Download Organism Orchestra, Part 1: How Do Species Change Over Time?

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?
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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?
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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.
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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).
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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.
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• 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.
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Novice
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Apprentice
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Practitioner
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Practitioner
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Practitioner
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Expert
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Expert
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