Organism Orchestra, Part 2: How Do Species Change Over Time?

Transcription

1 Organism Orchestra, Part 2: 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 theorize how that adaptation may have come about. Be thinking about this question as you work: How did this particular organism come to have this special adaptation? Use your prior knowledge about the 5-step process by which populations may adapt and change over time (and other references sources) to develop your theory. 1 of 11

2 Organism Orchestra, Part 2: 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 theorize how that adaptation may have come about. Be thinking about this question as you work: How did this particular organism come to have this special adaptation? Use your prior knowledge about the 5-step process by which populations may adapt and change over time (and other references sources) to develop your theory. 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 2 of 11

3 process of evolution is how the diversity that we see in the living world has come to be. Finally, students were taught how to make bibliographic references based on source material. What the Task Accomplishes This 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. I used one story, How the Elephant Got its Trunk to explain how the elephant might really have gotten its trunk identifying a 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. Part 1 of this task ("Organism Orchestra, Part 1") asked students to write a story applying the five-step process, using Just So language. After we reviewed stories and further clarified the five-step process, I gave the students the Organism Orchestra assessment task sheet (Part 2). The students were given an index card with the name of an organism on it. They were asked to make use of the resource materials provided (encyclopedias, CD-ROM disks, etc.) to find information about their organism. A specific piece of information for the students to obtain was a description of any special adaptations. As the final step in the assessment, students were asked to describe using the five-step process learned earlier a theory about how the adaptation might have arisen and spread in the species. 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 3 of 11

4 bred for certain characteristics can provide a perspective on how human intervention alters this process, in a much-shortened time frame. Language Arts Part 1 provides a literature link and story-writing component as the lead-up to this inquiry task. Conventions regarding bibliographic references are important in writing reports in all fields of study. Students should be asked to appropriately identify sources used in their narrative and technical writing. 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 avoid 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. 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). Mathematics: Students collect, organize and analyze data and draw appropriate conclusions. 4 of 11

5 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: Observing, 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 To get students started, prepare index cards with names of animals to be researched. (Although prepared cards may seem to limit student choices, it ensures that there will be adequate reference materials for them to use in finding appropriate information.) Students will need reference sources on living things, such as encyclopedias (print and CD), field guides, CD-ROM disks, books and wildlife cards (stacks of cards, each with pictures and descriptions of a species of living thing usually animals). Sometimes, a local college or museum will provide access to resource people with expertise in this area as well. Possible Solutions Students use the assessment form given to them. This has places for them to respond to each of the questions asked. Students should identify and explain the adaptation, cite resources for their information, and use the five steps as a guide for their explanations. 5 of 11

6 Task-Specific Assessment Notes Novice The student does not complete the task. S/he does not identify an adaptation or else does not address how the adaptation may have arisen. Although some research is completed, the student does not attempt to apply the five steps to his/her explanation evidence of lack of understanding the scientific reasoning and concepts being studied. Bibliographic references are sketchy, at best. The student said, I think that the tarsier evolved from the monkey. It likes to climb trees and practically lives in them. Take the adhesive discs on the bottom of the feet. This enables them to climb trees easy and catch its food. Monkeys also have special grips on the bottom of their feet. They both live in trees and have special feet to help them out in life. Apprentice The student correctly identifies an adaptation of the organism ( The pelican has a pouch on the bottom section of its beak that it uses to catch fish with. ) and gives an explanation of how the adaptation may have arisen, but fails to provide detail. Some, but not all, of the steps in the process of natural selection are identified, and examples of each are given evidence of applying some scientific reasoning and knowledge of interdependence. Many students fail to identify random variation in populations as the source from which adaptations arise and instead imply (or actually state) that the organism needed to evolve that adaptation and so it did. This demonstrates limited conceptual understanding. The student said, The pelican might have needed to catch larger fish because the smaller ones died. Their small bills weren t big enough so the pelicans adapted and grew pouches so they could catch and hold large fish. The pelicans with the large pouch variation had an advantage over the small beaked birds. The large pouched pelicans produced more offspring and the frequency of the variation increased. Eventually all pelicans had pouches on their beaks. Practitioner The student correctly identifies an adaptation of the organism ( The Rhea has a long neck, powerful legs and their strong wings. ) and gives an explanation of how the adaptation may have arisen, but fails to provide detail. Most of the steps in the process of natural selection are identified, and examples of each are given. This student s explanation does identify random variation in the population as the source of the adaptation (a rhea was born with a longer neck) evidence of conceptual understanding and scientific reasoning. Connections are also made to survival in a specific habitat and to the interdependence of plants and animals. The student said, The Rhea proble (sic) wasn t as tall as it is now. Something in nature might have change how high the plants are in South America. If the plant vegetation gets higher then Rhea s would have to change and either get bigger legs or longer necks. One rhea was born 6 of 11

7 with a longer neck. That one had a better health and had offspring which also had long necks. Then all the Rhea s had long necks. Expert The student correctly identifies an adaptation of the organism ( It has armlike forelegs with sharp hooks. ) and gives a clear, detailed explanation of how the adaptation may have arisen. All of the steps in the process of natural selection are identified, and examples of each are given. Connections are also made to survival in a specific habitat and to the interdependence of plants and animals. Appropriate scientific terms and vocabulary enhance the student s explanation. The student said, A long time ago mantids had a short smoothe (sic) forelegs. It was very hard to catch food this way. Eventually, their primary food source dwindled. Mantids had to work extra hard to get food. One day a grove (?) of eggs hatched and they all had rather long, spikey forearms. This generation was much more successful at catching food with its long arms. These mantids were well fed. They got more food than all of the others. These healthy mantises were quickly chosen as mates. The gene that mutated the mantises forearms was passed on to the eggs that they laid. This kept up and the gene spread in the population. Now mantids are completely evolved with spikey forearms. 7 of 11

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