Class updates Final - LAST WEEK OF SCHOOL: Tuesday, 6-5 Scantron - - PowerPoint PPT Presentation

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Class updates

Final - LAST WEEK OF SCHOOL: Tuesday, 6-5 Scantron 882-E (big one) and note paper for short answer questions 35 multiple choice questions; 10 true or false 5 short answer questions Content 9 questions - Ch. 1-5; 9 questions - Ch. 6-8; 27 questions - Ch. 9-13/14 ALLOWED A 3X5 NOTECARD

There's variation in ALL humans

• nonetheless our species is genetically closely related

Polytypic: species composed of local populations that differ from one another with regard to the expression of one or more traits Humans are a polytypic species

• geographically variable pattern among human populations

Gene pool: total complement of genes shared by the reproductive members of a population

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1. 4. 2. 3. 5.

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6. 7. 9. 8. 10.

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14. 15. 11. 12. 13.

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• 1. Australia, Oceania
• 4. India
• 2. North America,

Hopi Indian

• 3. Tonga, Oceania
• 5. Tibet

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• 6. San, Nambia, Africa
• 7. Japan, Asia
• 9. Kabil, Algeria
• 8. Evenki, Russia
• 10. Orissa, India

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• 14. Cambodia, Asia
• 15. Colombia, S. America
• 11. Yanomami, S. America
• 12. Oromo, Africa
• 13. Madagascar, Africa

• responses to environment
• natural selection
• struggle to maintain homeostasis

Homeostasis: interactions of physiological mechanisms maintain a balance in

• rganisms compensating for both external and internal changes

Stress - anything that pushes you out of your comfort zone

• anything that interferes with your ability to maintain homeostasis

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Why there are differences

Ultraviolet radiation (UVR) exposure

• most direct at the equator
• causes skin cancer
• depletes folate

Folate: a nutrient necessary to prevent neural tube birth defects Melanin: pigment responsible for the variations in human skin color

• more melanin = darker the skin
• acts as a natural sunblock
• skin filters out negative effects of UVR

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Different types of stress

Recall: lost fur and evolved in East Africa, i.e., an environment with lots of UVR Question: Why did migrants shift to lighter skin? Answer: Balancing act: stress of too much sunlight vs stress of too little sunlight

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Why there are differences

Darker skin: natural selection favored darker skin near the equator as a response to high levels of UVR

• prevents folate depletion
• decreases likelihood of neural tube defects during embryonic development

Lighter skin: natural selection favored lighter skin as humans moved to northern latitudes

• African migrants entered new environments, i.e., lower levels of UVR
• UVR interacts with skin to produce vitamin D which protects against rickets

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In sum...

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Skin pigment map

Adaptation: long-term evolutionary changes E.g., sweating Acclimatization: short-term physiological responses to environment

• responses to the environment that develop over an individual's lifetime

E.g., tanning

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Why of adjusting to our environment

Bergmann's Rule: bodies with increased mass or volume to surface area are

• ptimal for cold climates

Allen's Rule: appendages with decreased surface area are optimal for cold climates

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Bergmann's Rule: bodies with increased mass or volume to surface area are

• ptimal for cold climates

Allen's Rule: appendages with decreased surface area are optimal for cold climates

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*Variations due to responses to the thermal environment

• range: 120 degrees to -60 degrees for human populations

*Responses to hot thermal environments

• these are more effective = reflects our tropical origins
• ALL human populations = dissipate heat through evaporative

cooling Vasodilation: widening of capillaries to permit increased blood flow

• important mechanism for radiating body heat

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End of Ch 12

*Variations due to responses to the thermal environment

• ranges from 120 degrees to -60 degrees for human populations

*Responses to cold thermal environments Includes both heat retention and heat production Short-term responses to cold: increased metabolic rate, shivering, vasoconstriction Long-term responses to cold: prolonged vasoconstriction decreasing the risk of frostbite

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End of Ch 12

High altitudes - 25 million people live in altitudes 10,000 ft in the air Stressors: more intense UVR, cold, low humidity, wind, reduced nutritional base and hypoxia. Hypoxia: reduced availability to O2 Responses to hypoxia as a stressor: increased respiratory rate and heart rate, increased red blood cell production Developmental acclimatization: Tibetans undergo slower growth and maturation, possess larger chests, heart, more efficient diffusion of oxygen to body tissues

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End of Ch 12 start of Ch 13

Infectious diseases Exert a selective pressure on human populations Cultural factors play an important role in the spread of disease Until ~10 kya, we were small, nomadic hunter-gatherers who never occupied a location for long and rarely interacted with refuse heaps swarming with vectors Living in large, settled communities increased the transmission of diseases

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End of Ch 12 start of Ch 13

• exposure to domestic animals resulted in the spread of zoonotic diseases

(tuberculosis and influenza) Endemic diseases are ones that are continuously present in a population Pandemics are extensive outbreaks affecting large numbers of people over a wide area Today many bacterial diseases have reemerged: pneumonia, tb, cholera, and influenza (responsible for more human deaths than any other disease)

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End of Ch 12 start of Ch 13

Recall: humans are highly-generalized and behaviorally-flexible Rapid and dramatically environmental changes occurred relatively recently in our evolutionary history

• Our biology is mismatched with modern lifestyles
• leads to harmful consequences

ability to store fat used to be adaptive but maladaptive in industrialized societies

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Ch 13

Biocultural evolution and the life course Cultural factors interact with genetically-based biological traits

• influences how traits are expressed in individuals, e.g., IQ, body shape, and growth

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Ch 13

Our diets have changed dramatically over the past 10 kya Preagricultural diet: High in animal protein, complex carbs, and calcium Low in saturated fat and salt

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Diet and nutrition through the life course

Diabetes: disorder linked with decreased activity levels and increased consumption of fats and refined carbs

• another example of a maladaptation

Amino acids: 9 out of 22 amino acids are accessible only through dietary means

• the preagricultural diet made

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Diet and nutrition through the life course

Uniquely human:

• adolescent stage
• extended postreproduction in females

Childhood in humans

• long, key to learning in humans and vulnerable to human development

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Life stages in humans

Uniquely human: Menopause: period following the last menstrual cycle in females Grandmother hypothesis: might explain why there's menopause

• allowed for high-quality care for grandchildren

Senescene: decline in physiological functioning associated with aging

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Life stages in humans

Race concept

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*race is not scientifically useful when studying human variation *only a small fraction of our DNA comprises the "racial traits" *human population is better described as clinal Clines: a series of populations that display a continuous gradient of variation *Gene flow between populations results in no single genetically isolated human population *no single human population differs in adaptive phenotypic traits to even be a subspecies

• more variance in chimpanzee populations on opposite sides of a river than

between human populations

Race is still an important concept, it's just not a biological concept

• racial categories are INSTEAD socially constructed - racial categories are

influenced by human culture Makes sense given our understanding of biocultural evolution

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Biocultural evolution

• Humans live in a cultural environment

Sickle-Cell Trait: Selection favored malaria resistance

• agriculture introduced mosquito breeding sites to human populations ~2 kya

Lactose intolerance: Selection favored tolerance to milk products in pastoralists Cultural dependence on milk increased the frequency of lactose tolerance via natural selection

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Thermal environment

Responses to heat Evaporative cooling: all humans dissipate heat (sweating) Vasodilation: capillaries on the skin's surface widen to increase blood flow - radiates body heat