1. The Paleozoic Era
Discussion of Geology (Movement of Land Masses), Biology (Evolution of Life Forms) and the Atmosphere
+ A special section on the Ediacaran Period

2. Learning Goals Students will:
Understand the geological, atmospheric and evolutionary changes that occurred during the Paleozoic Era.

3. Success Criteria
Students will show their understanding of learning goals by:
Explaining evidence to prove the major events that occurred during each geological period.

4. Evolution of Life Forms
Major life forms in each Era

5. Earth's Palaeogeography - Continental Movements through Time
This animation shows the movement of continents over time during the Paleozoic Era – this process is known as “Continental Drift”. We will learn more about this process in the next unit. The Continental crust is broken into plates which float on the viscous semi-molten Mantle. Convection of the Mantle causes the continental crust to move at a rate of about 5 to 10 cm a year.
Video:
Similar Video:
Spherical Video: (this is the best)

6. Setting the Stage
This era began with the break-up of the supercontinent of Rodinia.
The second Snowball Earth ended with the increase in volcanic activity related to the break-up of Rodinia
Increase in the Phosphorus cycle due to run-off from the now exposed continents
A warm, shallow sea began to form in the middle of it near the equator.
High oxygen and carbon dioxide levels were created and temperatures were warm. Oxygen levels in the atmosphere increased from 1% to as high as 20%

7. Rodinia – 650 million years ago

8. Ediacaran Time – 635 – 543 million years ago (Proterozoic Era)
When Charles Darwin wrote On the Origin of Species, he and most paleontologists believed that the oldest animal fossils were the trilobites and brachiopods of the Cambrian Period, now known to be about 540 million years old. Many paleontologists believed that simpler forms of life must have existed before this but that they left no fossils.

9. Ediacaran Biology
The Ediacaran marks the first appearance of multicellular life forms (believed originally to have formed in the Cambrian)
Many of these creatures are very unusual in their structure and have no known ancestors. (They belong to extinct Phyla).
Many trace fossils and soft bodied animals are found.
The animal fossil record from this era is sparse, possibly because animals had yet to evolve hard shells, which make for more robust fossils.
Three of the many interesting Ediacaran fossil animals. From the left are Tribrachidium, Cyclomedusa, and Dickinsonia.

10. Ediacaran Biology
The overwhelming majority of early multicellular life forms did not make it through the Ediacaran period. The few that did vanished within 5 million years. The first experiment in complex, multi-cellular life was over. But it laid the foundation for everything that followed.
It is suggested that the sudden Precambrian “boom” of life was triggered by a massive increase in deep-sea oxygen levels, and plenty of organic matter from the melting glaciers.
High oxygen levels led to the advent of collagen – which allows cells to bind together. Eventually cells were able to work together and
Recent measurement of oxygen levels over the past 600 million years suggests that oxygen may be the driving force for evolution. Periods of lower oxygen level have coincided with all the major mass extinctions, whereas land colonization occurred with rising levels.

11. Oxygen Levels and Extinctions

12. Cambrian Time – 543 – 488 million years ago (Paleozoic Era)
The Cambrian marked a step change in the diversity and composition of Earth's biosphere.
The Ediacaran biota suffered a mass extinction.
the Cambrian explosion saw the seemingly rapid appearance of representatives of all but one of the modern phyla.
There are even suggestions that some Cambrian organisms ventured onto land, producing trace fossils

13. Cambrian Biology
Almost all present day Phyla of life emerge during the "Cambrian Explosion“. It was given this name because of the relatively short time over which this diversity of forms appears.
The dominant life forms found in fossils are trilobites (went extinct at the end of the Permian) and brachiopods . The are hard shelled invertebrates.
The first fish appear – the jawless Ostracoderms (above), which filtered food from the mud.
The best Cambrian fossils are found in British Columbia’s Burgess Shale.
Trilobite
Brachipods
Burgess Shale organisms

14. Cambrian Geology Mean atmospheric O2 content over period duration
12.5 Vol % (63 % of modern level)
Mean atmospheric CO2 content over period duration
4500 ppm (16 times pre-industrial level)
Mean surface temperature over period duration
21 °C (7 °C above modern level)

15. Ordovician Time – 488 – 444 million years ago (Paleozoic Era)
During the Ordovician, most of the world's land — southern Europe, Africa, South America, Antarctica, and Australia — was collected together in the super-continent Gondwana.

16. Ordivician Biology
The number of corals, trilobites, nautiloids and brachiopods flourish in shallow warm seas.
The first jawed fish appear – the biological “arms race” begins.
Perhaps the most "groundbreaking" occurrence of the Ordovician was the colonization of the land. Remains of early terrestrial arthropods are known from this time, as are microfossils of the cells, cuticle, and spores of early land plants.

