Daily Objective Become familiar with the Geologic Time Scale by assessing eras and periods of when biological events occurred.

14.1 Fossil Evidence of Change Objectives Describe a typical sequence of events of fossilization Compare techniques for dating fossils Identify and describe major events using the geologic time scale.

14.1 Fossil Evidence of Change Land Environments The History of Life Chapter 14  Earth formed about 4.6 billion years ago.  Gravity pulled the densest elements to the center of the planet.  After about 500 million years, a solid crust formed on the surface.

14.1 Fossil Evidence of Change Atmosphere The History of Life  The gases that likely made up the atmosphere are those that were expelled by volcanoes.  Unlike our present day atmosphere there was little or no free oxygen. Chapter 14

Clues in the Rocks The History of Life  A fossil is any preserved evidence of an organism.  Plants, animals, and bacteria can form fossils.  Approx. 99% of the species that have ever lived are now extinct but only a tiny % of those organisms are preserved as fossils. Most organisms decompose before they have a chance to become fossilized Fossil Evidence of Change Chapter 14

The History of Life 14.1 Fossil Evidence of Change Chapter 14

Fossil Formation The History of Life  Nearly all fossils are formed in sedimentary rock.  The sediments build up until they cover the organism’s remains.  Minerals replace the organic matter or fill the empty pore spaces of the organism Fossil Evidence of Change Chapter 14

Dating fossils The History of Life  Relative dating is a method used to determine the age of rocks by comparing them with those in other layers.  Relative dating is based on the law of superposition which states that younger layers of rock are deposited on top of older layers. i.e. stack of newspapers 14.1 Fossil Evidence of Change Chapter 14

 Uses the decay of radioactive isotopes to measure the age of a rock Radiometric Dating The History of Life  Radioactive isotopes that can be used for radiometric dating are found only in igneous or metamorphic rocks Fossil Evidence of Change Chapter 14

An isotope is a form of an element that has the same atomic number but a different mass number. Uranium 238 is an element commonly used to determine the age of rocks. When testing a rock sample, scientists calculate the ratio of the parent isotope to the daughter isotope to determine the age of the sample. i.e 206 with a half life of 4510 million years.When testing a rock sample, scientists calculate the ratio of the parent isotope to the daughter isotope to determine the age of the sample. i.e U238 decays to Pb 206 with a half life of 4510 million years. Carbon 14 is used to date organic substances such as bones and tissueCarbon 14 is used to date organic substances such as bones and tissue

 The geological time scale is a model that expresses the major geological and biological events in Earth’s history. The Geologic Time Scale The History of Life  The geologic time scale is divided into the Precambrian time and the Phanerozoic eon.  Eras of the Phanerozoic eon include the Paleozoic, Mesozoic, and Cenozoic eras.  Each era is divided into one or more periods Fossil Evidence of Change Chapter 14

Visualizing the Geologic Time Scale hill.com/olcweb/cgi/pluginpop.cgi?it=swf::550 ::400::/sites/dl/free/ /383925/CH1 4_Visualising_the_Geologic_Time_scale.swf ::Visualizing%20the%20Geologic%20Time% 20Scalehttp://glencoe.mcgraw- hill.com/olcweb/cgi/pluginpop.cgi?it=swf::550 ::400::/sites/dl/free/ /383925/CH1 4_Visualising_the_Geologic_Time_scale.swf ::Visualizing%20the%20Geologic%20Time% 20Scale

 Nearly 90 percent of Earth’s entire history, stretching from the formation of Earth to the beginning of the Paleozoic era about 542 million years ago Precambrian The History of Life  Autotrophic prokaryotes enriched the atmosphere with oxygen. Eukaryotic cells emerged, and the first animals had appeared.  Extensive glaciations marked 2 nd half of the Precambrian 14.1 Fossil Evidence of Change Chapter 14

 The ancestors of most major animal groups diversified in what scientists call the Cambrian explosion. The Paleozoic Era The History of Life  Life in the oceans continued to evolve at the end of the Cambrian period.  Fish, land plants, and insects appeared during the Ordovician and Silurian periods.  The first tetrapods emerged in the Devonian. i.e. Frogs  Mass extinction ended the era 14.1 Fossil Evidence of Change Chapter 14

The Mesozoic Era The History of Life  Mammals and dinosaurs first appeared late in the Triassic period, and flowering plants evolved from nonflowering plants.  Birds evolved from a group of predatory dinosaurs in the middle of the Jurassic period.  About 65 million years ago, a meteorite struck Earth. Evidence of this impact lies in the K-T boundary, which is a layer of rock Fossil Evidence of Change Chapter 14

The Cenozoic Era- The most recent era The History of Life  Mammals became the dominant land animals.  After the mass extinction at the end of the Mesozoic era, mammals of all kinds began to diversify Fossil Evidence of Change Chapter 14

 Plate tectonics describes the movement of several large plates that make up the surface of Earth. The History of Life  These plates, some of which contain continents, move atop a partially molten layer of rock underneath them Fossil Evidence of Change Chapter 14 Continental Drift

The History of Life Chapter 14 Continental Drift Video

Daily Objective Understand methods used to determine the age of rocks.

