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Organism Orchestra, Part 1: How Do Species Change Over Time? After you have examined examples of the 5 kingdoms of living things and have seen variations in some of their physical characteristics, you will identify an adaptation of a given organism and then imagine, through a “Just So” story, how that adaptation may have come about. Be thinking about this question as you create your story: How did this particular organism come to have this special adaptation? Apply the 5step process by which populations may adapt and change over time to develop and write your story. Organism Orchestra, Part 1: How Do Species Change Over Time? Copyright 2007, Exemplars, Inc. All rights reserved. 1 of 13 Organism Orchestra, Part 1: How Do Species Change Over Time? Suggested Grade Span 6–8 Task After you have examined examples of the 5 kingdoms of living things and have seen variations in some of their physical characteristics, you will identify an adaptation of a given organism and then imagine, through a “Just So” story, how that adaptation may have come about. Be thinking about this question as you create your story: How did this particular organism come to have this special adaptation? Apply the 5-step process by which populations may adapt and change over time to develop and write your story. Big Ideas and Unifying Concepts Change and constancy Evolution and equilibrium Form and function Interdependence Life Science Concepts Evolution, diversity and adaptations Structure and function Mathematics Concepts Conclusions Data collection, organization and analysis Time Required for the Task One to two class periods. Context As part of a unit on the diversity of living things, students examined examples (live, prepared, videotaped, and still pictures) of the five kingdoms of living things. Students also examined how these samples showed variation in some of their physical characteristics. Students learned a generalized process by which populations may adapt and change over time, and that this Organism Orchestra, Part 1: How Do Species Change Over Time? Copyright 2007, Exemplars, Inc. All rights reserved. 2 of 13 process of evolution is how the diversity that we see in the living world has come to be. Finally (in Part 2), students were taught how to make and use bibliographic references, based on source material, to research and theorize about a specific animal’s evolutionary history. What the Task Accomplishes The task asks students to identify an adaptation of a given organism and then imagine how that adaptation may have come about. By doing so, students show that they understand how natural selection acts on populations. The task is designed to address Vermont’s Science/Mathematics/Technology Standard 7.13: Understanding the Role of Evolution. How the Student Will Investigate As a precursor to this assessment, I read the students several stories from Kipling’s Just So Stories. One story, “How the Elephant Got its Trunk,” was particularly well-received. I then went over with the students how the elephant might really have gotten its trunk – applying the following generalized, five-step process for how adaptations arise and spread: • There is a struggle for existence (competition, climate change, new predators, new prey, migration, etc.). • There is always variation in any population. • A variation (adaptation) may arise through a mutation that confers an advantage to individuals possessing that variation. • The advantage allows Individuals with the adaptation to reproduce more and/or produce more viable offspring. • As a result, the adaptation spreads in the population. Next, I asked students to think of other adaptations of living things and write a “story” using the five-step process, but clothing the story in “Just So” language. We reviewed stories and further clarified the five-step process, in preparation for the assessment task "Organism Orchestra, Part 2: How Do Species Change Over Time." Interdisciplinary Links and Extensions Science If, in another unit of study, your students are going to be studying Mendel, dominant and recessive genes and/or inheritance of genetic traits, you may want to make the connections between this inquiry (which provides a “big picture” generally of how animals and plants develop adaptations over a longer time) and the time and process it takes for generations of a living thing to pass on its traits. Research into variations of cats, dogs, etc., that are selectively bred for certain characteristics can provide a perspective on how human intervention alters this process. Organism Orchestra, Part 1: How Do Species Change Over Time? Copyright 2007, Exemplars, Inc. All rights reserved. 3 of 13 Language Arts Students may also wish to find and explore a range of other related literature (legends, folklore, science fiction and/or scientific theories). Social Studies There may be an appropriate unit of study in social studies/geography that can be taught in conjunction with this science unit, such as a study of the Galapagos Islands where Charles Darwin studied, among other living things, the 15 different tortoise species that developed on the different islands. Teaching Tips and Guiding Questions This is the essential question to ask students: How did the diversity of living things that we see in the world arise? A more specific version of this is, How did this particular organism come to have this special adaptation? Probably the most difficult concept for students to grasp is the notion of random variation in populations. Most often, they jump to the conclusion that if an organism “needs” an adaptation to survive it just “grows” that adaptation, rather than seeing that a particular variation may occur by chance mutation or recombination. I tried to avert this confusion by providing examples of how the students themselves vary (hand-span width, height, eye color, ear lobe attachment, etc.) and asking them how one of those variations may confer an advantage to someone possessing the variation. If I were to make this assignment again, I’d ask students to proofread story drafts with a peer and note numbers 1-5 as the reader found evidence of each of the five steps of the process. I think that this might help students achieve the Practitioner-level standard, by clarifying key aspects that needed to be addressed in their stories. Another alternative would be a prewriting graphic organizer for students to use in laying out their story elements. (This would also help the teacher to assess the students’ conceptual understanding and scientific reasoning in applying the five steps.) Concepts to be Assessed (Unifying concepts/big ideas and science concepts to be assessed using the Science Exemplars Rubric under the criterion: Science Concepts and Related Content) Life Science – Structure and Function: Students identify characteristics of organisms and explain how a certain adaptation has arisen and how species change over time. Life Science – Evolution, Diversity and Adaptations: Students hypothesize how the adaptations identified help the animals to survive in their particular habitats. Scientific Method: Students determine patterns and/or which kinds of change are happening over time (change and constancy). Organism Orchestra, Part 1: How Do Species Change Over Time? Copyright 2007, Exemplars, Inc. All rights reserved. 