17. Ordivician Geology
Throughout the Ordovician, Gondwana moved towards the South Pole.
In the Lower Ordovician, North America roughly straddled the equator.
During the Middle Ordovician, uplifts took place in most of the areas that had been under shallow shelf seas.
Mean atmospheric O2 content over period duration
13.5 Vol % (68 % of modern level)
Mean atmospheric CO2 content over period duration
4200 ppm (15 times pre-industrial level)
Mean surface temperature over period duration
16°C (2°C above modern level)

18. The end of the Ordivician
The Ordovician came to a close in the second largest of the five major extinction events in Earth's history.
The most commonly accepted theory is that these events were triggered by the onset of an ice age that ended the long, stable greenhouse conditions typical of the Ordovician.
Glaciation locks up water from the world-ocean, causing sea levels to drop; the vast shallow intra-continental Ordovician seas withdrew, eliminating many ecological niches.
Much of Ontario is underlain by Ordivician, Silurian and Devonian limestone. We can see many outcrops as we drive towards Toronto – especially the Niagara Escarpment.
If you find a fossil between Toronto and Ottawa – it is of Ordivician age.

19. Ontario Geology
The Clappison’s Corners Road cut on Highway 6 heading into Hamilton and Highway 403

20. Silurian Time – 444 – 416 million years ago (Paleozoic Era)
In the Silurian, proto-Europe collided with North America
The collision folded coastal sediments that had been accumulating since the Cambrian off the east coast of North America and the west coast of Europe.
This event created the Appalachian Mountains which extend from Georgia (USA) to Newfoundland and into Greenland, Europe (Great Britain and Norway)
The Earth entered a long warm greenhouse phase, and warm shallow seas covered much of the equatorial land masses. Early in the Silurian, glaciers retreated back into the South Pole until they almost disappeared
Drying seas left behind the salt deposits along Lake Huron that are mined at Goderich.

21. Silurian Biology
Perhaps most striking of all biological events in the Silurian was the evolution of vascular plants (plants with vessels), which have been the basis of terrestrial ecology since their appearance.
In the oceans, there was a widespread radiation of crinoids, a continued proliferation and expansion of the brachiopods, and the oldest known fossils of coral reefs.
This time period also marks the wide and rapid spread of jawless fish, along with the important appearances of both the first known freshwater fish

22. Silurian Geology
During the Silurian, Gondwana continued a slow southward drift to high southern latitudes, but there is evidence that the Silurian icecaps were less extensive than those of the late Ordovician glaciation.
The southern continents remained united during this period.
Mean atmospheric O2 content over period duration
14 Vol % (70 % of modern level)
Mean atmospheric CO2 content over period duration
4500 ppm (16 times pre-industrial level)
Mean surface temperature over period duration
17°C (3°C above modern level)

23. Devonian Time – 416 – 359 million years ago (Paleozoic Era)
Well into the 20th century, the Devonian was often quoted as being "the age of fishes“. While the development of fishes is important, the name is now avoided, as fishes were but one of several important groups to see extensive development.
The period is named after Devon, a county in southwestern England, where Devonian outcrops are common.

24. Devonian Biology
The first fish evolved legs and started to walk on land as tetrapods around 365 Ma. Various terrestrial arthropods (including the first amphibians) also became well-established.
The Devonian seas were dominated by brachiopods and rugose corals, which built large reefs in shallow waters.
The first seed-bearing plants spread across dry land, forming huge forests. The first tree-like plants form forests allowing for shade and new ecological niches – including niches for the first land amphibians)
Primitive horsetails, club   mosses and 'tree-ferns'   (left) turn lifeless land into   new habitats for life.

25. Devonian Biology
In the oceans, primitive sharks became more numerous and the first lobe-finned and bony fish.
This period the first fish develop legs and move out of the sea to evolve into the first land animals (see next page on Tiktaalik)
The first appearance of insects – the planet’s most successful order of creatures. The first insects were wingless

26. Tiktaalik – Missing Link
Tiktaalik is the transition from fish to land animal (amphibian). The skeleton shows intermediate structures – a flat amphibian like head with a fish-like body and fins evolving into limbs

27. Devonian Geology
The Devonian period was a time of great tectonic activity, as Laurasia and Gondwanaland drew closer together.
Much of the land was desert with reddish sandstone sedimentary beds formed, made red by the oxidized iron ( hematite) characteristic of drought conditions.
Near the equator, Pangaea began to consolidate from the plates containing North America and Europe, further raising the northern Appalachian Mountains.
The deep, enormous Panthalassa (the "universal ocean") covered the rest of the planet.
Mean atmospheric O2 content over period duration
15 Vol % (75 % of modern level)
Mean atmospheric CO2 content over period duration
2200 ppm (8 times pre-industrial level)
Mean surface temperature over period duration
20 °C (6 °C above modern level)

28. Carboniferous Time – 359 – 299 million years ago (Paleozoic Era)
The term "Carboniferous" comes from England, in reference to the rich deposits of coal that occur there. These deposits of coal occur throughout northern Europe, Asia, and mid-western and eastern North America.
Oxygen level reach 35% allowing for the development of huge land animals. Giant ancestral dragonflies had wingspreads of 30 inches and bodies 15 inches in length.
Dense forests of seedless tress form across the land. Gymnosperms and Angiosperms had not yet evolved.

