Intro to EvolutionEvolution simply means change over time.

many things evolve, including languages, and your view of the world.

Intro to EvolutionThis unit is meant to introduce you to:

the development of current evolutionary theory and subtopics

processes which influence the change of species over time

This unit is not meant to:tell you what you have to believe

Intro to EvolutionThis unit is a spectacular view into what

science truly is:we are constantly learning new things on

our own and from othersmaking mistakes and learning from themmaking revisions based on new dataimproving on techniques that work or

don’t work at all.taking data and attempting to determine its

meaningfiguring out the “how” of things

Unit 5 – Lecture 1

Evolutionary TimelineThe evolutionary timeline is divided into

sections of time called eras – which are then divided into smaller units of time called periods.units of time are determined through use of

radiometric dating methods, fossil/rock identification, and geographic strata [rock layers].

evolutionists estimate the age of the earth to be approximately 4.5 billion years old

Evol. Timeline – cont’dHadean: 3.8-4.5 billion years ago

think “Hades” very hotvery little

free oxygen, lots of CO2

lots of N2 [nitrogen] gas

lots of water vapor

Evol. Timeline – cont’dPrecambrian [anything from hadean to

cambrian…]cyanobacteria

and other prokaryotes

sponges &cnidarians[jellyfish/anemone]

Evol. Timeline – cont’dPaleozoic [542 mya – 251 mya]

six periods – need to know: Cambrian [1st of six]sudden occurrence - “explosion”

of life [Cambrian Explosion] seen in fossil recordworms, sea stars, trilobites,

fish, reptiles…other chordates and

hard-bodied organisms

Evol. Timeline – cont’dMesozoic [251 mya – 65 mya]

three periods :Triassic – small mammalsJurassic – dinosaurs Cretaceous – flowering plants

Evol. Timeline – cont’dCenozoic: 65.5 million years ago - present

lots of mammals

Continental DriftContinental Drift Theory states that

continents have moved throughout historycontinents are still moving approx 6cm a

year

Plate Techtonics explains HOW continents move

Continental Drift – cont’dContinental Movement:

Pangea – central land massLaurasia [northern continents]

& Gondwana [southern continents]end of Mesozoic = modern continents

[Triassic]

FossilsFossil – evidence of an organism which lived

long agopaleontologist – scientist who studies

ancient lifemost fossils are found in sedimentary

rock

Fossils – cont’dTypes of Fossils:

trace fossils – animal markings [footprint, trail, burrow]

Fossils – cont’dTypes of Fossils:

casts– mineralization of a space left by a decayed organism [most fossils you think of]

molds– empty space in rock from a decayed org.

Fossils – cont’dTypes of Fossils:

imprints – made typically by thin objects that have been pressed into an area

Fossils – cont’dTypes of Fossils:

carbonized – high temps & pressures expel gaseous elements leaving only carbon

Fossils – cont’dTypes of Fossils:

petrified – entire organism is replaced by mineral matter.

Fossils – cont’dTypes of Fossils:

ice- or amber- preserved fossils [True-Form Fossils]

Fossils – cont’dTypes of Fossils:

permineralization – pores are filled with mineral matter without getting rid of organic [carbon] material

Fossils – cont’dTypes of Fossils:

coprolite – fossilized dino poop

Fossils – cont’dWhat do we know about

this fossilized organism?

Fossils – cont’dFossils CAN Tell Us…[sometimes]

what an organism looked likewhat kinds of food it probably ate

exceptions…like the panda – has very sharp teeth for eating rough bamboo

what type of area it may have lived in / climate

geography of the area it lived in

Fossils – cont’dFossils CAN’T Tell Us…

what colors an organism wasalmost anything about behavior

science does attempt some basic conclusions about organisms based on how they are foundnests [nurturing], found traditionally in large groups [may have been a pack organism], etc.

what it sounded like we can make comparisons and guess at times

based on structure similarities

Dating MethodsRelative Dating – dating

new samples based off of comparison to previously dated materialsuses circular reasoning:

dating rocks by their fossils

dating fossils by the rock in which they are found

Dating Methods – cont’dRelative Dating [cont’d]

geologic layers as in the record are not actually found in their stated order anywhere on earth; they are approximated based on comparison of fossils and other rock

these things can lead to misinterpretation

Dating Methods – cont’dRadiometric Dating – examining the chemical

“half-life” of a substance in the sample to determine its approximate age

Dating Methods – cont’dRadiometric Dating [cont’d]

half-life – the amount of time it takes for half of a substance to change [decay] into another substance

based on isotopesisotope – atoms of an element with a

different number of neutrons than is typicalthe measured isotopes are radioactive and

slowly become non-reactive [this is what is measured]

Dating Methods – cont’dRadiometric Dating [cont’d]

ex: Carbon-14 dating, Potassium-Argon dating,

Dating Methods – cont’dProblems with Radiometric Dating

must know original amount of substance present to calculate time

must assume constant decaymust know no outside influence occurred

[like water, extra heat or pressure, other substances which react]

Dating Methods – cont’dProblems with Radiometric Dating

can’t date rocks which have been in water, but many fossils are formed in sedimentary rockin this case, rock ages are dated by the

fossils found in them that have been previously identified

recent samples showing millions of yearsMt. St. Helens – dated 10 yrs after eruption;

showed almost 3 million years datesamples showing negative age

Science!There are ways that ALL techniques can be

refined and improved – that’s the job of science – to keep learning more and going farther with research and doing many trials [when possible] to get to the most accurate data possible.

To Know.