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How to Use This Presentation To View the presentation as a slideshow with effects select View on the menu bar and click on Slide Show, or simply press.

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Presentation on theme: "How to Use This Presentation To View the presentation as a slideshow with effects select View on the menu bar and click on Slide Show, or simply press."— Presentation transcript:

1 How to Use This Presentation To View the presentation as a slideshow with effects select View on the menu bar and click on Slide Show, or simply press F5 on the top row of your keyboard. To advance to the next slide click the left mouse button once. From the Chapter screen you can click on any section to go directly to that sections presentation. Blank or missing areas of a slide will remain hidden until the left mouse button is clicked. You may exit the slide show at any time by pressing the Esc key Copyright © by Holt, Rinehart and Winston. All rights reserved.

2 The History of Life on Earth Chapter 8 Section 1: Evidence of the Past Section 2: Eras of the Geologic Time Scale Section 3: Humans and Other Primates Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

3 Evidence of the Past Section 1 Bellringer A mnemonic device is a trick that can help you remember words. Write down the four steps of natural selection. Then create a mnemonic device to help you remember each step by using the first letter of each step as the first letter of a word in a phrase that is easy for you to remember. Write your answer in your science journal. Copyright © by Holt, Rinehart and Winston. All rights reserved.

4 Evidence of the Past Section 1 Objectives Explain how fossils can be formed and how their age can be estimated. Describe the geologic time scale and the way that scientists use it. Compare two ways that conditions for life on Earth have changed over time. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

5 Evidence of the Past Section 1 Fossils Life Preserved in Rock Fossils are traces or imprints of living thingssuch as animals, plants, bacteria, and fungithat are preserved in rock. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

6 Evidence of the Past Section 1 Copyright © by Holt, Rinehart and Winston. All rights reserved. The Age of Fossils Life Preserved in Rock Estimating the age of rocks and fossils based on its position in sedimentary rock is called relative dating. Absolute dating is a method that measures the age of fossils or rocks in years. The next slide shows how half-lives can be used to date fossils. End of Slide

7 Using Half-Lives to Date Fossils Section 1 Copyright © by Holt, Rinehart and Winston. All rights reserved.

8 Evidence of the Past Section 1 The Geologic Time Scale Divisions of Time Paleontologists have divided the geologic time scale into large blocks of time. Mass Extinctions Some of the important divisions in the geologic time scale mark times when rapid changes happened on Earth. During these times, many species died out completely, or became extinct. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

9 Evidence of the Past Section 1 The Changing Earth Pangaea German scientist Alfred Wegener proposed that long ago the continents formed one landmass, which he called Pangaea, surrounded by a gigantic ocean. Do the Continents Move? In the mid-1960s, J. Tuzo Wilson of Canada came up with the idea that huge pieces of the Earths crust were pushed around by forces within the planet. His theory is illustrated on the next slide. Adaptations to Slow Change When conditions on the Earth change, organisms may adapt or become extinct. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

10 Moving Continents and Tectonic Plates Section 1 Copyright © by Holt, Rinehart and Winston. All rights reserved.

11 Eras of the Geologic Time Scale Section 2 Bellringer Suppose that electrical energy was never developed. How would your life differ from what it is like now? What kinds of games and toys do you have that work without electricity? Do you think you would be miserable or would you still have plenty of ways to have fun? Write your answers in your science journal. Copyright © by Holt, Rinehart and Winston. All rights reserved.

