1. Chapter 17 The History of Life
Fossil imprint

2. What is the difference between relative dating and absolute dating?

3. Relative vs. Absolute Dating
Comparing Relative and Absolute Dating of Fossils
Can determine
Is performed by
Drawbacks
Relative Dating
Absolute 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

4. Principle of Superposition
In an undisturbed sequence of sedimentary rocks, the oldest rocks are on the bottom with the most recent on top.

5. How fossils are formed
Water carries small rock particles to lakes and seas.
Dead organisms are buried by layers of sediment, which forms new rock.
The preserved remains may later be discovered and studied.

6. Geological Time Scale
After the Precambrian Time, the time scale is divided into eras, which are subdivided into periods.
Era
Period
Time
(millions of years ago)
Era
Period
Time
(millions of years ago)
Era
Period
Time
(millions of years ago)
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
290 – 245
360–290
410–360
440–410
505–440
544–505
Quaternary
Tertiary
Cretaceous
Jurassic
Triassic
1.8–present
65–1.8
145–65
208–145
245–208
Vendian
650–544

7. Geological Time Scale
The major eras are Paleozoic, Mesozoic, and Cenozoic.
Era
Period
Time
(millions of years ago)
Era
Period
Time
(millions of years ago)
Era
Period
Time
(millions of years ago)
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
290 – 245
360–290
410–360
440–410
505–440
544–505
Quaternary
Tertiary
Cretaceous
Jurassic
Triassic
1.8–present
65–1.8
145–65
208–145
245–208
Vendian
650–544

8. Geologic Time Scale
Each period hosts significant evolutionary changes to species diversity and extinction.
Era
Period
Time
(millions of years ago)
Era
Period
Time
(millions of years ago)
Era
Period
Time
(millions of years ago)
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
290 – 245
360–290
410–360
440–410
505–440
544–505
Quaternary
Tertiary
Cretaceous
Jurassic
Triassic
1.8–present
65–1.8
145–65
208–145
245–208
Vendian
650–544

9. Summary of major events (pg. 429-34)
Era
Period
Time
(millions of years ago)
Key Events
Cenozoic
Mesozoic
Paleozoic
Precambrian
Time
Quaternary
Tertiary
Cretaceous
Jurassic
Triassic
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
1.8–present
65–1.8
145–65
208–145
245–208
290–245
363–290
410–363
440–410
505–440
544–505
650–544
Glaciations; mammals increased; humans
Mammals diversified; grasses
Aquatic reptiles diversified; flowering plants; mass extinction
Dinosaurs diversified; birds
Dinosaurs; small mammals; cone-bearing plants
Reptiles diversified; seed plants; mass extinction
Reptiles; winged insects diversified; coal swamps
Fishes diversified; land vertebrates (primitive amphibians)
Land plants; land animals (arthropods)
Aquatic arthropods; mollusks; vertebrates (jawless fishes)
Marine invertebrates diversified; most animal phyla evolved
Anaerobic, then photosynthetic prokaryotes; eukaryotes, then multicellular life

10. Hypothesis of early Earth
Very hot surface from colliding meteorites
Very hot planet core from radioactive materials
Volcanoes spewing lava and gases that helped to form the early atmosphere

11. Hypothesis of early Earth
About 4.4 billion years ago, Earth might have cooled enough for the water in its atmosphere to condense.
This might have led to millions of years of rainstorms with lightning, enough rain to fill depressions that became Earth’s oceans.
The oldest rocks dated are 3.9 million years old.

12. Fossils: evidence of an organism that lived long ago that is preserved in Earth’s rocks
Paleontologists estimate that about 95% species are extinct from life’s origins.
Climate and ancient geography can be determined from fossils.
Types of Fossils
Fossils Types
Formation
A trace fossil is any indirect evidence
A trace fossil is any indirect evidence
Trace fossils
left by an animal and may include a
footprint, a trail, or a burrow.
When minerals in rocks fill a space
Casts
left by a decayed organism, they make
a replica, or cast, of the organism.
A mold forms when an organism is
A mold forms when an organism is
Molds
buried in sediment and then decays,
leaving an empty space.
Petrified/
Petrified-minerals sometimes penetrate
and replace the hard parts of an
Permineralized
organism. Permineralized-void spaces
fossils
in original organism infilled by
minerals.
Amber-
At times, an entire organism was
Preserved or
quickly trapped in ice or tree sap that
frozen fossils
hardened into amber.

