Precambrian Era

Archean

Proterozoic

Precambrian Era: IntroductionLasted a very long time (4.6 billion years)This era ended 540 million years agoIt is 88% of the earth’s historyDivided into two subdivisions: Archean

and ProterozoicEarth’s crust just began to solidifyFossils are rare in Precambrian rocks

because the animals were soft bodied

Major Changes during the era:

1. Formation of sun (light)2. Creation of the earth3. Creation of the atmosphere (through

volcanic eruptions) volcanoes release many gases, which are valuable in the atmosphere

4. Creation of oceans5. Creation of life the first living organisms

have been found to come from this era

Archean

This name was given to the period of earth forming

Lasted 2.8 billion yearsTemperature at first was hot, no ocean,

alot of volcanic activityBy 3.8 billion years the first living things

inhabited earth called: Archaea Allowed us to discover that living things

produce oxygen

ProterozoicThis period began 2.5 billion years agoThe three major subdivisions of his period

are: neoproterozoic, mesoproterozoic and paleoproterozoic

The time when stable continents appearedMany fossils come from this time periodThis period showed the first evidence of

oxygen build up in the atmosphere

Life begins:

The first life forms were extremely simple and undeveloped these organisms were blind, brainless, soft bodied and no hard skeleton

i.e. jelly fish, sea worms and bacteriaFossils show stromatolites (reeflike deposits)

produced by cynobacteria this indicated earth was covered in shallow water since the beginning of time.

Stromatolites were abundant in the Archean but began to decline in the Proterozoic

Paleozoic Era

CambrianOrdovician

Silurian

Paleozoic Era

DevonianCarboniferous

Permian

Time ScaleERA PERIOD EPOCH BEGAN

(millions of

years) PALEOZOIC

Permian 290Carboniferous Pennsylvania

n 323Mississippian 354

Devonian 417Silurian 443Ordovician 490Cambrian 540

Paleozoic OverviewThe Paleozoic era lasted about 300 million

yearsAt the beginning of this era the land

masses were scattered about the earth’s oceans but by the end they had come together to form Pangaea

Paleozoic rocks contain an abundance of fossils allowing scientists to divide the era into 7 periods

The increased fossils is a result of an increase in plant and animal life at the beginning of the Paleozoic Era

Cambrian

Due to a variety of warm shallow seas covering most of the continents, marine invertebrates dominated the world.

The most common invertebrates were trilobites, hard-shelled animals that lived on the ocean floor.

Brachiopods also inhabited the landscape in large numbers during this period.

Other forms of invertebrates include worms, jelly-fish, snails and sponges

Brachiopods such as snails, clams and mollusks became the dominant life-forms.

Graptolites, colonies of invertebrate animals, flourished during this time.

A primitive fish also appeared during this era, the ostracoderm

The fossils of the ostracoderm are the oldest fossils of vertebrates

During the Precambrian, Cambrian and Ordovician times there were no land plants, only marine plant life.

Ordovician

Silurian

Echinoderms, relatives of modern sea stars became common in this period

Coral also started to grow in this timeA special scorpion-like sea creature

roamed the sea floors during this timeThese eurypterids were nearly 2.7m in

lengthDuring the end of this period the earliest

land plants, as well as spiders and millipedes developed.

DevonianAlso known as the age of fishes the Devonian

period is characterized by its many types of fish

From lungfish to rhipidistians bony fish inhabited the waters.

Lungfish could breathe air and rhipidistians had strong fins which enabled them to walk on land for short periods of time.

The first amphibian, Ichthyostega, resembled a large salamander evolved from these fish and is thought to be the ancestor of frogs and toads.

Land plants such as horsetails, ferns, and cone-bearing plants developed.

Carboniferous

MississippianPennsylvanianClimate was warm, with high humidity, and a

variety of forests and swamps.Major rock deposits, as well as oil deposits and

coal deposits are thought to be formed during this period.

Amphibians and fish continued to flourish.Crinoids, other relatives of sea stars were

common.Insects such as giant cockroaches and

dragonflies were common on land.Near the end of this period the first vertebrates

adapted to life on land, they resembled large lizards.

Permian

Marking the end of the Paleozoic era there was a mass extinction of many life-forms.

Pangaea was formed.Due to plate tectonics, mountain ranges

appeared causing deserts and dry savanna climates.

The shallow seas evaporated resulting in the extinction of trilobites and eurypterids.

However, reptiles and amphibians were able to survive into the Mesozoic Era.

