The Sun, Natural Selection, and Skin Color Prepared by Kathia Rodriguez [email protected] June 26, 2014 This material was produced for Excellence in Curricula and Experiential Learning (EXCEL) Program, which is funded through UNT Sustainability. The University of North Texas holds the copyright. This material is available for use under a Creative Commons Attribution-­‐NonCommercial 3.0 Unported License. Title Prepared By Original Creation Date Version Date of Current Version Revised By Description Rights Information Licensing Information Document Information The Sun, Natural Selection, and Skin Color UNT Sustainability June 26, 2014 1.0 June 26, 2014 A collection of activities and resources regarding the sun, natural selection, and skin color that meet state education standards and national sustainability standards for the 8th grade level. ©University of North Texas This work is licensed under a Creative Commons Attribution-­‐
NonCommercial 4.0 International License. Revision History Previous Version Changes none Natural Selection and Skin Color The Sun, Natural Selection, and Skin Color Table of Contents Introduction .......................................................................................................... 1 Grade Level .............................................................................................. 1 Discipline .................................................................................................. 1 TEKS ......................................................................................................... 1 National Education for Sustainability Learning Standards ....................... 1 Objective .................................................................................................. 2 Keywords ................................................................................................. 2 Description of Activities ........................................................................... 2 Activities ................................................................................................................ 3 Activity 1: Understanding Skin Color ....................................................... 3 Introduction ................................................................................... 3 Materials ........................................................................................ 3 Products ......................................................................................... 3 Process ........................................................................................... 3 Activity 2: Evolution of human traits ....................................................... 5 Introduction ................................................................................... 5 Materials ........................................................................................ 5 Products ........................................................................................ 5 Process .......................................................................................... 5 Additional Resources ............................................................................................ 8 Online Resources ....................................................................................... 8 Handouts “The Human Spectrum” “Native Peoples, Skin Tones, and Latitudes”
Natural Selection and Skin Color Excellence in Curricula and Experiential Learning 1 Introduction Grade Level These activities are intended for a sixth grade classroom. Discipline These activities have a science and social studies focus. TEKS Content: Organisms and environments. In studies of living systems, students explore the interdependence between these systems. Interactions between organisms in ecosystems, including producer/consumer, predator/prey, and parasite/host relationships, are investigated in aquatic and terrestrial systems. Students describe how biotic and abiotic factors affect the number of organisms and populations present in an ecosystem. In addition, students explore how organisms and their populations respond to short-­‐ and long-­‐term environmental changes, including those caused by human activities. TEKS §112.18. Science, Grade 6. (a)(4)(E) Throughout social studies in Kindergarten-­‐Grade 12, students build a foundation in history; geography; economics; government; citizenship; culture; science, technology, and society; and social studies skills. The content, as appropriate for the grade level or course, enables students to understand the importance of patriotism, function in a free enterprise society, and appreciate the basic democratic values of our state and nation as referenced in the Texas Education Code (TEC), §28.002(h). TEKS §113.20. Social Studies, Grade 6. (a)(5) Skills: The student knows that interdependence occurs among living systems and the environment and that human activities can affect these systems. TEKS §112.20. Science, Grade 8. (b)(11)(A)(B)(C)(D) The student understands the physical characteristics of North America and how humans adapted to and modified the environment through the mid-­‐19th century. TEKS §113.20. Social Studies, Grade 8. (b)(11)(A)(B)(C) The student understands the relationships between and among people from various groups, including racial, ethnic, and religious groups, during the 17th, 18th, and 19th centuries. TEKS §113.20. Social Studies, Grade 8. (b)(23)(A)(B)(C)(D)(E) National Education for Sustainability K-­‐12 Student Learning Standards 2.4 ~ Social and Cultural Systems ~ Cultural Diversity Natural Selection and Skin Color Excellence in Curricula and Experiential Learning 2 Objective Students explore their own cultural identity and the identity of their peers and people in their community and the different views and values that each culture brings to the community. Key Words Race Latitude Traits Ancestors Evolution Ultraviolet radiation Natural selection Pigmentation Description of Activities The following activities have been compiled to address the topic of “Studying Food” in sixth grade classrooms. The activities meet the state and national education standards for sixth grade, and are intended to supplement pre-­‐existing curricula, with a focus on integrating sustainability topics. The activities can be used in conjunction or alone. Natural Selection and Skin Color Excellence in Curricula and Experiential Learning 3 Activities Activity 1: Understanding Skin Color Introduction In this activity, students will learn about the local multiplier effect, and through an interactive website, handouts, and class discussion, will learn that money spent on local products is money that stays in and benefits that community. Materials Computer Projector Products Discussion Process 1.
