The History of Life: Fossil Record & Evolutionary Patterns

1. The History of Life Chapter 19

2. The Fossil record • Palentologists study fossils • These records provided evidence about the history of life on earth • It shows that different organisms have changed over time • Some even became extinct

3. Interpreting Fossil Evidence • Relative dating- used to determine the age of a fossil • You compare the fossil’s placement in the rock layer with other fossils in the rock • The rock layers are formed by age with the oldest on the bottom

4. Index fossil • Can be used if the species is easily recognized and existed for a short period but have a wide geographic range

5. Radioactive dating • Scientists calculate the age of a sample based ion the amount of remaining radioactive isotopes it contains • The half life is the minimum amount of time it takes for half of a radioactive element to decay

6. Geological time scale • Used to divide time • After precambrian time, the basic divisions of the geological time scale are eras, periods, and epochs

7. eras • Paleozoic era- 544 million years ago, vert and invert • Mesozoic- 251 million yrs ago, dino and mammals • Cenozoic- 65 million yr ago, mammal age

8. Periods and epochs • Period range in length from 10 million years to less than 2 million years • Further divide periods into epochs

9. Earths Early History • Formation of the earth occurred 8.2 billion years ago • Its early atmosphere contained hydrogen cyanide, carbon dioxide, carbon monoxide, nitrogen, hydrogen sulfide, and water

10. First organic molecules • Miller and Urey did an experiment which suggested how mixture of compounds could have arisen from simplier compounds present on primitive earth

11. How Did Life begin? • 1. formation of microspheres • 2. evolution of RNA and DNA • 3. free oxygen in air drove some life forms to extinction and evolved others

12. Origin of Eukaryotic Cells • The endosymbiotic theory proposes that eukaryotic cells arose from living communities formed by several organisms • After eukaryotic cells arose, those cells began to reproduce sexually • This enabled evolution to take place at a greater rate

13. Evolution of multicellualr life forms • 90% of Earth’s history occurred during Precambrian • Simple anaerobic forms appeared and were followed by photosyntheitc forms which added oxygen to the air • Aerobic forms evolved and eukaryotes appeared • Early in Paleozoic era the fossil record became rich with evidence of many types of marine life • Life was highly diverse by the first part of Paleozoic era

14. Cambrian Period • This is when diversification of life occurred • Organisms had hard part and first animilia phyla evolved • Trilobites were common

15. Ordovician and silurian periods • Octopus and squid ancestors appeared along with aquatic arthropods

16. Devonian period • Animals began to invade the land • Fish developed the ability to crawl on leglike fins • Fish had jaws, bony skeletons, and scales

17. Carboniferous and permian period • Life expanded over the earth’s continents • Other groups of vert evolved from amphibians • Mass extinction occurred at the end of the Paleozoic era • It affects both plants and animals on land and on sea • 95% of the complex life in the ocean disappeared

18. Mesozoic era • Increase dominance of the dinosaurs • 1. triassic period-fish, reptiles insects • 2. jurassic period-dinosaurs dominant • 3. cretaceous period-reptiles still dominated, but another mass extinction occurred

19. Cenozoic era • Mammals evolved adaptations that allowed them to live in various environments

20. Patterns of evolution • Macroevolution- large scale change that take place over a long time • There are 6 important patterns to macroevolution: • 1. mass extinction • 2. adaptive radiation • 3. convergent evolution • 4. coevolution • 5. punctuated equilibrium • 6. changes in developmental genes

21. Mass extinction • Causes food webs to collapse

22. Adaptive radiation • Unrelated organisms come to resemble one another

23. coevolution • The process by which 2 species evolve in response to changes in each other over time • Ex flowering plants

24. Punctuated equilibrium • Patterns of long stable periods interrupted by brief periods of more rapid change