1. Fossil Evidence of Change Part 2 Chapter 14 Section 1

2. Dating Fossils Relative dating is a method used to determine the age of rocks by comparing them with those in other layers.

3. Law of superposition  states that younger layers of rock are deposited on top of older layers

4. Radiometric dating  uses the decay of radioactive isotopes to measure the age of a rock

5. This method requires that the half-life of the isotope, which is the amount of time it takes for half of the original isotope to decay, is known.

6. Uranium 238 decays to Lead 206 with a half-life of 4510 million years.

7. Geologic Time Scale (GTS) GTS is a record of Earth’s history Epochs are the smallest unit of geologic time lasting several million years

8. Periods are divisions of geologic time lasting tens of millions are years

9. Era is a unit of geologic time consisting of 2 or more periods that lasts hundreds of millions of years

11. Precambrian First 4 billion years Life 1 st appeared  cyanobacteria and eukaryotic cells also emerged

12. The Paleozoic Era In just a few million years, the ancestors of most major animal groups diversified in what scientists call the Cambrian explosion.

13. 1 st life on land emerged during this era Mass extinctions have occurred every 26-30 million years on average

14. Between 60-75% of the species alive went extinct in each of these events The cause of these extinctions include geological forces and increased volcanic activity  disrupting ecosystems and changing climate

15. The Mesozoic Era Mammals and dinosaurs fist appeared Flowering plants evolved from non-flower plants

16. Birds evolved from a group of predatory dinosaurs 65 million years ago, a meteorite struck Earth

17. Paleontologists have evidence of this due to the large amounts of iridium which is rare on Earth, but common on meteorites

18. The meteor probably did not wipe out all the species, but debris from the impact probably stayed in the atmosphere for months or even years affecting global climate

19. The Cenozoic Era Is the most recent era Mammals became the dominant land animals Humans appeared near the end in the Neogene period