Radiometric Dating Link channel/ greatest-discoveries- radiometric-dating-video.htmhttp://videos.howstuffworks.com/science- channel/ greatest-discoveries- radiometric-dating-video.htm

Determine a Fossils Age Procedure: 1. Arrange pennies so that their “head sides are facing up. Each “head” represent an atom of K40, and each “tail” represents an atom of Ar Record the number of “heads” and “tails” present at the start of the experiment. Use the row marked 0 in the data table. 3.Cover the box and shake well. The shake represents ½ life of K40, which is 1.3 billion years.

4. Remove the lid and record the number of “heads” you see facing up. Remove all the “tail” pennies. 5. Complete Trial 1 by shaking and counting until you have reached 5 ½ lives. 6.Run two more trials and determine an average for the number of “heads” present at each half life. 7. Draw a graph. Plot your average values on the graph. Plot the number of half-lives for K 40 on the x-axis and the number of “heads” on the y-axis. 8. Remember, each half-life mark on the graph axis for K40 represents 1.3 billion years. 9.Remember a title and key for your graph!

For Extra Credit. Visit the website: ctive-dating-game Click on the green button: RUN NOW List 3 things that you didn’t know about dating fossils, that you now understand. List 2 things that you thought were neat about the site. List 1 thing that you would like clarified.

Daily Objective Differentiate between misconceptions about the origin of life.

14-2 Origin of Life Objectives Differentiate between spontaneous generation and biogenesis Sequence the events that might have led to cellular life Describe the endosymbiotic theory

14.2 The Origin of Life Origins: Early Ideas The History of Life  Spontaneous generation is the idea that life arises from nonlife.  Francesco Redi, an Italian scientist, tested the idea that flies arose spontaneously from rotting meat. Chapter 14

 The theory of biogenesis states that only living organisms can produce other living organisms. The History of Life  Louis Pasteur designed an experiment to show that biogenesis was true even for microorganisms The Origin of Life Chapter 14

Origins: Modern Ideas The History of Life  Simple organic molecule formation  The primordial soup hypothesis was an early hypothesis about the origin of life.  Organic molecules could have been synthesized from simple reactions.  UV light from the Sun and electric discharge in lightning might have been the primary energy sources The Origin of Life Chapter 14

 Stanley Miller and Harold Urey were the first to show that simple organic molecules could be made from inorganic compounds. The History of Life  The resulting mixture was found to contain amino acids- the building blocks for proteins. This supported the primordial soup hypothesis The Origin of Life Chapter 14 hill.com/sites/ /student_view0/ch apter26/animation_-_miller- urey_experiment.html

Making Proteins The History of Life  Life requires proteins.  One possible mechanism for the formation of proteins would be if amino acids were bound to a clay particle The Origin of Life Chapter 14

Genetic Code The History of Life  Some RNA sequences appear to have changed very little through time.  Many biologists consider RNA to have been life’s first coding system.  Other researchers have proposed that clay crystals could have provided an initial template for RNA replication The Origin of Life Chapter 14

Cellular Evolution The History of Life  Scientists hypothesize that the first cells were prokaryotes. Recall* prokaryotes are smaller than eukaryotes, and lack a defined nucleus. Many scientists think that modern prokaryotes called archaea are the closest relatives of Earth’s first cells The Origin of Life Chapter 14

Photosynthesizing Prokaryotes The History of Life  Archaea are autotrophic, and are considered to be the earliest forms of terrestial life.  They do not obtain their energy from the Sun. Archaea also do not need or produce oxygen.  They are extrempohiles The Origin of Life Chapter 14

The History of Life  Many scientists think that photosynthesizing prokaryotes evolved not long after the archaea.  Prokaryotes, called cyanobacteria, have been found in rocks as old as 3.5 billion years.  Cyanobacteria are aquatic bacteria, and manufacture their own food- photosynthetic The Origin of Life Chapter 14

The Endosymbiont Theory The History of Life  The ancestors of eukaryotic cells lived in association with prokaryotic cells.  The relationship between the cells became mutually beneficial, and the prokaryotic symbionts became organelles in eukaryotic cells.  This theory explains the origin of chloroplasts and mitochondria The Origin of Life Chapter 14

The History of Life 14.2 The Origin of Life Chapter 14