Eras of Earth’s History

EQ: What causes changes in the Earth? How does knowing the past give us a VISION for the future?

Precambrian Time Eon

Precambrian Time Eon

4.6 billion years ago-545 million years ago Information about this time on Earth is

SCARCE Rocks are buried deep within Earth’s Crust Information on rocks damaged or destroyed by

Earth’s inner heat and pressure of other rock layers

Moon forms during this time

Precambrian Eon continued….

Earth originally thought to be “dead”

Volcanoes produce toxic atmosphere

Water and water Vapor that form the oceans comes from volcanoes, asteroids and comets!!!

*Precambrian Eon continued….*

Closer look at rocks show Signs of cynobacteria

Cynobacteria-changed Earth’s past atmosphere of water vapor, ammonia and methane into Nitrogen and Oxygen: STILL FOUND ALIVE TODAY in deep sea Thermal Vents and in volcanoes

Today’s atmosphere made up of nitrogen , oxygen and water vapor

Phanerozoic Eon (3 Eras)

*Paleozoic Era: 545-245m.y.a.: Basic Traits*

The longest of all the Eras on the Earth

Contains 7 periods Fossils of large organisms first found

in this era Almost all are marine environment Largest land Continent called

Gondwana (begins with 90 % of Earth’s surface covered by water)

Warm Earth; Life limited to oceans; ozone layer not fully developed: no plants on land intially

Ends with the largest mass extinction in Earth’s history (90% of all life killed)

*Why did life first start in the ocean?* More stable environment:

Water 22x heat capacity than air

UV Protection: – DNA Damaged by UV

radiation

– DNA contains all information for life

– Earth’s ozone layer just starting to develop from oxygen produced by cynobacteria

*Why did life first start in the ocean?* Gravity’s affect

neutralized -organisms would

develop in environment in which gravity would have no impact on animal’s structure– NO need for powerful

muscles to move

*Why did life first start in the ocean?* Easier to obtain

minerals and gases necessary for life

Water naturally has these items dissolved in it

Organisms could just absorb materials as water passed by

*Easier to obtain food*

Food would be suspended in 3 dimensions: filter feeding or feeding with tentacles become popular

7 periods of Paleozoic Era

Cambrian Period (545-505) – Trilobites

– Clams

– Inland seas suggest warm Earth

– Land Formation: supercontinent Gondwana; (S hemisphere)

Ordovician Period (505-438) First land plants (ferns) First vertebrates: early

fish appear Life moves into shallower

water: Suggests ozone layer almost fully developed as life moves closer to land

Laurussia seperates from Gondwana

Silurian Period (438-408) Corals Dominate World’s

Oceans Warm Earth Plants move further inland Animals now moving

further inland by way of water; fresh water fish

N. America covered by shallow sea

*Devonian Period (408-360)*

Fish dominate oceans First amphibians Signs of Earth

beginning to cool: Water retreats forcing organisms to adapt to the new changes. More land created

Mississippian Period (360-320) Amphibians dominate

land life Earth much cooler as

glaciers move southward from polar regions

Cooler Earth forces Amphibians to adapt to changes; (less water-thicker skin)

Pennsylvanian Period (320-286)

First reptiles and insects

Shallow seas over N.America almost disappeared

Cooler Earth

*Permian Period (286-245)*

Glaciers retreat Earth Warming back up Ends with largest mass extinction in fossil

record (Asteroid impact)

*Mesozoic Era *

AGE OF DINOSAURS 245-65 Million Years Ago Split into 3 major periods Triassic period (245-208 million years) Jurassic Period (208-144 million years) Cretaceous Period (144-65 million years)

Triassic Period

Marks beginning of Mesozoic Era First dinosaurs and mammals appeared

around 225 million years ago Atlantic Ocean Pangaea breaks up Flowering Plants appear Eoraptor, Plateosaurus and Teratosaurus

*Why Dinosaurs Evolve*

Environmental Factors- As Pangaea break apart each land mass gets a unique climate

Disease Influence- Diseases possible reason species die out

Competition for Food- organisms compete for same food sources; winners live losers die

Predatory Influence- animals develop defenses against Predators

Jurassic Period (208-144)

Flowering Plants and Dinosaurs dominate land Birds appear Appalachian Mountains Form Dinosaurs become more diverse from basic shapes Allosaurus Stegosaurus Diplodicus Ceratosaurus

Cretaceous Period (144-65)

Most advanced dinosaurs: Highly specialized, most successful of all dinosaur species

Modern Earth Appears Ends in Mass Extinction of Dinosaurs Tyrannosaurs, Tricerotops, Ankylosaurus,

Protocerotype, Velocoraptors, Pterodactyl

*Meteorite Theory?*

Says that asteroid/comet 3-5 miles wide struck near Yucatan Peninsula and caused Dinosaur Extinction

Iridium deposits in KT layer help support this

However, closest Dinosaur bones ever found date about 1,000 prior to event

Climate Change/Disease reason for extinction??

*Cenozoic Era*

Continents were drifting apart—present time of Earth

African plate collided with European plate creating the Alps

India slammed into Asian plate creating Himalayas

Climate was cooled causing several “ice ages”

*Mammals Survive because*

Small size easier to maintain body temperature in climate change

Ability to Hibernate during an extreme event

Mothers provide food for young from milk, No other organisms do this (mammals unique)

Cenozoic Era

Age of Mammals (65mya- present day) 2 Periods

Tertiary Period (65mya – 1.6mya)

Earth’s climate was warm and mild Ocean mammals like dolphins and whales

evolve Land-insects, flowering plants and

mammals, birds dominate Mega mammals mammals evolve Alps and Himalayas Form

Quaternary Period: (1.6 mya- today)

Mega mammals die out/ (Climate Change?) Present period Humans appear—100,000 years ago Grand Canyon forms Last ice age 15,000-10,000 years ago