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Display to the class the page of facial portraits taken in Berlin, Germany as part of FACITY (http://www.facity.com/berlin/), an online photo project. Scroll slowly down the page through the nearly 600 facial portraits, so that students can see all of them. Ask what facial features vary among people. There are many possible answers and include: eye color, shape of nose or lips, type of chin, thickness and shape of eyebrows, degree of wrinkles, amount and type of facial hair, shape and texture of lips, and skin color. Click on several individual photos to enlarge them. Ask students to focus on skin color as they answer these questions: • For any one person, is skin color the same all over? The correct answer is no; no one has evenly pigmented skin. •
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What are some of the ways that skin color varies on a person’s face? Answers may include: some people have skin that is darker or lighter in sections; some have freckles, moles, scars, or other spots Now tell the students you will ask them a question that they should answer based on their own experience: •
Considering all the people in your family, all the people of your community, and all the people of the world, how does skin color vary? Answers may include: skin colors range from pale to dark; skin colors range in tone from pink to olive; some people have relatively smooth skin tones and others have skin that is more unevenly colored. Keep probing until someone mentions that skin color also varies depending on time of year and exposure to the sun. Natural Selection and Skin Color Excellence in Curricula and Experiential Learning 4.
4 Say to the class that they’ve mentioned a lot of the ways that skin color varies within a person, within a family and community, and within all humanity. One of those ways that you mentioned is very important: skin color varies based on exposure to the sun. Sunlight not only affects skin color from one day to the next; it also has affected the evolution of skin color among the peoples of the world. In this lesson, we’ll learn something about how the process of natural selection over many generations has protected peoples of the world from too much or too little sun exposure. Natural Selection and Skin Color Excellence in Curricula and Experiential Learning 5 Activity 2: Evolution of Human Traits Introduction Students will learn about natural selection. They will look at different categories that humans are grouped by. They will discuss how and why skin and other traits develop over time. Materials Handout-­‐ “The Human Spectrum” Computers Printer Products Visual display Short story Power point Drawing Process 1.
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Begin by having students use their “The Human Spectrum” Handout to visit The Human Spectrum, which is a section of the website, Race: Are We So Different (http://www.understandingrace.org/humvar/spectrum.html). This interactive page teaches about the continuum of human traits and the arbitrary ways in which people divide up such continuums to categorize each other. Assign students in groups to review The Human Spectrum website and to discuss the questions on the student handout. Have each group assign a note taker and a reporter. After the small groups have completed this task, reconvene the class as a whole to discuss each question: •
From Slide 1: Short, medium, and tall is one way we categorize people. There are many others. For example: young, middle-­‐aged, and old. Ø
What are some other ways people commonly categorize each other? Ø
What are the advantages and disadvantages of grouping people in the ways you have named? •
From Slide 6: “Skin tones overlap both within and between native peoples.” Ø Give an example using the named peoples from the graph of native peoples. For example: Although Holy Island people as a whole are lighter-­‐skinned than Sherpa people, some Sherpa individuals are lighter-­‐skinned than some Holy Island individuals. Ø
What does it mean for the concept of race if the quoted sentence is true? Natural Selection and Skin Color Excellence in Curricula and Experiential Learning 6 Ø
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Do you think race is a good way to group people? Answers may vary. Encourage students to explain their answers. Use the last question to transition. Ask students to define race. Answers will vary; an example is a group of humans that shares distinct physical characteristics. Explain that race is difficult to define because it is a “social construct”—it is based on arbitrary groupings such as by skin color, with arbitrary cut-­‐off points between one group and another: “The idea of races supposes that there are natural breaks in the distribution of human biological variation that produce clear clusters (or races) of people who share certain traits. However, the opposite is generally true: human variation is a continuum.” Now students should read Only Skin Deep, a second section from the website (http://www.understandingrace.org/humvar/skin_01.html). When they have read the material, reinforce the concepts presented by discussing these questions: •
What was the challenge for the human body when our early ancestors moved into hot, open places such as grassy savannahs, in search of food and water? (They were exposed to the hot sun.) •
How did they evolve in response? (They lost hair and gained more sweat glands, which were adaptations that enabled their bodies to stay cool.) What was the challenge for the human body as it evolved away from body hair and more skin became exposed? (They were more vulnerable to ultraviolet radiation of the sun.) •
•
What is a benefit of ultraviolet radiation for the human body? (It helps the human body make vitamin D, which the body must have to absorb the calcium necessary for strong bones.) •
How does ultraviolet radiation challenge the human body? (Too much ultraviolet radiation can destroy another vitamin called folate [folic acid], which is essential to the development of healthy fetuses.) •
Where is ultraviolet radiation the strongest? (It is strongest nearest the equator.) •
