean surface
temperature over period duration ca. 14 C (0 C above modern
level)
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- Neogene Biology In response to the cooler, seasonal climate,
tropical plant species gave way to deciduous ones and grasslands
replaced many forests. Grasses therefore greatly diversified, and
herbivorous mammals evolved alongside it, creating the many grazing
animals of today such as horses, antelope, and bison.
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- Neogene Biology South America moved to the north. By the
Pliocene Epoch it merged with North America forming the Isthmus of
Panama. Armadillos, porcupines, ground sloths and opossums migrated
from South America to North America. Dogs, cats, bears, and horses
from North America crossed into South America.
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- Neogene Biology The climate continued to cool. Many of the
areas that had been covered by forests were changing to grasslands.
Grasses were better suited to the cool dry weather. But grasses had
less nutrition than the forest plants of the Paleogene Period. It
took more effort to get the nutrients out. Grasses were made of
chemicals that were hard on teeth. Chewing wore the teeth down.
Animals that ate grasses needed stronger teeth. Other animals
developed new ways to digest the grasses inside their bodies. These
animals had more than one stomach. They are called ruminants. They
were efficient at getting nutrients from the grasses. This new type
of animal, the artiodactyl, developed into many familiar species:
camels, bison, sheep and giraffes, to name a few. The grazing
animals could run fast. Predators had to adapt or go hungry. The
sleek bodies of the dog and cat carnivores were able to run fast
and use their powerful jaws and teeth to take down their prey.
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- Neogene Megafauna & Extinction The Megafauna
(meg-UH-fawn-UH) or "big animals" were the large animals that lived
during the late Cenozoic Era after the extinction of the dinosaurs,
mostly during the last Ice Age. They included animals such as the
Woolly Mammoth, Smilodon (sabre-toothed cat), Megatherium (Giant
ground sloth) and other large herbivores Most were very large and
often hairy, having a long, thick, mammoth-like fur coat covering
nearly their entire bodies to protect themselves from the cold.
They all went extinct in the geological blink of an eye around
10,000 years ago for reasons not quite known. Some suspect it was
early man, which appear in the fossil record when the Megafauna
started to go extinct. https://www.youtube.com/watch?v=iaCIkiZLK ig
(Extinction of the Smilodon)
https://www.youtube.com/watch?v=iaCIkiZLK ig
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- Quaternary The term Quaternary ("fourth") was proposed in 1759
for alluvial deposits in northern Italy. It was introduced in 1829
for sediments of France's Seine Basin that seemed clearly to be
younger than Tertiary Period rocks. The Quaternary Period follows
the Neogene Period and extends to the present. The Quaternary
covers the time span of glaciations classified as the Pleistocene,
and includes the present interglacial period, the Holocene. This
places the start of the Quaternary at the onset of Northern
Hemisphere glaciation approximately 2.6 million years ago. Prior to
2009, the Pleistocene was defined to be from 1.805 million years
ago to the present, so the current definition of the Pleistocene
includes a portion of what was, prior to 2009, defined as the
Pliocene. Time 2.6 million years ago to the present (Cenozoic
Era)
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- Quaternary Time 2.3 million years ago to the present (Cenozoic
Era) Subdivisions of the Quaternary System System/ Period Series/
Epoch Stage/ Age Age (Ma) Quaternary Holocene0.0117-0 Pleistocene
Tarantian0.126-0.0117 Ionian0.781-0.126 Calabrian1.80-0.781
Gelasian2.58-1.80 NeogenePliocenePiacenzianolder
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- Quaternary Geology The 2.6 million years of the Quaternary
represents the time during which recognizable humans existed. Over
this short time period, there has been relatively little change in
the distribution of the continents due to plate tectonics. The
Quaternary geological record is preserved in greater detail than
that for earlier periods. The major geographical changes during
this time period included the emergence of the Strait of Bosphorus
and Skagerrak during glacial epochs, which respectively turned the
Black Sea and Baltic Sea into fresh water, followed by their
flooding (and return to salt water) by rising sea level The
periodic filling of the English Channel, forming a land bridge
between Britain and the European mainland The periodic closing of
the Bering Strait, forming the land bridge between Asia and North
America.
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- Quaternary Climate The climate was one of periodic glaciations
with continental glaciers moving as far from the poles as 40
degrees latitude. During this time, substantial glaciers advanced
and retreated over much of North America and Europe, parts of South
America and Asia, and all of Antarctica. The Great Lakes formed and
giant mammals thrived in parts of North America and Eurasia not
covered in ice. Artist's impression of Earth during the Last
Glacial Maximum
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- Quaternary Biology During the Quaternary period, mammals,
flowering plants, and insects dominated the land. There was a major
extinction of large mammals in Northern areas at the end of the
Pleistocene Epoch. Many forms such as saber-toothed cats, mammoths,
mastodons, glyptodonts, etc., became extinct worldwide. Others,
including horses, camels and American cheetahs became extinct in
North America. These mammals became extinct when the glacial period
Age ended about 11,700 years ago. This extinction coincides with
the arrival of humans into North America from Asia. Modern humans
evolved about 190,000 years ago Northern Hemisphere Ice Age during
the Quaternary.
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- The Holocene The Holocene is the name of the epoch that we live
in today. It started 11,700 years ago with the end of the last
glaciation. Climatologists believe we are living in an interglacial
period that will end with onset of a new ice age. There have been
minor warm and cool periods in the Holocene. The impact of modern
industrial society is affecting the atmosphere and may have an
impact on the climate in the future. Pre-industrial CO2 levels were
about 230 ppm, today we have exceeded 400 ppm.
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- Cenozoic Videos https://www.youtube.com/watch?v=eObjVCFv-IM
(The North American Ice Age : Documentary on How Ice Created North
America (44:07)) https://www.youtube.com/watch?v=eObjVCFv-IM
https://www.youtube.com/watch?v=eY-ltUIsnrQn (The 6 th extinction)
(9:17) https://www.youtube.com/watch?v=eY-ltUIsnrQn
https://www.youtube.com/watch?v=7QY-FY9nz-M (The Holocene
Extinction) https://www.youtube.com/watch?v=7QY-FY9nz-M