1. Ch 14.1 The record of life You will … 1. examine how rocks and fossils provide evidence of changes in Earth’s organisms 2. correlate the geographic time scale with biological events 3. Sequence the steps by which small molecules may have produced living cells.

2. Early History of Earth A. No life could possibly exist: 1. Temperature: colliding meteorites; decay of radioactive materials, compression of minerals, volcanic eruptions. 2. Early Atmosphere: Small amounts of O 2, CO 2, and nitrogen. 3. Oceans: Approx. 4 billion years ago the Earth began to cool. Water in the atmosphere condensed causing rainstorms and lightening to occur for a few million years. Oceans formed and introduced the first organisms.

3. History in Rocks a. No direct evidence: Theories, physical process of reforming rocks. b. Fossils: We study fossils to make predictions. 99% of species are extinct. (Look at fig 14.1 Types of fossils) * c. Paleontologist: Scientist who study ancient life. Fossil bones and teeth can help determine size, movement, and type of organism. Climate and geography can also be determined. d. Fossil are found where? Sedimentary rock, bottoms of lakes, streams, and oceans.

4. The Age of a Fossil Layers of sedimentary rock can help determine age. a. Relative dating: Law of Super Position. The layers at the surface must be younger that the layers below it. Scientist can discover the order of appearance and extinction. b. Radiometric dating: Radioactive isotopes in rocks help determine exact age because unstable nuclei break down over time. The decay rate is called the half-life. c. Chemical Analysis helps Scientist: (Potassium-40, Carbon-14) More sampling and different methods help with consistency in results

5. A trip Through Geological Time: The calendar of Earth. a. The Geological Time Scale: Divided into 4 era (Precambrian, Paleozoic, Mesozoic, Cenozoic) Each era is subdivided into periods. Fig 14.4 b. Precambrian: Oldest fossils found in the deserts of Australia. Resembles modern species of bacteria called cyanobacteria. Accounts for 87% of Earth’s history. Prokaryotes only forms of life until the end of period when eukaryotic organisms emerged. (544 million years ago)

6. c.Paleozoic: Ended 245 million years ago. Cambrian period first showed an enormous increase in life. Oceans became filled with animals such as worms, sea stars, anthropods, fishes …. Then came amphibians, reptiles. A mass extinction occurred at the end of the period. ( 90% ocean and 70% land). d. Mesozoic: Began 245 million years ago. Drastic changes in organisms and geology. Divided into 3 periods: Triassic period: oldest, small mammals like mice were found. Jurassic period: (middle) became known as the age of the dinosaur. Cretaceous period: (last) marked the end of the dinosaur approx. 66 million years ago. Theories include a meteorite hitting the earth to cause extinction.

7. e.Changes during the Mesozoic period: Geological events changed the way species lived. The theory of the continental drift, plate tectonics, changed the way organisms lived. f.Cenozoic: 66 million years ago. We lived here now. Mammals flourish, primates appeared 30 million years ago. Humans 200,000 years ago