EVOLUTION!EVOLUTION!

Gradual Change Over Time

The Record of LifeThe Record of Life

Early Earth=Not So Life Friendly!!◦Formed about 4.6 BILLION years ago!◦Meteor collisions forced gases into

atmosphere.◦Earth too hot for life though!!◦About 3.9 billion yrs ago….BRING ON

THE RAIN!!!◦Eventually, first oceans are formed…

OCEANS=LIFE!!!!OCEANS=LIFE!!!!About 3.5 billion yrs ago…Life

first appears!What evidence do we have??

◦Look at the rocks!◦Oldest rocks about 3.9 billion yrs old.◦Hold clues to the earth’s past!

FOSSILS!!!FOSSILS!!!

A fossil is any evidence of an organism that lived long ago.

Classified according to how they form◦Casts◦Amber-preserved and frozen fossils◦Trace fossils◦Petrified fossils◦Imprints◦Molds

Types of Fossils

• Mold- an imprint of the organism or body part

• Cast – when a mold is filled with hard minerals and the minerals take on the shape of the organism

• Petrification – hard parts of the organism are replaced by minerals

• Amber – tree sap that traps and hardens the organism

PALEONTOLOGYPALEONTOLOGYPaleontologists work with fossils

to determine when and where organisms lived throughout Earth’s history.

Use condition, position and location of fossils to try and figure out topography and geography of past environments.

The Dating GameThe Dating GameScientists use a variety of

methods to date fossils:◦Relative Dating-fossils on the bottom

are older then the one above them!◦Radiometric (Absolute) Dating-use

radioactive isotopes as clocks Decays at steady rate-measure amount

of decay to determine age

Aging Fossils and RockAging Fossils and Rock

Relative Age – dating by rock position.

Aging Fossils and RockAging Fossils and Rock

Absolute Dating - dating using isotopes

Let’s Take A Trip Through Let’s Take A Trip Through TimeTimeGeologic Time Scale: Based on

different types of living organisms that have appeared during Earth’s history.

Divided into FOUR eras:◦Precambrian◦Paleozoic◦Mesozoic◦Cenozoic

The Precambrian EraThe Precambrian EraSpanned from 3.5 billion to 544

million yrs ago

Accounts for 87% of Earth’s history

Stromatolites from cyanobacteria as well as trilobites originated during this era

The Paleozoic Era… The Paleozoic Era… Cambrian Explosion!Cambrian Explosion!Lasted from about 544 to 245

million yrs agoMany more animals and plants

appear!Many invertebrates: Worms,

echinoderms and arthropods, oh my!

Fish also appeared in the seas and ferns appeared on land.

The Mesozoic EraThe Mesozoic Era

JURASSIC PARK!!…began about 245 million yrs ago

Divided into Triassic, Jurassic, and Cretaceous periods

Triassic: 1st mammals appearJurassic: Dinosaurs rule!Cretaceous: Mammals spread out

and flowering plants evolve…oak, fig, elm

Cenozoic Era- Hello Cenozoic Era- Hello Humans!Humans!Began approx. 66 million yrs agoMammals start to flourishPrimate species diversify during

this timeModern human species evolving

only 200,000 yrs ago!

THE ORIGIN OF LIFETHE ORIGIN OF LIFEEarly ideas for how life came to

be were much different than today.

Spontaneous Generation: process by which life was thought to be produced from nonliving matter.◦Ex.-flies from meat and mice from

old blankets in a barn!

Disproving these IdeasDisproving these Ideas

Francesco Redi (1626-1697)

Redi’s Experiment- used controlled experiment to disprove fly from meat theory.

Origin of Life IdeasOrigin of Life Ideas

Lazzaro Spallanzani (1729 – 1799)

Used broth to disprove spontaneous generation

Spallanzani ExperimentSpallanzani Experiment

Origin of Life IdeasOrigin of Life Ideas

Louis Pasteur (1822 – 1895)

Also used broth, but changed Spallanzani’s experiment.

Pasteur Seals It!BIOGENESIS!

Modern Ideas About LifeModern Ideas About LifeAlexander Oparin (1894 -1980)Said that the compounds in

the earth’s atmosphere during early earth times could have formed simple organic compounds such as amino acids

These organic compounds could have then formed macromolecules essential to life

The Oparin TheoryThe Oparin Theory

Necessities for LifeNecessities for Life

Simple organic molecules-Miller and Urey simulated early Earth conditions to show that molecules can be produced from such conditions

Complex organic compounds and cells- Protocells-large, ordered structure that carries out some life activities

Growth, division, metabolism

Miller & Urey ExperimentMiller & Urey Experiment

Evolution of CellsEvolution of Cells

Prokaryotes were first true cellsAnaerobic-lack of oxygen in

atmosphereCompetition led to autotrophs-

produced own food supplySimilar to archaebacteria- live in

harsh conditions today!Finally, photosynthesis evolved

supplying oxygen to atmosphere!