How did natural selection work to bring about the trait of darker skin in people who live near the equator? (Pigmentation was selected for, because it protected the body from too much penetration by ultraviolet radiation. In this way, the body’s store of folate was protected. At the same time, year-­‐round exposure to strong sun ensured that the body could produce enough vitamin D. Folate and vitamin D are important for creating healthy babies. People with more pigmented skin were more likely to successfully reproduce, passing on their traits [including the trait of pigmented skin] to the next generation.) •
How did natural selection work to bring about the trait of lighter skin in people who live far from the equator? (Pigmentation was selected against, so that the body could absorb enough ultraviolet radiation to obtain vitamin D, which is necessary for maternal and fetal bone strength. People with strong bones were more likely to live to adulthood so that they could reproduce, passing on their traits [including the trait of less pigmented skin] to the next generation.) Natural Selection and Skin Color Excellence in Curricula and Experiential Learning •
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7 Why is the threat of skin cancer from ultraviolet radiation not a plausible explanation for why dark skin evolved in peoples who lived near the equator? (Skin cancer usually affects people after they have had children, so it is not likely to have had an effect on which traits were passed on.) As a follow-­‐up project to this learning, assign students to each investigate one of the peoples named in the sixth slide of The Human Spectrum. Ask them to do the following: • Find some facts about the culture of their assigned people • Locate the latitude at which that people has traditionally lived. • Find and print out a photograph of one or more representative members of that people. Students can collect this information on the Native Peoples, Skin Tones, and Latitudes student handout. •
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Ask students to write a hypothesis to explain how natural selection has worked to evolve differences in another human biological trait besides skin color. Then, imagine that a physical change were to occur to Earth (ozone layer allows more sun to get in, land starts rapidly eroding, etc.), and envision what new characteristic might evolve in humans in response to this change. This hypothetical trait should be realistic and have some scientific proof behind it (for example, students should not hypothesize that humans’ skin will grow paler if their exposure to the sun is increased). Students should design a project illustrating this “new” human trait. Ideas include: •
•
Have students work together to place the worksheets on a wall according to latitude, to create a visual display of the correlation between latitude and skin color. •
•
A drawing showing the trait. A short story describing the advantages/disadvantages of the trait told from the point of view of an individual who has developed it. A power point explaining how the new trait helps humans Etc. Natural Selection and Skin Color Excellence in Curricula and Experiential Learning 8 Additional Resources Online Resources Primary Source http://sciencenetlinks.com/lessons/sun-­‐natural-­‐selection-­‐and-­‐skin-­‐color/ Reference Resources http://www.understandingrace.org/home.html http://www.understandingrace.org/humvar/skin_01.html http://www.understandingrace.org/humvar/spectrum.html Natural Selection and Skin Color The Human Spectrum
INTRODUCTION
In this lesson, you will explore how the sun’s intensity at different latitudes has contributed to
variation in human skin color. Use the resources on The Human Spectrum website
(http://www.understandingrace.org/humvar/spectrum.html) to help you answer these questions.
The Human Spectrum: Where Do You Draw the Line?
Slide 1
Short, medium, and tall is one way we categorize people. There are many others. For
example: young, middle-aged, and old. What are some other ways people commonly categorize
each other? What are the advantages and disadvantages of grouping people in the ways you
have named?
Slide 6
“Skin tones overlap both within and between native peoples.” Give an example using the named
peoples from the graph of native peoples. For example: Although Holy Island people as a whole
are lighter-skinned than Sherpa people, some Sherpa individuals are lighter-skinned than some
Holy Island individuals. What does it mean for the concept of race if the quoted sentence is true?
Do you think race is a good way to group people?
Only Skin Deep
What was the challenge for the human body when our early ancestors moved into hot, open
places such as grassy savannahs, in search of food and water?
How did they evolve in response?
What was the challenge for the human body as it evolved away from body hair and more skin
became exposed?
What is a benefit of ultraviolet radiation for the human body?
How does ultraviolet radiation challenge the human body?
Where is ultraviolet radiation the strongest?
How did natural selection work to bring about the trait of darker skin in people who live near the
equator?
How did natural selection work to bring about the trait of lighter skin in people who live far from
the equator?
Why is the threat of skin cancer from ultraviolet radiation not a plausible explanation for why dark
skin evolved in peoples who lived near the equator?
Native Peoples, Skin Tones, and Latitudes
INTRODUCTION
Now is your opportunity to investigate one of the peoples named in the sixth slide of The Human
Spectrum interactive. Find some facts about the culture of your assigned people and locate the
latitude at which that people has traditionally lived. Also find and print out a photograph of one or
more representative members of that people.
Name of the People:
Where they live:
Degrees latitude___________________________ North or South (circle one)
Some facts about this people:
Source for the above:
Photo images
Source for photo image and caption provided (if any) at the source:
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