1. Fossils

2. What is a fossil? preserved remains of a living thing
Paleontologist
preserved remains of a living thing
scientist who studies fossils

3. How do fossils form? Fossil Formation living things die
buried by sediment
sediment hardens
preserved in rock
Fossil Formation

4. Types of Fossils
a mark or cavity made in a sedimentary surface by a shell or other body.
copied shape of organism
fills in empty space of mold
Mold
Cast

5. Types of Fossils Petrified Fossil Trace Fossil
minerals replace organism
“turned to stone”
evidence of ancient organisms
ex. footprints

6. Organisms preserved in:
Tar
Amber (hardened sap)
Ice
Preserved Remains

7. Fossil Record shows how organisms have changed over time
supports the theory of evolution
Fossil Record

8. Fossils provide a past environments
picture for: past climates
changes in Earth’s surface

9. Finding Relative Age

10. Relative Age
Absolute Age
-age compared to age of other rocks
-number of years since the rock formed
-calculated by radioactive decay

11. Law of Superposition
-used to determine relative age of rock
- layering of sediment
-the oldest layer is at the bottom youngest layer at the top in undisturbed sequences.

12. Geologic Column
Disturbing Forces
An ideal sequence of rock layers.
Makes it easier to identify difficult ones.
Some layers are disturbed by forces within the Earth, which causes some layers to not be horizontal.

13. Disturbed Forces Unconformity
Disturbing events are always younger than rock layer they disturb.
Faults, intrusions, folding, tilting.
-gap in geologic record. Missing part of geo column.
Non-deposition or erosion.

15. Using Fossils to Date Rocks
-geologists give a relative age to a layer
-also give same age to matching layers at other locations
-help geologists match rock layers
1. widely distributed
2.organism that existed
briefly
-tell relative age of layers in which they occur
Using Fossils to Date Rocks
Index Fossil

16. Radioactive Dating

17. Absolute Dating Radioactive Decay
To determine absolute age: the # of years existed.
Analyze unstable isotopes of radioactive elements.
Isotope: atoms of the same element that have the same number of protons but difference numbers of neutrons.
-elements break down and release particles and energy at a steady rate.

18. -time it takes for half of a radioactive atom to decay
Rate of Decay
Half-life
-rate is constant (never changes)
-called half-life
-time it takes for half of a radioactive atom to decay

19. Types of Radiometric Dating
determine absolute age
1. determine amount of
radioactive element
in rock
2. compare with
amount of stable
element in rock

20. Potassium- Argon Dating
Uranium-Lead Dating
-potassium 40 decays to stable argon
Potassium-40 has a half-life of 1.3 billion years.
Uranium 238 decays to lead- 206
Half-life of uranium-238 is 4.5 billion years

21. Rubidium- Strontium Dating
Carbon-14 Dating
Rubidium-87 decays to Strontium-87.
Half-life of rubidium- 87 is 49 billion years.
Carbon-12 and Carbon-13 are stable isotopes and Carbon- 14 is radioactive.
When animal decays, carbon-14 has half-life of 5,730 years.
Dates more recent things (mammoths, fossils, etc.)

22. How old is Earth? -Scientists think Earth is even older
-oldest rocks found - 4 billion years old
-Scientists think Earth is even older

23. The Geologic Time Scale

24. Geologic Time Scale
-record of life forms and events in Earth’s history
-changes in life forms mark where one unit of time ends & the next begins

25. Divisions of Time Eras -scale begins with Precambrian Time
-divided into
eras
periods
epochs
-long units of time
-three eras:
Paleozoic
Mesozoic
Cenozoic

26. Periods Epochs -divisions of eras -10,000,000 to 2,000,000 years
-ex. Jurassic
Cretaceous
-divisions of Cenozoic period
-more events took place; more fossils to sort

28. Earth’s History

29. Precambrian Time -Earth formed from dust and gas 4.6 billion years ago
-pulled together by gravity
-interior became hot & molten
-after millions of years, lava flowed over surface
-lava built the 1st continents
-earliest life similar to today’s bacteria (formed 3.5 billion y.a)
-photosynthesis began 2.5 b.y.a
-organisms had soft bodies, left few fossils
-jellyfish

30. Paleozoic Era Vertebrate -many new organisms evolved
-many had hard shells/skeletons C
-all animals lived in sea C
-jawless fish evolved: *1st vertebrates O
-animal with a backbone
-plants began to grow on land S
-first insects also appeared
-many fish lived in seas
-animals also began to go on land D
-lungfish: 1st vertebrates on land
-evolved into amphibians C

31. Amphibians Reptile Mass Extinction
-lives part of life on land, part in water
-reptiles started to evolve
-scaly skin, lays eggs
-end of Paleozoic era, many organisms died out
-many types of living things became extinct at same time
-cause unknown
-one theory: climate change
-killed 95% of ocean life
-fish and reptiles survived

32. Pangaea
-supercontinent formed 260 million years ago
-caused major climate changes
-many organisms died
-after formed, broke apart again

33. Mesozoic Era

34. Mesozoic Era Triassic Mammal
-three periods: Triassic, Jurassic, Cretaceous
-“Age of Reptiles”
-225 million y.a., 1st dinosaur appeared (Coelophysis)
-mammals also appeared
-warm-blooded vertebrate that feeds its young milk
-evolved from warm-blooded reptiles
Mesozoic Era
Triassic
Mammal

35. Jurassic -dinosaurs dominant on land -plant eaters and meat eaters
-“ruled” Earth for 150 mill. years
-one of first birds appeared
*Archaeopteryx “ancient winged thing”
-paleontologists think birds evolved from dinosaurs

36. Cretaceous -reptiles still dominant
-meat eaters, like T- rex, ruled the land
-mammals still evolving
-flying reptiles became extinct
-flowering plants evolved
-at the end, another mass extinction occurred

37. Theories of what caused the mass extinction
-One theory: an asteroid struck the Earth
-threw huge amounts of dust and vapor into the air
-many organisms died instantly
-blocked sunlight for years
-many died from starvation
-no dinosaurs survived
-Another theory: volcanic activity caused major climate change
Theories of what caused the mass extinction

38. Cenozoic Era Tertiary -Age of Mammals
-mammals evolved adaptations to live in many different environments
-climate warm and mild
-whales & dolphins appeared
-grasses evolved; providing food

39. Quaternary -climate cooled causing Ice Age
-much of Earth’s waters froze
-climate began to warm 20,000 years ago; melted glaciers
-ocean life flourished
-flowering plants and mammals became common (bats, cats, dogs, cattle, humans)
-human ancestors appeared 3.5 million years ago
-modern humans evolved 100,000 years ago

40. Evolution and Natural Selection
Chapter 7

41. Species
- A group of organisms
- Can mate and reproduce
Adaptation
- A characteristic
- Helps an organism survive and reproduce
Evolution
- A process
- Gradual change over time
Extinct
organism no longer exists
organism did not adapt or evolve

42. Ways to Compare Organisms
1. Compare skeletons
2. Compare DNA

43. - Studied evolution on Galapagos Islands
Charles Darwin
- studied fitches (birds)
- Some organisms are more adapted
Natural Selection
- They have higher chance of surviving
- Will produce more offspring