Encyclopaedia Britannica Discovering Dinosaurs Teacher Guide



		Where Did Everybody Go? (Grades 6-8) Activity 3 You may have noticed that there are no dinosaurs around these days. In fact, there haven't been any around for about 66 million years. At the end of the Cretaceous Period, there was a mass extinction that killed off the last of the dinosaur species and many other living things. While extinction is a normal part of evolution, it usually happens to a species over a long period of time. Animals gradually become extinct when more of a species die than are born. A mass extinction, on the other hand, is much faster. A large number of species all over the world die out very suddenly, at least in terms of geologic time. At the end of the Cretaceous Period, about half of all life forms died out, including all the remaining dinosaurs. What happened to cause all these wonderful animals to disappear? No one knows for sure, but there are some strong theories. Work with a group to find out everything you can about one of the theories listed on this page. Then imagine you are at a scientific conference on the causes of the dinosaur extinction. Present and defend your theory in a debate with other "scientists." The Main Theories Yow! A Giant Asteroid Boom! Another Volcano Erupts Brrr! The Climate Changes Blam! A Supernova Explodes Ah-choo! Disease Strikes Objectives Students will use the Discovering Dinosaurs Spotlight and other Internet resources to research one of five theories about the causes of the mass extinction at the end of the Cretaceous Period. Students will demonstrate their understanding by participating in a classroom scientific conference on dinosaur extinction theories. Students will be able to explain the nature of a scientific theory, and explain why evidence sometimes leads scientists to disagree about theories.	CORRELATIONS TO NATIONAL SCIENCE EDUCATION STANDARDS CLASSROOM MANAGEMENT ASSESSMENT/EVALUATION TEACHINGTIPS ADDITIONALRESOURCES BACK TO TEACHER GUIDE CONTENTS
		CORRELATIONS TO NATIONAL SCIENCE EDUCATION STANDARDS top of page Grades 5-8 Content Standard A: Science as Inquiry Think critically and logically to make the relationships between evidence and explanations Recognize and analyze alternative explanations and predictions Content Standard C: Life Science Diversity and adaptations of organisms Content Standard D: Earth and Space Science Earth’s history Content Standard G: History and Nature of Science Science as a human endeavor Nature of science CLASSROOM MANAGEMENT top of page Divide the class into five groups. Assign one theory to each group. The conference is done as a class. Explain the format for the conference before students begin. First come the opening remarks: each team in turn presents its assigned theory and the evidence supporting that theory. Nonpresenting teams listen quietly and take notes. After each team has presented its theory, a question-and-answer period begins. The teacher or another "neutral" person moderates the discussion. During this time, teams challenge the theories supported by other teams by asking questions that point out a theory’s weaknesses. In response, each team defends its assigned theory by answering these questions in such a way as to highlight the theory’s strengths. Wrap up the conference by asking students, as a class, to vote for the theory that seems most likely to them, based on supporting evidence. Students do not have to vote for the theory assigned to their own teams. ASSESSMENT/EVALUATION top of page Teams that have researched their assigned theory and presented it well will include a clear, concise description of their extinction theory in their opening remarks present the fossil, geologic, and other evidence that supports their assigned theory, including pictures and diagrams where helpful reply to challenges from other teams by referring to the scientific evidence that supports their assigned theory challenge other teams by citing scientific evidence that is not explained by that team’s theory The above guidelines are for team evaluations. Individual evaluations should be based on the student’s contribution to the group effort, and on the student’s effectiveness at oral presentation. Skills Development: thinking critically, researching, comparing and contrasting hypotheses TEACHING TIPS top of page Arrange for all teams to have a total of 1½-2 hours of access to Internet resources. Before students begin their online research, encourage them to understand what they are looking for and to write down a few questions to answer as they search. For example, "What have scientists found in rocks that supports our team’s theory?" Scientific theories go in and out of style based on the evidence available to support them and on the ideas of the scientists currently working in that field. At present, the asteroid theory is the most popular, and the team working on it will have the easiest time finding information. Remind students who have the other theories that there are strong arguments for their theories, too. Their challenge is to present those strengths and to point out weaknesses in the rival theories. Point out to students that they do not have to agree with the theory they are researching and defending. In fact, it is helpful to understand the strengths of the other theories in order to challenge them. Emphasize the importance of supporting scientific ideas (hypotheses and theories) with scientific evidence (data). In the case of dinosaur extinction, evidence takes the form of fossils, rock layers, landforms, ocean sediments, and related materials. The strongest hypothesis or theory is the one that explains the majority of the available data and accurately predicts new data. Encourage each team to give all of its members a chance to speak during the conference. For example, one member may present the theory, another may present the evidence for the theory, a third may ask questions of the other teams, and others could answer questions after consulting with team members. ADDITIONAL RESOURCES top of page This section contains links to an online bookstore, Amazon.com, which will enable you to order many of the titles listed below. For adults Alvarez, Walter, *T. rex and the Crater of Doom* is the Princeton University Press, 1997 version. (Also available in paperback.) An accessible and credible presentation by one of the scientists who first proposed the asteroid-impact theory. Bakker, Robert T., *The Dinosaur Heresies: New Theories Unlocking the Mystery of Dinosaurs and Their Extinction.* Kensington Pub. Corp., 1996. Renowned paleontologist Bakker challenges theories of how dinosaurs lived as well as how they became extinct. Page, Jack, and Charles B. Officer, *The Great Dinosaur Extinction Controversy.* Perseus Press, 1996. The authors oppose the asteroid-impact theory and present an alternative explanation for dinosaur extinction. Powell, James Lawrence, *Night Comes to the Cretaceous.* W.H. Freeman & Co., 1998 "Mr. Powell describes the whole debate [on the asteroid-impact theory] in a text that deals well with the inevitable technicalities." (The Atlantic Monthly)