Intro to Evolution
 Evolution simply means change over time.
 many things evolve, including languages,
and your view of the world.
Intro to Evolution
 This 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 Evolution
 This unit is a spectacular view into what
science truly is:
 we are constantly learning new things on our own
and from others
 making mistakes and learning from them
 making revisions based on new data
 improving on techniques that work or
don’t work at all.
 taking data and attempting to determine its
 figuring out the “how” of things
Unit 5 – Lecture 1
Evolutionary Timeline
 The 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’d
 Hadean: 3.8-4.5 billion years ago
 think “Hades”
 very hot
 very little
free oxygen,
 lots of CO2
 lots of N2
[nitrogen] gas
 lots of water vapor
Evol. Timeline – cont’d
 Precambrian [anything from hadean to cambrian…]
 cyanobacteria
and other
 sponges &
Evol. Timeline – cont’d
 Paleozoic [542 mya – 251 mya]
 six periods – need to know: Cambrian [1st of six]
sudden occurrence - “explosion”
of life [Cambrian Explosion]
seen in fossil record
 worms, sea stars, trilobites,
fish, reptiles…
 other chordates and
hard-bodied organisms
Evol. Timeline – cont’d
 Mesozoic [251 mya – 65 mya]
 three periods :
Triassic – small mammals
Jurassic – dinosaurs
Cretaceous – flowering plants
Evol. Timeline – cont’d
 Cenozoic: 65.5 million years ago - present
 lots of mammals
Continental Drift
 Continental Drift Theory states that continents have
moved throughout history
 continents are still moving approx 6cm a year
 Plate Techtonics explains HOW continents move
Continental Drift – cont’d
 Continental Movement:
 Pangaea – central land mass
 Laurasia [northern continents]
& Gondwana [southern continents]
 end of Mesozoic = modern continents
 What is the difference between
Continental Drift and Plate Tectonics?
 Fossil – evidence of an organism which lived long ago
 paleontologist – scientist who studies ancient life
 most fossils are found in sedimentary rock
Fossils – cont’d
 Types of Fossils:
 trace fossils – animal markings
[footprint, trail, burrow]
Fossils – cont’d
 Types 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’d
 Types of Fossils:
 imprints – made typically by thin objects that have
been pressed into an area
Fossils – cont’d
 Types of Fossils:
 carbonized – high temps &
pressures expel gaseous
elements leaving only
Fossils – cont’d
 Types of Fossils:
 petrified – entire organism is replaced by mineral
Fossils – cont’d
 Types of Fossils:
 ice- or amber- preserved fossils [True-Form Fossils]
Fossils – cont’d
 Types of Fossils:
 permineralization – pores are filled with mineral
matter without getting rid of organic [carbon]
Fossils – cont’d
 Types of Fossils:
 coprolite – fossilized dino poop
 Name and describe 5 types of fossils.
Fossils – cont’d
 What do we know about
this fossilized organism?
Fossils – cont’d
 Fossils CAN Tell Us…[sometimes]
 what an organism looked like
 what 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’d
 Fossils CAN’T Tell Us…
 what colors an organism was
 almost anything about behavior
science does attempt some basic conclusions
about organisms based on how they are found
 nests [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 with a partner certain
things that we can and can’t learn from fossils.
Dating Methods
 Relative Dating – dating
new samples based off of
comparison to previously
dated materials
 uses circular reasoning:
 dating rocks by
their fossils
 dating fossils by
the rock in which
they are found
Dating Methods – cont’d
 Relative 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
Dating Methods – cont’d
 Radiometric Dating – examining the chemical “half-
life” of a substance in the sample to determine its
approximate age
Dating Methods – cont’d
 Radiometric Dating [cont’d]
 half-life – the amount of time it takes for half of a
substance to change [decay] into another substance
 based on isotopes
 isotope – atoms of an element with a different
number of neutrons than is typical
 the measured isotopes are radioactive and slowly
become non-reactive [this is what is measured]
Dating Methods – cont’d
 Radiometric Dating [cont’d]
 ex: Carbon-14 dating, Potassium-Argon dating,
 What is the difference between
relative dating and radiometric dating?
Dating Methods – cont’d
 Problems with Radiometric Dating
 must know original amount of substance present to
calculate time
 must assume constant decay
 must know no outside influence occurred [like
water, extra heat or pressure, other substances
which react]
Dating Methods – cont’d
 Problems with Radiometric Dating
 can’t date rocks which have been in water, but many
fossils are formed in sedimentary rock
 in this case, rock ages are dated by the fossils
found in them that have been previously
 recent samples showing millions of years
 Mt. St. Helens – dated 10 yrs after eruption;
showed almost 3 million years date
 samples showing negative age
 What are potential problems in
relative dating and in radiometric dating?
 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
 To Know.
 Complete the Stego/Horse worksheet you received.

Timeline, Fossils & Dating Methods