1. The History of Life (Chapter 17) Please set up your notebook for Cornell Notes

2. Fossils The scientists that study fossils are called paleontologists Fossils are remain of organisms that lived long ago The fossil record is all collected information about past life Provides evidence about the history of life on earth Shows how organisms have changed over time Fossil Record Fossils occur in a particular order More than 99% of all species that have existed are extinct

3. Interpreting Fossil data Relative dating  The age of a fossil is determined by comparing its placement with that of fossils in other layers Law of superposition  in an undisturbed series of rock layers, the oldest rocks are at the bottom Paleontologists use index fossils to compare relative ages of fossils Index fossil  a species that is easily recognized, existed for a short period of time and had a wide geographic range

4. Radioactive dating  using the known half-life of radioactive isotopes to determine the actual age of a fossil A half-life is the amount of time it takes for 1/2 of a sample of radioactive isotopes to decay

5. Geologic time scale  represents evolutionary time Eras  largest unit of geologic time 4 eras Precambrian  4.5 bya – 544 mya Paleozoic  544 mya – 245 mya Mesozoic  245 mya – 65 mya Cenozoic – 65 mya – present Periods  divide eras into sections

6. Patterns of evolution Macroevolution  large scale evolutionary patterns Extinction  organisms that are no longer living There have been several mass extinctions in Earth’s History When a lot of species die off, it allows surviving species to take over that niche Adaptive radiation  the process where one species evolves into several forms that live in different ways Darwin’s Finches Convergent Evolution  distantly related organisms evolve to resemble each other due to similar environmental pressures Whale and shark Bat and bird

7. Coevolution  two species evolve in response to change in each other over time Flowers and insects Punctuated Equilibrium  there are long periods of time with no change, with brief periods of rapid change Developmental Genes and Body Plans  changes in genes during embryo development can change adult form