CENOZOIC ERA

Cenozoic Era: Introduction65 million years ago to todayAlso known as age of mammals (because they

became the most dominant life form)Increased tectonic activity creating huge

mountain ranges i.e. The Alps or the HimalayasDivided into two periods: Quaternary and

Tertiary as well as seven epochsThis era with stood the last Ice age

(Quaternary period) Climate was originally warm and humid but cooled gradually

This period is now divided into five epochs (from most recent to latest)

1. Pliocene - large carnivores- dogs, bears, etc. Are abundant

2. Miocene - grazing herds abundant, raccoons and wolves appear

3. Oligocene – deer, pigs, horses, camels, cats and dogs appear

4. Eocene – early horses, flying squirrels, bats and whales

5. Paleocene – age of mammals begins In this period approx. 50% of all plant and animals

form previous years became extinct and new animals adapted

Tertiary

This period includes the ice age to present day

Divided into two more subdivisions(in order of most recent):

1. Holocene – complex human societies and end of the last ice age

2. Pleistocene – wolly mammoths, rhinos and humans begin to appear

Quaternary

Ice Age (aka Glacial period)The growth of the ice began 120,000 years ago

however the largest extent of the ice age was 18,000 years ago

The oceans cooled substantially and ice began to cover the Northern Hemisphere

The sea levels fell as the ice sheets spreadThe ice ages that have occurred over the last 2

million years have effected the landscape in North America

Ice Age’s peak is when 32% of Earth was covered in ice over a thousand feet thick

Many animals from the ice age are extinct for example: mammoths, snowshoe hare, musk ox and many more

Evolution of Man:

http://www.youtube.com/watch?v=faRlFsYmkeY&feature=related 

Oldest fossil of hominids (very similar to homo sapiens) is 6 million years old

During the Pliocene the first hommoids were upright (modern limb proportions)

The first evidence of homo was in AfricaHumans were extremely diverse, could

adapt to change and ate what the dinosaurs did

Species Time Period

Ardipithicus ramidus 5 to 4 million years ago

Australopithecus anamensis 4.2 to 3.9 million years ago

Australopithecus afarensis 4 to 2.7 million years ago

Australopithecus africanus 3 to 2 million years ago

Australopithecus robustus 2.2 to 1.6 million years ago

Homo habilis 2.2 to 1.6 million years ago

Homo erectus 2.0 to 0.4 million years ago

Homo sapiens archaic 400 to 200 thousand years ago

Homo sapiens neandertalensis 200 to 30 thousand years ago

Homo sapiens sapiens 200 thousand years ago to present

Presentation Summary: The earth began about 4.6 billion years ago The time scale is divided into 4 eras: Precambrian,

Paleozoic, Mesozoic, and Cenozoic Precambrian era consists of the formation of the earth, as

well as formation of the continental shields, and bacteria are the most common form of life.

The Paleozoic era consisted of mainly invertebrate marine life at the beginning, moving onto vertebrates and early land life forms.

Pangaea was formed late in the Paleozoic, early in the Mesozoic era where dinosaurs and large reptiles ruled the earth, as well as the first sign of flowering plants.

Cenozoic ear was the first age of mammals. Early horses, squirrels, cats, dogs and large carnivores appear. Most importantly humans and human societies began after the last ice age.

Questions:

1. Why are fossils rare in Precambrian rocks?2. How did the Ice Age affect animal life in the

Cenozoic era?3. What are the three main divisions of

geologic time?4. What era is also known as the age of

reptiles?5. How long ago did the Precambrian era end?6. In what era is the Pangaea theory from?

Work Cited: Bergman, Jennifer. “An Overview of Earth’s History.” Windows to

the Universe. 23 Aug. 2009. 8 Feb. 2010.<http://www. windows.ucar.edu/tour/link=/earth/past/geologic_time.html>.

“Cenozoic.” February 9th, 2010. <http://fossils. valdosta.edu/era_cenozoic.html>.

“Precambrian Era.” Kinder Science. 8 Feb. 2010 <http://www.kinderscience.com/precambrian_era.htm>.

Sager, Ramsey, Phillips and Watenpaugh. Modern Earth Science. Austin. Holt, Rinehart and Winston, 2002.

Safra, Jacob. “Geochronology” The New Encyclopaedia Britannica. 19th e.d: 2008.

“The Story of Lucy.” Long Foreground. 2010. Washington State University. March 10th, 2010.<http://www.wsu. edu.8001/vwsu/gene/learn-modules/top_longofr .html>.

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