4 of 13 Mathematics: Students collect, organize and analyze data and draw appropriate conclusions. Skills to be Developed (Science process skills to be assessed using the Science Exemplars Rubric under the criteria: Scientific Procedures and Reasoning Strategies, and Scientific Communication Using Data) Scientific Method: Hypothesizing, using prior knowledge, using scientific reasoning, communicating findings, challenging misconceptions and raising new questions. Other Science Standards and Concepts Addressed Scientific Theory: Students look for evidence that explains why things happen and modify explanations when new observations are made. Life Science – Structure and Function; Regulation and Behavior; Populations and Ecosystems: Students describe and group living things into one of the five kingdoms. Students understand that each animal and plant has different structures that serve different functions in growth, survival and reproduction. Life Science – Evolution, Diversity and Adaptations: Students explain that species acquire many of their unique characteristics through biological adaptations, including changes in structures, behaviors or physiology that enhance their survival in an environment. Students understand how living things evolve. Students identify natural selection as the source of the diversity of living things. Suggested Materials Students might want reference sources on living things, such as encyclopedias, field guides, CD-ROM disks, books, “wildlife cards” (stacks of cards, each with pictures and descriptions of a species of living thing) and related children’s literature (legends, folk tales, etc.). Possible Solutions Students use the five steps as a guide for developing and writing their stories. They are expected to be accurate regarding the adaptation for the animal chosen and related habitat/ecosystem information. Their creativity, voice and tone come through in their writing style and in how they choose to elaborate their story. Most or all of the five-step process for how adaptations arise and spread should be clearly evident in the story. • There is a struggle for existence (competition, climate change, new predators, new prey, migration, etc.) • There is always variation in any population. • A variation (adaptation) may arise through a mutation that confers an advantage to individuals possessing that variation. Organism Orchestra, Part 1: How Do Species Change Over Time? Copyright 2007, Exemplars, Inc. All rights reserved. 5 of 13 • The advantage allows Individuals with the adaptation to reproduce more and/or produce more viable offspring. • As a result, the adaptation spreads in the population. Task-Specific Assessment Notes Novice The writing does follow the model of Just-So stories, yet while this is an engaging story, none of the required elements are present. Being “itchy”, for example, cannot be construed as a struggle for existence. The long tail variation does not arise by chance in an offspring of a shorttailed elephant. The selective advantage of the tail is not clear, and no indication is given of the spread of the variation in the population. There is no evidence of conceptual understanding. Apprentice In this story, the elements of an adaptation (ostrich’s legs) having an advantage, and the adaptation being passed down to offspring, are present, but no indication is given as to how the adaptation arose or that it arose by chance. Furthermore, the struggle for existence (eggs breaking) is only implied – and does not seem to be a sufficient force to drive the evolution of shorter legs. Practitioner Most of the elements (except the struggle for existence) are clearly present in this story,. It is not clear from the story that the student fully understands the necessity for the missing component. As well, the student’s writing implies that those who possess the new adaptation (long neck) are passing it on to their offspring. Since the story covers only six months of time, the reader cannot be certain that the student understands that only those with this adaptation would be passing it on – creating greater numbers with the adaptation and thus ensuring survival. Expert All of the steps in the process of natural selection are included in the story: struggle for existence, individual variation, selective advantage to variation, greater numbers of offspring, spread of variation in population. The writing is clear, detailed and coherent – cast in a whimsical fashion and writing style. Appropriate scientific terms and vocabulary enhance the student’s explanation. Connections are also made to survival in a specific habitat, to interdependence and to the food web. Organism Orchestra, Part 1: How Do Species Change Over Time? Copyright 2007, Exemplars, Inc. All rights reserved. 6 of 13 Novice Organism Orchestra, Part 1: How Do Species Change Over Time? Copyright 2007, Exemplars, Inc. All rights reserved. 7 of 13 Apprentice Organism Orchestra, Part 1: How Do Species Change Over Time? Copyright 2007, Exemplars, Inc. All rights reserved. 8 of 13 Practitioner Organism Orchestra, Part 1: How Do Species Change Over Time? Copyright 2007, Exemplars, Inc. All rights reserved. 9 of 13 Practitioner Organism Orchestra, Part 1: How Do Species Change Over Time? Copyright 2007, Exemplars, Inc. All rights reserved. 10 of 13 Practitioner Organism Orchestra, Part 1: How Do Species Change Over Time? Copyright 2007, Exemplars, Inc. All rights reserved. 11 of 13 Expert Organism Orchestra, Part 1: How Do Species Change Over Time? Copyright 2007, Exemplars, Inc. All rights reserved. 12 of 13 Expert Organism Orchestra, Part 1: How Do Species Change Over Time? Copyright 2007, Exemplars, Inc. All rights reserved. 13 of 13