Keystone Species in an Ecosystem Using Connection Circles to Tell ...

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IntroductionEcosystems are built upon complex interrelationships among organisms and their habitats. Often,a change in the population of one species causes unexpected changes in other species.Understanding and representing a web of changes is challenging for the scientists who study them,let alone for readers who try to comprehend these complex situations. In this lesson, studentsread a chapter from a skillfully written science book and use connection circles to unravel amystery of nature. 1As in previous lessons, students will frame their inquiry with these questions: What is changing?How is it changing? Why is it changing?Materialso Overhead projector or display boardo Several different colored markers for each studento Connection Circle template for each student (page 15)o Posted copy of “Connection Circle Rules” (page 16)o Copies of “The Case of the Twin Islands” from The Shape of Change (2008), page 137.How It WorksIn her informative and entertaining book, The Case of the Mummified Pigs and OtherMysteries in Nature, 2 Susan E. Quinlan has written fourteen true stories that describe theresearch of ecologists who puzzle out how and why ecosystems behave as they do. Readersdiscover the interesting and often surprising connections among organisms through the work ofdetectives who find clues to nature’s riddles.The chapter, “The Case of the Twin Islands,” examines why the ecosystems in the waters off twoneighboring Aleutian Islands are so different. As students use connection circles to trace causalrelationships in the story, they discover the role of a keystone species, a species vital to thestability of the whole ecosystem. Students learn how feedback loops maintain a delicate balancein an ecosystem and what happens when that balance is disturbed.Connection CirclesThe purpose of a connection circle is to help students focus on the problem presentedby the author and to uncover its causes. Here is a quick overview:o First, students briefly define the problem: What is the author concerned about?What is the main problem? What is changing over time?o Next, how is it changing? In a few words, or with a quick behavior over timegraph, students describe how the problem is increasing or decreasing over time.o Finally, students look for elements in the story that contribute to the problem.They use a connection circle to organize their thoughts, find cause and effectrelationships, and trace the feedback loops that tie them together to explain whythe problem occurs.2
Procedure1. Read “The Case of the Twin Islands,” reprinted with permission in the Appendix of TheShape of Change (2008) beginning on page 137. Students may read independently, sharereading, or listen to it read aloud.2. Create connection circles summarizing the situation described in the story. If students aredrawing connection circles for the first time, follow the procedure detailed in Lesson 10, “Do YouWant Fries with That?” in The Shape of Change (available from www.clexchange.org).If students are already familiar with connection circles, give each student a Connection CircleTemplate (page 15), review the rules, and ask pairs of students to begin choosing elements fortheir circles. See the Appendix (page 16) for a larger copy of the rules to post in your classroomfor easy reference.CONNECTION CIRCLE RULES1. What’s the problem: What is changing? How is it changing?2. Choose elements of the story that satisfy all of these criteria:o They contribute to the problem.o They are nouns or noun phrases.o They increase or decrease over time.3. Write your elements around the circle. Include no more than 5 to 10.4. Find elements that cause another element to increase or decrease.o Draw an arrow from the cause to the effect.o The causal connection must be direct.5. Look for feedback loops. Tell their story.3. What’s the problem? What is changing? Ask students to quickly identify the problem that theauthor is presenting. They may say, “The sea otters have disappeared from the waters aroundShemya while the sea urchin population has grown there.”Ask students to define the problem more precisely by describing how the populations changedover time in a graph or briefly in words. These are examples on the following page. They are justquick rough sketches of the general patterns of behavior. (Students may prefer to sketch separategraphs for each population.)3
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Page 5 and 6: Precise language and clear thinking
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Page 9 and 10: Sea Urchins and KelpHere is another
Page 11 and 12: one loop. Most stories contain over
Page 13 and 14: Fur traders hunted sea otters to th
Page 15 and 16: Connection Circle Template1. What
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