EVOLUTION! Gradual Change Over Time

The 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!!!! 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!!! 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

PALEONTOLOGY Paleontologists 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 Game Scientists 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 Rock Relative Age – dating by rock position.

Aging Fossils and Rock Absolute Dating - dating using isotopes

Let’s Take A Trip Through Time Geologic 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 Era Spanned 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… Cambrian Explosion! Lasted from about 544 to 245 million yrs ago Many 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 Era JURASSIC PARK!!…began about 245 million yrs ago Divided into Triassic, Jurassic, and Cretaceous periods Triassic: 1st mammals appear Jurassic: Dinosaurs rule! Cretaceous: Mammals spread out and flowering plants evolve…oak, fig, elm

Cenozoic Era- Hello Humans! Began approx. 66 million yrs ago Mammals start to flourish Primate species diversify during this time Modern human species evolving only 200,000 yrs ago!

THE ORIGIN OF LIFE Early 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 Ideas Francesco Redi ( ) Redi’s Experiment- used controlled experiment to disprove fly from meat theory.

Origin of Life Ideas Lazzaro Spallanzani (1729 – 1799) Used broth to disprove spontaneous generation

Spallanzani Experiment

Origin of Life Ideas Louis Pasteur (1822 – 1895) Also used broth, but changed Spallanzani’s experiment. Pasteur Seals It! BIOGENESIS!

Modern Ideas About Life Alexander Oparin ( ) 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 Theory

Necessities 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 Experiment

Evolution of Cells Prokaryotes were first true cells Anaerobic-lack of oxygen in atmosphere Competition led to autotrophs- produced own food supply Similar to archaebacteria- live in harsh conditions today! Finally, photosynthesis evolved supplying oxygen to atmosphere!