Biology Exam II --> Geological History and Extinction

Cambrian is important b/c

it is when most animal phyla appeared

Extinction is

Natural

Fossilization occurs how?

under right conditions and with right organisms

ex.) organisms w/ hard exoskeleton

Asteroids

caused dino extinctions

Asteroid Theory was determined how

there was iridium in rock layer

iridium is found in asteroids, not earth

rock layer was around 65 myo, approximately when the dinos disappeared

crater for asteroid found in Gulf of Mexico

Inferences with isotopes

plants and animals incorporate isotopes at ratio they occur in atmosphere

C14 —> decays when organism dies

measuring remaining C14 allows age of fossil to be determined

Grasslands

earth dried out, grasslands expanded

shift from C3 —> C4 Grasses

C4 Grasses

harder for herbivores to chew

horse body size and teeth size increased to adapt

Vegetation Dynamics

specific bush only in deserts is indicator of desert conditions in the past

Pack rats

their urine and fecal matter can be analyzed to identify vegetation near cave it lived in for long time

Wegener & Plate Tectonics

continents are not static and constantly in motion at a very slow rate

Importance of Plate Tectonics

explains distribution of species in a planet

continents share rock assemblages and fossil. organisms

Where did energy come from to move the continents?

The crust floats on top of a molten core

Ocean crusts are ____ & ___ than continental crusts which are ____ and ____

Ocean crusts are heavier & younger than continental crusts which are lighter and older

Mid Atlantic Ridge

ridge running down middle of Atlantic

shows sea floor spreading

Magnetic Reversal

periodically, magnetic poles point towards north or south which happens every 800,000 yrs

Which ocean is getting biggger and which is getting smaller?

Atlantic is getting bigger and Pacific is getting smaller

Volcanoes occur at

junctions of plates

Divergent Plate Movement

plates are moving apart from each other

— can happen in continet

lake —> sea —> ocean

Convergent Plate Movement

plates move into each other

1. oceanic-oceanic

2. oceanic-continental

3. continental-continental

Oceanic-Oceanic

Subduction

one oceanic plate goes under

Oceanic-Continental

Oceanic plate goes down b/c continental plate is higher up

Continental-Continental

plates hit each other and create mountains

Panamanian isthmus

North American animal groups dispersed into South America and South American animal groups dispersed into North America

Camels

there are old world camels and south american camels

camels evolved in NA

it despersed from NA to old world and into SA via bering strait

Pleistocene Overkill

Ice Age

Humans hunting diverse mammal fauna leading to extinction of large mammal fauna

Humans arriving and large amount of animals disappeared

Tribites

Rise & fall showing Extinction is natural

Mass extinctions are not all due to

extraterrestrial events

Cretacious: not the biggest extinction only 35% went extinct (asteroid)

Permian: 95% went extinct

Permian Extinction Effects?

sea level drops

pangea forms

photosynthesis stopped —> O2 levels dropped and CO2 increased

massive glaciation

Anthropocene Era

1950s- Present

mass extinction event?

How are periods defined?

origination and extinction of biological species

leaves chemical signatures (ex. plastic, co2, methane, concrete)

Different atmosphere billions of yrs ago how?

no oxygen

3 process changing composition of atmosphere

volcanic activity: released water vapor, co2, and n2

chemical reactions: rain water combines with Co2 to make acid and dissolves rocks and makes soil

photosynthesis: byproduct is oxygen

Consequences of Oxygen

led to one of the greatest extinction events: great oxygen catastrophe

ozone layer

Great Oxygen Catastrophe

one of greatest extinction events

most organisms were anaerobic and either all went extinct or had to find somewhere without oxygen

Ozone layer benefits how

the great oxygen catastrophe created ozone layer as consequence

it is a UV shield and deflects high energy radiation

set up possibility for larger multicellular organisms