12 Eras of the Geologic Time Scale Section 2 Objectives Outline the major developments that allowed life to exist on Earth. Describe the types of organisms that arose during the four major divisions of the geologic time scale. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

13 Eras of the Geologic Time Scale Section 2 Precambrian Time Copyright © by Holt, Rinehart and Winston. All rights reserved. How Did Life Begin? Scientists think that life developed from simple chemicals in the oceans and in the atmosphere. Photosynthesis and Oxygen The first cyanobacteria began to release oxygen gas into the oceans and air. Eventually, some of the oxygen formed a new layer of gas in the upper atmosphere. Multicellular Organisms After about 1 billion years, organisms that were larger and more complex than prokaryotes appeared in the fossil record. End of Slide

14 Eras of the Geologic Time Scale Section 2 The Paleozoic Era Copyright © by Holt, Rinehart and Winston. All rights reserved. When Was the Paleozoic Era? The Paleozoic era began about 543 million years ago and ended about 248 million years ago. Life on Land During the 300 million years of the Paleozoic era, plants, fungi, and air-breathing animals slowly colonized land. End of Slide

15 Eras of the Geologic Time Scale Section 2 The Mesozoic Era Copyright © by Holt, Rinehart and Winston. All rights reserved. Life in the Mesozoic Era Dinosaurs are the most well known reptiles that evolved during the Mesozoic era. The Extinction of Dinosaurs At the end of the Mesozoic era, 65 million years ago, dinosaurs and many other animal and plant species became extinct. End of Slide

16 Eras of the Geologic Time Scale Section 2 The Cenozoic Era Copyright © by Holt, Rinehart and Winston. All rights reserved. The Age of Mammals The Cenozoic era is sometimes called the Age of Mammals. Mammals have dominated the Cenozoic era the way reptiles dominated the Mesozoic era. The Cenozoic Era Today We are currently living in the Cenozoic era. Modern humans appeared during this era. End of Slide

17 Humans and Other Primates Section 3 Bellringer Understanding evolution requires recognizing similarities and differences. What makes you unique among your family members? What makes you recognizable as part of your family? Are all these traits physical or are some behavioral? Write your answer in your science journal. Copyright © by Holt, Rinehart and Winston. All rights reserved.

18 Humans and Other Primates Section 3 Objectives Describe three characteristics that all primates share. Describe three major groups of hominids. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

19 Humans and Other Primates Section 3 Primates Copyright © by Holt, Rinehart and Winston. All rights reserved. The First Primates The ancestors of primates may have coexisted with the dinosaurs. Apes and Chimpanzees Scientists think that the chimpanzee, a type of ape, is the closest living relative of humans. A comparison of a human and ape skeleton is shown on the next slide. Hominids Humans are in a family separate from other primates. This family, called hominids, includes only humans and their human-like ancestors. End of Slide

20 A Comparison of Primate Skeletons Section 3 Copyright © by Holt, Rinehart and Winston. All rights reserved.

21 Humans and Other Primates Section 3 Hominids Through Time The Earliest Hominids The earliest hominids had traits that were more humanlike than apelike. Australopithecines Many early hominids are classified as australopithecines. A Variety of Early Hominids Some australopithecines had slender bodies. Some early hominids had large bodies and massive teeth and jaws. Global Hominids About 2.3 million years ago, a new group of hominids appeared. These new hominids were members of the group Homo. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

22 Humans and Other Primates Section 3 Recent Hominids Neanderthals One recent hominid is known as Neanderthal. Neanderthals lived in Europe and western Asia. Early and Modern Humans Modern humans are classified as the species Homo sapiens. The earliest Homo sapiens existed in Africa 100,000 to 150,000 years ago. Drawing the Hominid Family Tree Scientists now speak of a tree or even a bush to describe the evolution of various hominids in the fossil record. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

23 The History of Life on Earth Chapter 8 Concept Map Copyright © by Holt, Rinehart and Winston. All rights reserved. Use the following terms to complete the concept map on the next slide: geologic time scale, mammals, Mesozoic, paleontologists, Cenozoic, eukaryotes, relative dating, absolute dating, Paleozoic, dinosaurs, Precambrian.

24 Concept Map Chapter 8 Copyright © by Holt, Rinehart and Winston. All rights reserved.

25 Concept Map Chapter 8 Copyright © by Holt, Rinehart and Winston. All rights reserved.


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