Diff. Geoscience
Geological Eras, Paleozoic
Chapters 22,23 pages 601 to 617
Name:
Period:
The early Paleozoic, Cambrian period
1.
Laurentia would later become the North American continent.
Where was Laurentia located on the globe?
2.
What was the main geographical feature of Laurentia?
3.
What types of sedimentary rock were being formed?
4.
Where did the calcium carbonate in the limestone come from?
5.
Why is Sandstone deposited at the highest level, then Shale, and finally Limestone at the lowest level?
6.
What does it mean about sea levels if the sandstone deposits move further inland?
The Cambrian explosion of life introduced many new species.
Modern arthropods include insects, spiders, centipedes, shrimp, and crayfish.
Polychaetes are known by many names: lugworms, clam worms, bristleworms, fire worms, palolo worms, sea
mice, featherduster worms, etc., but all possess an array of bristles on their many leg-like parapodia -- the name
polychaete, in fact, means "many bristles". The many common names reflect the wide array of body forms
found in this group, unlike the earthworms and leeches which all have the same general appearance.
Brachiopods are another distinct Cambrian animal form. The evolutionary lineage of the Brachiopods appears
to begin with a creature called Halkieria evangelista from the Sirius Passet formation of Greenland which is
about 525 million years ago.
Why????
The most fundamental question about the Cambrian Explosion is why did it happen. There are many ideas, and
of course it is possible that more than one of these effects worked together.
A. Climate Change - It appears that the period prior to the Cambrian era was marked by very cold temperatures.
In fact, a somewhat controversial theory, termed "Snowball Earth," claims that there was so much ice that much
of the sun light was reflected and we came close to entering an irreversible downward spiral in temperature as
less and less of the sun's energy was absorbed by the surface of the planet. Thus, the Vendian/Ediacaran life
forms would have been contending with very unfavorable conditions. Under this theory, the seeds of the
Cambrian Explosion were planted during this earlier period, and when there were vast new possibilities for life
in new and more favorable conditions, an explosion of new life forms occurred to fill these new niches.
B. Development of Predators - PreCambrian fossils show little evidence for predators. Clearly, predators were
prevalent and highly dangerous to Cambrian life. Evolution responds to challenge. Predators require many
adaptations to find their prey - ability to move rapidly toward a target without losing track of it, hunting
strategies, grasping the prey - all of which would also lead to development of brains and advances in nervous
systems. The necessity to fend off predators to survive would have also triggered a great acceleration in the rate
of evolutionary change in other animals, including the development of protective outer armor (shells, or the
scale-like structures and spines of the Wiwaxia).
C. Evolutionary Breakthrough - Perhaps some new feature developed by chance during evolution of the
precambrian life forms that provided a huge advantage. An example would be the development of an
exoskeleton that would provide rigidity against which muscles could work, making it suddenly advantageous
for complex animals to develop.
D. Changes in Ocean Chemistry or in Geography - The Cambrian occurred at the time plate tectonics were
breaking up a super-continent, and also at a time when a large amount of phosphorus was being deposited on
the shallow undersea shelves surrounding the continents. Phosphorus is an essential ingredient for life. Another
twist is that the phosphorus was to abundant that animals had to fight being poisoned by depositing it into
shells. Or perhaps some other chemical or geographical change helped trigger the explosion.
E. Rapid Climate Fluctuations - Marine sediments show 10 large oscillations during the Cambrian period in the
amount of carbon 13, which we think indicates a series of global extinctions and recoveries. Perhaps the
challenges of adapting to such a rapidly changing environment produced a period of evolutionary
breakthroughs.
7.
What types of marine life left the clearest fossils in the clay that became shale?
8.
Look up Burgess shale on the Internet and write a paragraph describing one of the creatures found
fossilized in the deposit.
The middle Paleozoic, Ordovician to Mississippian periods
9.
How do coral reefs form?
10.
Why do minerals deposit faster in lagoons than in open seas?
11.
What are the gypsum and halite deposits mined from ancient lagoons used for today?
12.
Name two sets of mountains formed by plate collisions in the Taconic, Caledonian, and Acadian
Orogeny.
13.
The fishes and eels of the period had internal skeletons of cartilage. How is cartilage different than true
bone? (Hint: your nose and ears are made of cartilage)
14.
What did the growth patterns of the coral tell amount the length of Earth days during the Paleozoic as
compared to the day length now?
15.
When did plants develop the ability to produce seeds?
16.
Why did plants have to develop vascular tissue and seeds to survive on land?
17.
What caused the extinction of many marine species in the late Ordovician period?
18.
A thermocline is a boundary between cold oxygen poor water at the bottom of a lake or ocean and the
warm oxygen rich water at the top.
How did the inversion of the two layers in the late Devonian period effect the coral population?
What rock layer supports the theory of reduced oxygen supply in the water?
The late Paleozoic, Pennsylvanian and Permian periods
19.
Give two reasons why did coal deposits not form until after the Mississippian period.
20.
Why did sea levels fluctuate so radically during the Pennsylvanian era?
21.
The federal government is planning long term storage of high level radioactive wastes in Yucca
Mountain Nevada. What characteristics of the large salt deposits of the Permian Reef Complex make it suitable
for storage of nuclear waste?
22.
How did the Permian Reef Complex store oil in west Texas?
23.
How did the Ancestral Rocky Mountains form?
24.
Crinoids were very abundant during the late Paleozoic periods. How did Crinoids feed?
25.
Fish with thick bones in their lobe fins like the lungfish above were able to walk on land for short
periods of time. What general species did these fish evolve into?
26.
Describe the plants and animals that made up the coal swamps.
The End of The Permian Period
The corals were not the only species to become extinct. The Permian Extinction was largest mass extinction that
had ever occurred. No extinction since has killed so much of the life on the planet. In the seas, 90 to 95 percent
of the species went extinct or were severely harmed. On land the damage was less severe, but some species, like
the pelycosuars, died out completely.
Mass Extinction Theories
Volcanic Activity
There are many theories about the cause of the Permian extinction. It could have been caused by huge amounts
of volcanic activity, more than any that has been experienced since written history. We know from recent
volcano eruptions that large eruptions can cause the temperature to drop all around the globe.
Comets and Meteors
Another theory is that a comet or meteor could have hit the planet, setting off a series of events that would have
caused changes to temperature and sea levels, including the formation of glaciers. Others think that the
formation of a land mass as huge as Pangea upset the balance of climate that happens when the ocean waters
can affect more of the land surface.
No matter what the cause, the extinction event that took place at the end of the Permian Period was so important
that it brought the end to the Paleozoic Era. Life on Earth would never again look as it had during the Paleozoic
Era.
27.
Why would volcanic activity or Meteor impacts cause a large drop of temperature over large areas of the
earth?