Fossils
Biology 2
Thursday, January 31, 2013
Evolution
Change in the genetic composition of a
group of organisms over time.
Causes:
• Natural Selection
• Artificial Selection
• Genetic Engineering
• Genetic Drift
• Hybridization
• Mutation
Thursday, January 31, 2013
Speciation
development of two or more species from a
single species
Species
A
Species
B
Species
C
Ancestral Species
Thursday, January 31, 2013
Species
D
Speciation Activity 3
Thursday, January 31, 2013
Types of Speciation
Allopatric - geographical separation
Sympatric - occurs in same geographical
area (hybrids, polyploids)
Thursday, January 31, 2013
Isolating Mechanisms
Spatial
Temporal
Behavioral
Mechanical
Zygote Mortality
Hybrid Sterility
Hybrid Reduced Fitness
Thursday, January 31, 2013
Fossil
remains or traces
of ancient living
organisms
evidence for
evolution
show pattern of
evolution
can be dated
Thursday, January 31, 2013
Relative Dates
Principle of Superposition - younger
sedimentary rocks are on top of older
sedimentary rocks.
Principle of Cross-Cutting Relations: any
geologic feature is younger than anything
else it cuts across
Thursday, January 31, 2013
Activity - Relative Age
Shale/Siltstone
Shale/siltstone
Limestone
Sandstone
Basalt
Basalt
Limestone
Sandstone
Pegmatite
Slate
Slate
Pegmatite
Granite
Granite
Oldest
Thursday, January 31, 2013
Radiometric Dating
Isotopes - atoms of same element with
different atomic weights
e.g. U-235 and U-238
92 protons, 143 vs 146 neutrons
U-235 unstable
Thursday, January 31, 2013
U-235 ➔ Pb-207
Half-Life
Time for 1/2 the isotope atoms to decay
U-235 ➔ Pb-207
704 million years
100% U-235 ➔ 50% U-235, 50% Pb-237
Thursday, January 31, 2013
Uranium Decay
half life
time (millions)
% of U-235
0
0
100
1
704
50
2
1408
25
3
2112
12.5
4
2816
6.25
5
3520
3.125
6
4224
1.5625
Thursday, January 31, 2013
Graph of Uranium Decay
100
Percent uranium Remaining
90
80
70
60
50
40
30
20
10
0
0
1000
2000
3000
Million Years
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4000
5000
Log Graph of Uranium Decay
Percent uranium Remaining
100
10
1
0
1000
2000
3000
Million Years
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4000
5000
Graph of Uranium Decay
Percent uranium Remaining
100
10
0
500
1000
1500
Million Years
Thursday, January 31, 2013
2000
2500
How Old is Pegmatite?
U-235:Pb-207 1:1
Do others!
50% U-235 : 50% Pb-207
Percent uranium Remaining
100
700 million
10
0
Thursday, January 31, 2013
500
1000
1500
Million Years
2000
2500
Ages of Layers
Siltstone - 70
Basalt - 380
Granite - 1400
Percent uranium Remaining
Pegmatite - 700
100
10
0
500
1000
1500
Million Years
Thursday, January 31, 2013
2000
2500
Rock
Shale/Siltstone
Limestone
Sandstone
Basalt
Age
Shale/siltstone
70
Basalt
Limestone
Sandstone
Pegmatite
380
704
Slate
Slate
Pegmatite
Granite
Granite
Oldest
Why not date other layers?
Thursday, January 31, 2013
1408
Types of Rock
Igneous - formed by melting e.g. granite, basalt
Best for dating - melting “resets” clock (lead is lost)
Sedimentary - formed by weathering and deposition of
particles from parent rock, e.g. sandstone, limestone
Dating indicates age of parent rock, not rock layer itself
Metamorphic - from recrystallization or other rock due
to high temperature and pressure e.g. marble and
slate
Thursday, January 31, 2013
Dating Fossils
Shale/Siltstone
Limestone
Sandstone
Basalt
Rock
Age
Shale/siltstone
70
Basalt
Limestone
Sandstone
Pegmatite
380
704
Slate
Slate
Pegmatite
Granite
Granite
Oldest
Fossil bacteria and archaea are in slate 704-1408
Fossil trilobites in limestone
380-704
fossil cycads in shale and siltstone
70
Thursday, January 31, 2013
1408
Geological Eras
Precambrian (4600 - 600 mya)
Paleozoic (600 - 250 mya)
Mesozoic (250 - 65 mya)
Cambian Explosion
Permian Extinction
Cenozoic (65 mya - present) Cretaceous Extinction
Thursday, January 31, 2013
Precambrian: 4600-600 mya
4600 mya - earth forms
3500 mya - 1st prokaryotes fossils
2100 mya - 1st eukaryotes
1000 mya - 1st multicellular
Thursday, January 31, 2013
Early Earth
hot
atmosphere
mostly H2O, N2, CO2
trace H2, CH4, NH3
Oceans form as earth cools
Thursday, January 31, 2013
Miller’s
Experiment
1953
Spark
Early
Atmospheric
Gases
Small Organic Molecules
sugar, amino acids, fatty acids
Thursday, January 31, 2013
Evolution of 1st Cells
Monomers
amino acids
nucleotides
fatty acids
Thursday, January 31, 2013
Polymers
Protocell
Protein
RNA, DNA
lipids
lipids around
polymer
True Cell
(Replicate)
Stromatolites
(early fossils - blue-green bacteria)
http://en.wikipedia.org/wiki/
File:Stromatolites_in_Sharkbay.jpg
Thursday, January 31, 2013
Paleozoic Era - 600 - 225 mya
Cambrian Explosion
Invertebrate animals e.g. trilobites.
1st Vertebrates - fish, salamanders,
reptiles
Algae
Lichens - 1st land plant-like
1st Mosses
1st Ferns
1st Seed Plants
Permian extinction 95%
Thursday, January 31, 2013
Periods
Subdivisions of Eras
Permian (299-251)
Carboniferous (359-299)
Paleozoic
Era
Devonian (416-359)
Silurian (444-416)
Ordovician (488-444)
Cambrian (542-488)
Thursday, January 31, 2013
Mesozoic Era - 225 - 65 mya
Age of the Reptiles
Ferns common - some
tree size.
Seed ferns - extinct
intermediate between
non-seed and seed
plants.
1st Flowering plants
1st Birds and Mammals
Great Cretaceous
Extinction (76% species)
Thursday, January 31, 2013
Periods
Cretaceous 145-65
Jurassic 145-200
Triassic 200-251
Cenozoic Era - 65 mya - present
Insects and mammalsdominant land animals
Flowering plants dominant land plants.
Algae-dominate sea
Great Quaternary
Extinction?
Periods
Thursday, January 31, 2013
Quaternary (1.8-0)
Tertiary (65-1.8)