1. History of Life on Earth Websites to explore: http://www.pbs.org/wgbh/nova/evolution/brief-history-life.html http://science.nationalgeographic.com/science/prehistoric-world/prehistoric-time-line/ http://www.ucmp.berkeley.edu/help/timeform.html

2. Oxygen starts to accumulate due to photosynthetic bacteria (2.4 bya) Eukaryotic Cells first evolve due to endosymbiosis (1.9 bya) Sexual Reproduction Begins (1 bya) Prokaryotic Cells first evolve (3.5 bya) Multicellularity (1.7 bya)

3. Endosymbiosis is the theory that primitive eukaryotic cells engulfed prokaryotes but didn’t digest them Heterotrophic prokaryote  mitochondria Photosynthetic prokaryote  chloroplast Both have double membranes

4. Fossils

5. Paleontology is the scientific study of the fossilized remains of early life on Earth. The remains can be from any type of life. Paleontology Animals Plants Bacteria Fungus fungus spore sac plant fossil ammonite cyanobacteria

6. What is a Fossil? A fossil is any remains or trace of life that has been preserved at some time in the past. To be considered a fossil, it must be at least ten thousand years old. The two main categories of fossils are I. Body fossils II. Trace fossils (coprolite)

7. Body Fossils are the actual body or body parts of an organism that have been preserved. They can be preserved in many ways. I. Body Fossils gastropod A1. Original skeletal material This means that the hard parts of the organism are preserved as the original material. Megaladon tooth

8. A2. Original Body Material in Tar Tar pits are excellent areas to preserve life as a fossil. Why? No oxygen. The La Brea tar pit in California is one of the most famous areas. saber-toothed cat skull

9. A3. Original Body Material in Amber Some trees make a sticky and thick liquid called resin. Small animals such as insects and spiders can get trapped and become preserved.

10. A4. Original Body Material in Ice Animals can get trapped in cracks of ice sheets or in water that becomes ice. Mammoth have been found frozen in ice. (This specimen died in ice 39,000 years ago)

11. B1. Remnant-Petrified Fossils An organism is buried before it can decompose, and dissolved minerals underground can slowly replace the hard parts of buried organisms with minerals. Is almost exact copy of the original organism, including internal structures. (Ex: Looks like tree cells!)

12. B2. Remnant-Cast (or replica) A cast is the same shape as the original organism. Casts are formed when the original parts are all dissolved away and the empty space is filled with sediment or minerals. Is the entire 3D shape of the organism, but no inner details. snail cast ammonite cast trilobite cast

13. cockroach leaf B3. Remnant-Imprint fossil A mark made in soft sediment that hardened- not total 3D shape of organism, just the texture of one side. fern

14. B4. Remnant- Mold A mold is the impression that an organism makes in the sediment as it was fossilized and then wore away. Is most of the 3D shape of the organism.

15. Relationship between molds and casts: mold is negative space whereas cast is positive space

16. How is a cast or mold fossil made? Only a small portion of organisms get fossilized. This is because they must be preserved under special conditions. Conditions favoring preservation: Rapid burial Stays buried Possession of hard parts Dies peacefully Avoids oxygen

17. A. Burrows These trace fossils show how an animal such as a worm moved through the soft sediment. worm tube II. Trace Fossils Trace Fossils are not the actual body, body parts, or remnants of an organism that have been preserved. These fossils show evidence of how an organism lived, how it moved, what its feet looked like, or what it ate.

18. B. Tracks Show how an animal moved and what its footprint looked like. These tracks can tell us a lot about the animal that made them. trilobite tracks Dinosaur tracks

19. C. Coprolite This is fossilized dung (poop). Coprolites can help show what and how an animal ate.

20. A. Relative dating Placing rocks and events in sequence Law of superposition – oldest rocks are on the bottom III. Dating of Fossils

21. B. Radiometric Dating What is Radioactivity? Radioactivity occurs when certain elements literally fall apart. Usually due to protons and neutrons or electrons being emitted by the nucleus of an unstable atom.

22. Radioactive Decay Radioactive elements “decay.” Decay occurs as an element changes to another element, e.g. uranium to lead. The parent element is radioactive, the daughter element is stable. Common Radioactive Elements Parents Element Daughter Element Half Life Carbon-14, C14 Nitrogen-14, N14 5,730 years Uranium-235, U235 Lead-207, Pb207 704 MY Potassium-40, K40 Argon-40, Ar40 1.3 BY Uranium-238, U238 Lead-206, Pb206 4.5 BY Rubidium-87, Rb87 Strontium-87, Sr87 48.8 BY

23. Radioactive Decay As the parent element decays, its amount decreases while the amount of the daughter element increases. Thus the ratio of parent : daughter elements changes over time. The decay rate is constant. Half-Life: the amount of time for half the atoms of a radioactive element to decay.

24. Mass spectrometer to measure ratio of parent and daughter elements. Radiometric Dating of Rock Samples Only two measurements are needed: 1. The parent:daughter ratio measured with a mass spectrometer. 2. The rate of decay.