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Anatomy

Anatomy. Have Biology of Skin Color out with your answers. Biology Of Skin Color. (Sub-Saharan African, Indian, Southern European, and Northern European). There are no people who actually have true black, white, red, or yellow skin. 

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Anatomy

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  1. Anatomy • Have Biology of Skin Color out with your answers

  2. Biology Of Skin Color (Sub-Saharan African, Indian, Southern European, and Northern European)

  3. There are no people who actually have true black, white, red, or yellow skin.  • These are commonly used color terms that do not reflect biological reality.

  4. Very little of the skin is actually involved in skin-color difference.

  5. Pigmentation of Skin • Pigment (melanin) produced by melanocytes • Color is yellow to brown to black • Melanocytes are mostly in the stratum basale • Amount of melanin produced depends upon genetics and exposure to sunlight • Everyone has melanin. • The ONLY difference is the amount of melanin.

  6. Other Pigmentation Determinants • Carotene • Orange-yellow pigment from some vegetables • Hemoglobin • Red coloring from blood cells in dermis capillaries • Oxygen content determines the extent of red coloring

  7. Skin color and race • There are NO reliable genetic markers for race. (ie. There is no gene for race) • The concept of race is made-up. • The “false” concept of race can be traced to the history of European colonization- people really like to categorize. • As a species, all humans originated in Africa.

  8. Why have different shades? • Remember: we all share melanin production in the melanocytes at the lowest level of the epidermis. • Balance between protection against UV decomposition & use of UV to synthesize Vitamin D. • The skin uses UV light to synthesize vitamin D, ~1 hour a week is all that is needed.  • BUT, UV breaks down folic acid (Vitamin B) in the body.  • A lack of folic acid can lead to birth defects & deformed sperm

  9. Geography = Sunlight intensity! • Near the equator the amount of sunlight is much more than what is needed to synthesize vit D. • Too much exposure increases the risk of birth defects (lack of folic acid), defective sperm & skin cancer. • Thus, an increase in melanin (which absorbs UV and protects the folic acid & DNA) was selected for since humans with more melanin more likely to survive.

  10. Evolution of Skin Color • Evolution of humans near the equator in Africa benefited from an increase in the production of melanin. • BUT As people migrated, particularly far north of the equator (less intensity and length of light) the need for UV (vitamin D) outweighed the protection from destruction of folic acid & UV (birth defects & cancer).

  11. (Data for native populations collected by R. Biasutti prior to 1940.)

  12. Review your answers for # 1-5 of “Biology of Skin Color”. You should all have the same answers in general. • Then #6 & 6a- please discuss your answers as this is a more difficult question. As a group discuss 6a and try to come up with the best way to depict the relationship between UV, skin color and folic acid/folate/vit B • ON POSTER PAPER: create your final diagram of 6a. We will be hanging them in the room • 4. We will discuss 7-9 next class. • HW: Read Survival of the sickest and answer the questions.

  13. Have Survival of the sickest out AND bio of skin color. • 1st period- make a final diagram of your #6 based on your groups understanding. • 1st & 4th period- discussion about the articles • Lecture on cancer & burns • Begin disease reports • HW: research disease reports and WP #4 cancer and burns

  14. Diagramming complex ideas • A picture is worth a thousand words. • The idea behind this question is to turn a complicated hypothesis into an easier to understand picture. • Your challenge is to take your diagram as it is now

  15. Sun breaks down foliate. • High UV able to synth vit D Melanin protects foliate. High UV able to synth vit D Low UV still able to synth vit D for Ca absorption. No affect on foliate. Melanin blocks too much UV and skin cannot make vit D thus brittle bones. Low UV doesn’t affect foliate.

  16. Sun breaks down foliate. • High UV able to synth vit D Melanin protects foliate. High UV able to synth vit D Low UV still able to synth vit D for Ca absorption. No affect on foliate. Melanin blocks too much UV and skin cannot make vit D thus brittle bones. Low UV doesn’t affect foliate.

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