29. Carboniferous Biology
the amniote egg, which allowed for the further exploitation of the land by certain tetrapods. It gave the ancestors of birds, mammals, and reptiles the ability to lay their eggs on land without fear of desiccation.
A small group of creatures, cotylosaurs, gradually found new ways to sever their ties to rivers and ponds. From the cotylosaurs, an evolutionary intermediate between amphibians and reptiles, emerged the first true reptiles. These creatures were distinguished by their small size, agile limbs and the amniote egg.

30. Carboniferous Biology
Vast forests and swamps form
Amphibious tetrapods multiply wildly; many grow enormous in the high humidity and oxygen.
Giant insects and myriapods flourish in the high humidity and oxygen Plants develop bark, but bacteria not yet able to break it down. Dense layers of dead wood form coal beds.
Sea life dominated by sharks, corals, brachiopods, ammonoids, and foraminifera (tiny one celled creatures that we call plankton)
Arthropleurida (left)   was a giant centipede   in the Mississippian   swamps that could   grow up to 7 feet long.

31. Carboniferous Geology
the large expanse of ocean that covered the entire surface of the globe, except for a localized section where Pangaea, the massive supercontinent that existed during the late Paleozoic and early Triassic, was coming together.
Mean atmospheric O2 content over period duration
32.5 Vol % (163 % of modern level)
Mean atmospheric CO2 content over period duration
800 ppm (3 times pre-industrial level)
Mean surface temperature over period duration
14°C (0°C above modern level)

32. Permian Time – 299 – 251 million years ago (Paleozoic Era)
Mass extinction of marine life near the end of the Permian period - Groups made extinct include trilobites, sea lilies, and rugose corals. Other marine invertebrates severely affected. Fish are generally unaffected. According to recent investigation, the disaster that killed off almost 90% of all life on Earth about 251 MYA.
The period saw a massive desert covering the interior of the Pangaea, the large supercontinent that formed.
Glaciers covered much of Gondwanaland at the start of the Permian, as they had during the late Carboniferous.

33. Permian Biology
The first modern trees (conifers, ginkgos and cycads) appeared in the Permian
The environment became drier and hotter, reptiles thrived at the expense of amphibians.
the most successful insects were primitive relatives of cockroaches - about 90% of insects were cockroach-like insects.
Reptiles grew to dominance among vertebrates, because their special adaptations enabled them to flourish in the drier climate.
Hot dry conditions favor the   first modern trees, the   gymnosperms (left) such as   conifers, ginkos and cycads.   They spread with seeds   covered in a protective shell.

34. Permian Geology
During the Permian, all the Earth's major land masses except portions of East Asia were collected into a single supercontinent known as Pangaea.
Pangaea straddled the equator and extended toward the poles
Ocean currents moved around the single great ocean (Panthalassa = the universal sea), and the Paleo-Tethys Ocean, a large ocean that was between Asia and Gondwana.
Mean atmospheric O2 content over period duration
23 Vol % (115 % of modern level)
Mean atmospheric CO2 content over period duration
900 ppm (3 times pre-industrial level)
Mean surface temperature over period duration
16°C (2°C above modern level)

35. The Permian Extinction
The Permian ended with the most extensive extinction event recorded in paleontology: the Permian-Triassic extinction event. 90% to 95% of marine species became extinct, as well as 70% of all land organisms. On an individual level, perhaps as many as 99.5% of separate organisms died as a result of the event.
Massive flood basalt eruptions with magma outputs lasting thousands of years in what is now the Siberian Traps contributed to environmental stress leading to mass extinction. Enough carbon dioxide from the eruptions was produced to raise world temperatures five degrees Celsius (alone this is not enough to kill off 95% of life)

36. Siberian Flood Basalt Theory

37. Siberian Flood Basalt Theory
The Permian-Triassic transition appears in this rock outcrop in Shangsi, China. Researchers have dated volcanic crystals from before and after the mass extinction, pinning the blame for the giant extinction on massive volcanic activity.

38. The Permian Extinction
An additional hypothesis involves ocean venting hydrogen sulfide gas. Portions of deep ocean will periodically lose all of its dissolved oxygen allowing bacteria that live without oxygen to flourish and produce hydrogen sulfide gas. If enough hydrogen sulfide accumulates in an anoxic zone, the deadly gas can rise into the atmosphere.

39. The Permian Extinction
Another hypothesis builds on the flood basalt eruption theory. Five degrees Celsius would not be enough increase in world temperatures to explain the death of 95% of life.
But such warming could slowly raise ocean temperatures until frozen methane reservoirs below the ocean floor near coastlines (a current target for a new energy source) melted, expelling enough methane, among the most potent greenhouse gases, into the atmosphere to raise world temperatures an additional five degrees Celsius.
The frozen methane hypothesis helps explain the increase in carbon-12 levels midway into the Permian-Triassic boundary layer.

40. Evolution and Abundance of Large Animals in the Paleozoic and Mesozoic

41. Video Summary
Geo logic History of the Earth Part 1:
Nova: Permian Extinction: