Chapter 19: The History of Life
19–1
The Fossil Record
A. The Fossil Record
B. How Fossils Form
C. Dating Fossils
 Relative Dating
 Radioactive Dating
D. Geologic Time Scale
 Eras (Paleozoic, Mesozoic, Cenozoic)
 Periods
The Fossil Record
• Provides evidence
•
•
about history of life on
Earth
Shows how different
groups of organisms
change over time
More than 99% of all
species that have
ever lived on Earth
have become extinct.
Archaeopteryx
How Fossils Form
• How Fossils Form: Active Art
http://www.phschool.com/webcodes10/index.cfm?fuseaction=home.gotoWebCode&wcprefix=cbe&wcsuffix=5171
• Lucy’s fossil:
Water carries small rock
particles to lakes and seas.
http://www.pbs.org/wgbh/evolution/library/04/3/l_043_01.html
Dead organisms are buried
by layers of sediment, which
forms new rock.
The preserved remains
may later be discovered
and studied.
Dating Fossils
 Relative Dating
 Radioactive Dating
How old is this Archaeopteryx fossil?
150 million years old
Relative Dating
• estimate age of a fossil by
comparing to other fossils
• oldest fossils are usually in
deepest layers
• index fossils (trilobites)
used to compare the ages
of rocks and other fossils
• cannot determine exact
numerical age
Radioactive (“absolute”) Dating
• calculate numerical age of a
•
sample based on amount of
radioactive isotopes
Half-life = length of time required
for half of the radioactive atoms
to decay
• Carbon-14 half-life = 5770 yrs.
used to date younger fossils
• Potassium-40 half-life = 1.26 billion yrs.
used to date older fossils
•
http://www.pbs.org/wgbh/evolution/library/03/3/l_033_01.html
Relative vs. Radioactive Dating
Comparing Relative and Radioactive Dating of Fossils
Relative Dating
Can determine
Is performed by
Drawbacks
Radioactive Dating
Age of fossil with respect to
another rock or fossil (that is,
older or younger)
Age of a fossil in years
Comparing depth of a fossil’s
source stratum to the position
of a reference fossil or rock
Determining the relative
amounts of a radioactive
isotope and nonradioactive
isotope in a specimen
Imprecision and limitations of
age data
Difficulty of radioassay
laboratory methods
Geologic Time Scale
• represents evolutionary
time
• major changes in
animal/plant fossils at
specific rock layers
divided geologic time
according to major fossil
changes
Geologic Time Scale
Geologic Time Scale
First life = 4mya
19–2
Earth’s Early History
A. Formation of Earth
B. The First Organic Molecules (Miller & Urey)
C. How Did Life Begin?
 Formation of Microspheres
 Evolution of RNA and DNA
D. Free Oxygen
E. Origin of Eukaryotic Cells
F. Sexual Reproduction and Multicellularity
Formation of the Earth
• Earth formed about 4.6
•
billion years ago.
Early earth’s atmosphere
contained:
 Hydrogen cyanide, carbon
dioxide, carbon monoxide,
nitrogen, hydrogen sulfide, and
water vapor.
• Little or no oxygen
• Hot! No oceans or liquid
water, just water vapor in air.
Early earth
Approx. 4 billion years ago
Miller-Urey Experiment
• What were the first organic
molecules on earth?
Mixture of gases
simulating
atmospheres of
early Earth
Spark simulating
lightning storms
• (1950’s) Miller & Urey made amino
acids by passing sparks through a
mixture of hydrogen, methane,
ammonia, and water vapor.
• (1995) one of Miller’s experiments
produced cytosine & uracil (found in
RNA)
• experiments suggest how simple
compounds found could combine
to form organic compounds
needed for life
Condensation
chamber
Water
vapor
Cold water
cools
chamber,
causing
droplets to
form
Liquid containing
amino acids and
other organic
compounds
How Did Life Begin?
• Under certain conditions, large
organic molecules can
sometimes form tiny bubbles
called proteinoid microspheres.
• These are NOT cells, but have
some of the characteristics of
living things.
 Selectively permeable membrane
 Can store and release energy
Free Oxygen
• No oxygen in early Earth’s
•
•
atmosphere. (3.5 bya)
Ancient photosynthetic
organisms (cyanobacteria)
produced a rise in oxygen
in the Earth’s atmosphere
(2.2 bya)
Cyanobacteria produce
stromatolite formation in
the ocean
Endosymbiotic Theory
Chloroplast
Aerobic
bacteria
Ancient Prokaryotes
Nuclear
envelope
evolving
Plants and
plantlike protists
Photosynthetic
bacteria
Mitochondrion
Primitive Photosynthetic
Eukaryote
Animals, fungi, and
non-plantlike protists
Ancient Anaerobic
Prokaryote
Primitive Aerobic
Eukaryote
Eukaryotic cells arose from living communities
formed by prokaryotic organisms.
Endosymbiotic Theory Video The Evolution of Cells
Sexual Reproduction & Multicellularity
• Eukaryotic cells
began to reproduce
sexually, producing
more genetic
variation, leading to
evolution of
multicellular
Ancient jellyfish fossil
organisms.
multicellular organism
Evolution of Life Concept Map
Evolution of Evolution
Life ofConcept
Map
Life
Early Earth was hot; atmosphere contained poisonous gases.
Earth cooled and oceans condensed.
Simple organic molecules may have formed in the oceans..
Small sequences of RNA may have formed and replicated.
First prokaryotes may have formed when RNA or DNA was enclosed in microspheres.
Later prokaryotes were photosynthetic and produced oxygen.
An oxygenated atmosphere capped by the ozone layer protected Earth.
First eukaryotes may have been communities of prokaryotes.
Multicellular eukaryotes evolved.
Sexual reproduction increased genetic variability, hastening evolution.
Geologic Time Websites
1. Go to Biology Page Website.
2. Click on Unit 5 Evolution
3. Look under WebLinks column.
4. Explore the following websites:
1. Geologic Time
2. A Brief History of Life
19–4 Patterns of Evolution
Macroevolution: large scale evolutionary
patterns that occur over long periods of
time. The six types are:
1.
2.
3.
4.
5.
6.
Extinction
Adaptive Radiation
Convergent Evolution
Coevolution
Punctuated Equilibrium
Developmental Genes and Body Plans
Extinction
• More than 99% of all species
•
•
that have ever lived are now
extinct.
Mass extinctions lead to
bursts of evolution that
produce many new species.
Ex. the extinction of the
dinosaurs cleared the way
for the evolution of mammals
and birds.
•
http://www.pbs.org/wgbh/evolution/library/03/2/l_032_02.html
•
http://www.pbs.org/wgbh/evolution/extinction/inde
x.html
K-T event (65 mya)
70% of species died
in a mass extinction
Adaptive Radiation
• Example = Birds on the
Hawaiian islands
evolved from a
common ancestor over
millions of years.
• The birds that survived
were most adapted to
their environment.
Birds on Hawaiian Islands
Convergent Evolution
• Unrelated organisms resemble one another.
• Ex. all organisms above have wings, adapted for
flying, however they evolved from different ancestors.
Coevolution
• Two species evolve in response to changes in each other over
•
time.
Ex. hawk moth evolved and has long feeding tube to suck
nectar from orchid
Plants and pollinators co-evolve
Punctuated Equillibrium
• Long, stable periods interrupted by brief periods of more rapid
•
change.
Ex. peppered moths evolved rapidly after industrial revolution.
Developmental Genes & Body Plans
• All animals have master control genes that code for
•
the a basic body plan.
Mutations cause variations in those body plans.
• http://www.pbs.org/wgbh/evolution/library/03/4/l_034_04.html
Macroevolution Flowchart
Species
that are
Unrelated
form
Related
in
under
under
in
in
Interrelationshiops
Similar
environments
Intense
environmental
pressure
Small
populations
Different
environments
can undergo
can undergo
can undergo
can undergo
can undergo
Coevolution
Convergent
evolution
Extinction
Punctuated
equilibrium
Adaptive
radiation