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

Comparison of the DinosaursTriassic Jurassic Cretaceous

small(Stegosaurus)Med- large

T-rex, Triceraptops, RaptorsLargest

Cold blooded Warm blooded Warm blooded

Reptile-like More Advanced Most Advanced/ Bird like in many ways

Simple body plans4 legs herbivores2 legs carnivores

Defenses against Preadtors

Most advanced featuresHollow bones (t rex, raptors)Proto-feathers on skin

Each continent had its own unique Dinosaurs

*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