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:
Pangaea – central land massLaurasia [northern continents]
& Gondwana [southern continents]end of Mesozoic = modern continents
[Triassic]
Discuss
What is the difference betweenContinental Drift and Plate Tectonics?
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
Discuss
Name and describe 5 types of fossils.
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
Discuss
Discuss with a partner certain things that we can and can’t learn from
fossils.
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,
Discuss
What is the difference between relative dating and radiometric 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
Discuss
What are potential problems in relative dating and in radiometric dating?
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.
HomeworkComplete the Stego/Horse worksheet you
received.
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