Skin Color and Geography  QOD: How would you describe the distribution of skin color around the world, based on what you know? Consider the skin color of indigenous populations, in other words, people who evolved where they currently live and haven’t migrated (voluntarily or otherwise) in the last 500 years. Why do you think skin color has the pattern it has?

Solar radiation worldwide

Which explains… …why these people evolved near the equator.

And… …why these people evolved in the north

…but it doesn’t explain …why these people evolved in the most northern latitudes in the world (the arctic circle)

Skin Color and Geography  Humans, like all species, are subject to the laws of evolution and natural selection  Evolutionary fitness depends on reproductive success  You have to live long enough to have babies to reproduce  Q: What is the reproductive advantage of having dark skin where UV light is more intense? What is the reproductive advantage of having light skin where UV light is less intense? What about the Inuits?  Humans, like all species, are subject to the laws of evolution and natural selection  Evolutionary fitness depends on reproductive success  You have to live long enough to have babies to reproduce  Q: What is the reproductive advantage of having dark skin where UV light is more intense? What is the reproductive advantage of having light skin where UV light is less intense? What about the Inuits?

Skin Color and Geography  Each team gets a set of cards. Divide the cards into 2 piles: 1) cards that give facts about advantages of darkly pigmented skin 2) cards that give facts about advantages of lightly pigmented skin  Make 2 columns in your I.N. (INPUT page) for each group or cards and record the information that belongs in each column  Once you have gathered and recorded all the information given, Write a 1 paragraph explanation (on binder paper, to be turned in) for the pigmentation of Northern Europeans, West Africans and the Inuit and other people of the Arctic circle.  Each team gets a set of cards. Divide the cards into 2 piles: 1) cards that give facts about advantages of darkly pigmented skin 2) cards that give facts about advantages of lightly pigmented skin  Make 2 columns in your I.N. (INPUT page) for each group or cards and record the information that belongs in each column  Once you have gathered and recorded all the information given, Write a 1 paragraph explanation (on binder paper, to be turned in) for the pigmentation of Northern Europeans, West Africans and the Inuit and other people of the Arctic circle.

Physiology: T 10.4  TCB  Video group: please send me an explaining exactly which parts of the project you were responsible for. (this is separate from the weekly assignment)  GOALS/AGENDA  Review yesterday’s activity, write or complete paragraph explanation.  Structure & function of skin  TCB  Video group: please send me an explaining exactly which parts of the project you were responsible for. (this is separate from the weekly assignment)  GOALS/AGENDA  Review yesterday’s activity, write or complete paragraph explanation.  Structure & function of skin

The integumentary system  Includes skin, hair, nails and glands  Functions  Protection (UV, injury, infection)  Vitamin D production  Temperature regulation  Holds in moisture  Sense organ  Removes wastes  Includes skin, hair, nails and glands  Functions  Protection (UV, injury, infection)  Vitamin D production  Temperature regulation  Holds in moisture  Sense organ  Removes wastes

The skin has 2 layers  Epidermis:  Outermost  Origin of glands, hair follicles, glands  Mostly epithelial  Growth and cell division at deepest part pushes cells outward  Outermost epidermis is dead, flattened cells which flake away  Many keratinocytes which make keratin for waterproofing  Melanocytes make melanin  Epidermis:  Outermost  Origin of glands, hair follicles, glands  Mostly epithelial  Growth and cell division at deepest part pushes cells outward  Outermost epidermis is dead, flattened cells which flake away  Many keratinocytes which make keratin for waterproofing  Melanocytes make melanin

Skin color  Melanin provides basic lightness or darkness  Equal numbers of melanocytes, difference is in how much melanin they produce  Other pigments: carotene, hemoglobin  Melanin provides basic lightness or darkness  Equal numbers of melanocytes, difference is in how much melanin they produce  Other pigments: carotene, hemoglobin

The skin has 2 layers  Dermis:  Deeper than epidermis  Connective tissue  Tough and strong- collagen fibers  Flexible- elastin fibers  Can separate from epidermis, space fills with fluid…blister. Ouch.  Contains blood vessels and nerves  Dermis:  Deeper than epidermis  Connective tissue  Tough and strong- collagen fibers  Flexible- elastin fibers  Can separate from epidermis, space fills with fluid…blister. Ouch.  Contains blood vessels and nerves

Exocrine Glands  Secrete substances that leave the body through ducts  Found w/in dermis but derived from epidermis (epithelial)  Sebaceous gland: produces oil, found near hair follicles  Sweat gland: temperature regulation & chemical signals  Secrete substances that leave the body through ducts  Found w/in dermis but derived from epidermis (epithelial)  Sebaceous gland: produces oil, found near hair follicles  Sweat gland: temperature regulation & chemical signals

Sweat  Made of: water, dissolved salts, wastes, other substances  2 types of sweat  Stimulated by temperature  Stimulated by stress, pain, hormones  Made of: water, dissolved salts, wastes, other substances  2 types of sweat  Stimulated by temperature  Stimulated by stress, pain, hormones

Oil  Sebum  Sebaceous glands found everywhere except palms of hands and soles of feet  Softens and lubricates skin and hair, helps kill bacteria and keep skin from cracking  Sebum  Sebaceous glands found everywhere except palms of hands and soles of feet  Softens and lubricates skin and hair, helps kill bacteria and keep skin from cracking

Hair  Keratinized cells  Growth at the root  Straight or curly depends on angle of follicle and shape of hair shaft  Keratinized cells  Growth at the root  Straight or curly depends on angle of follicle and shape of hair shaft

Below the Skin  Deeper than the dermis is the layer called the hypodermis  Technically not considered part of skin  Primarily adipose and connective tissue  Deeper than the dermis is the layer called the hypodermis  Technically not considered part of skin  Primarily adipose and connective tissue

Sweaty fingers  What happens when you have to talk in front of a large group?  Sweaty palms?  Find out what else makes you sweat.  Notebook  Title  Purpose  Observations (follow to do and notice)  Interpreting your observations Qs  What happens when you have to talk in front of a large group?  Sweaty palms?  Find out what else makes you sweat.  Notebook  Title  Purpose  Observations (follow to do and notice)  Interpreting your observations Qs

Examining structure of skin  View slides of scalp, draw in notebook  Line up slide so that epidermis is visible at the edge  label epidermis, dermis, follicle, hair shaft, sebaceous gland, sweat gland, any other structures you can find  take your time- make these the best microscope drawings you’ve ever done. Use colored pencil, draw individual cells and tissue layers  Make sure labels point inside the field of view and clearly point to structures  Will be graded separately when notebooks are collected  View slides of scalp, draw in notebook  Line up slide so that epidermis is visible at the edge  label epidermis, dermis, follicle, hair shaft, sebaceous gland, sweat gland, any other structures you can find  take your time- make these the best microscope drawings you’ve ever done. Use colored pencil, draw individual cells and tissue layers  Make sure labels point inside the field of view and clearly point to structures  Will be graded separately when notebooks are collected

Physiology: W 10.5  TCB  Homework check  Movie  Assessments  GOALS/AGENDA  Sweaty fingers  Finish skin presentation  TCB  Homework check  Movie  Assessments  GOALS/AGENDA  Sweaty fingers  Finish skin presentation