13. What has been learned from fossils
several episodes of mass extinction that fall between time divisions
mass extinction: an event that occurs when many organisms disappear from the fossil record almost at once
The geologic time scale begins with the formation of Earth about 4.6 billion years ago.

14. Precambrian – 87% of history
Oldest fossils about 3.4 billion years old resembling cyanobacteria stromatolites.
Stromatolites still form today in Australia from mats of cyanobacteria.
The stromatolites are evidence of the existence of photosynthetic organisms on Earth during the Precambrian.
Only prokaryotic life found in fossil record

15. End of Precambrian – 543 MYA
multicellular eukaryotes, such as sponges and jelly-fishes, diversified and filled the oceans

16. Paleozoic and Cambrian Period
Paleozoic Era: more animals and plants
Early: fishes, aquatic vertebrates, ferns
Middle: amphibians
Late: reptiles and mass extinction
Cambrian Period: oceans teemed with many types of animals, including worms, sea stars, and unusual arthropods

17. Mesozoic - 248 MYA Triassic Period: mammals and dinosaurs
Jurassic Period: dinosaurs and birds
Cretaceous Period: more mammals, flowering plants, but mass extinction of dinosaurs 65 MYA

18. Continental drift
Earth’s continents have moved during Earth’s history and are still moving today at a rate of about six centimeters per year.
The theory for how the continents move is called plate tectonics.

19. Miller-Urey experiment showed one possible way for inorganic molecules to form organic molecules.
Mixture of gases simulating atmospheres of early Earth
Spark simulating lightning storms
Cold water cools chamber, causing droplets to form
Condensation chamber
Water vapor
Liquid containing amino acids and other organic compounds

20. How eukaryotic cells evolved
Lynn Margulis proposed the endosymbiotic theory.
Chloroplast
Plants and plantlike protists
Aerobic bacteria
Ancient Prokaryotes
Nuclear envelope evolving
Photosynthetic bacteria
Mitochondrion
Primitive Photosynthetic Eukaryote
Animals, fungi, and non-plantlike protists
Ancient Anaerobic Prokaryote
Primitive Aerobic Eukaryote

21. Endosymbiotic theory
Eukaryotic cells may have engulfed prokaryotic cells & by mutualism created the “first mitochondria.”

22. Autotrophic bacteria are Cyanobacteria with chlorophyll
So, Eukaryotic cells may have engulfed prokaryotic cyanobacteria & by mutualism created the “first chloroplast.”

23. Evoutionary wise these Relationships may allow host to live longer & reproduce more, thus over time creating more complex eukaryotic cells

25. Macroevolution
Large-scale evolutionary patterns and processes that occur over long periods of time.
Includes 6 topics:
Extinction
Adaptive radiation
Convergent evolution
Divergent evolution
Punctuated equilibrium
Changes in developmental genes

26. Patterns of evolution
Darwin believed that organisms evolved gradually.
Niles Eldredge and Stephen Jay Gould believed punctuated equilibrium is how organisms evolved, periods of rapid evolution followed by periods of stasis.

27. Adaptive Radiation
Single species or small groups of species evolved into diverse forms living in different ways.

28. Convergent Evolution
Adaptive radiation can produce unrelated organisms that look similar due to similar environments.

29. Coevolution The process by which two species evolve in
Example: “This butterfly acquires a cardiac glycoside from members of the genus Asclepias. Because of their milky sap, these are commonly referred to as milkweed plants. The plants produce this toxin as a defense against herbivory, but the Monarch has the ability to sequester the toxin in fatty tissues so that it makes the butterfly unpalatable while not poisoning the butterfly.”
The process by which
two species evolve in
response to changes in
each, other over time.
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