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 1
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 2
1. 2. 3. 4. 5. 3
6. 7. 8. 10. 9. 4
11. 12. 13. 14. 15. 5
1. Australia, Oceania 2. North America, 3. Tonga, Oceania Hopi Indian 4. India 5. Tibet 6
6. San, Nambia, Africa 7. Japan, Asia 8. Evenki, Russia 10. Orissa, India 9. Kabil, Algeria 7
11. Yanomami, S. America 12. Oromo, Africa 13. Madagascar, Africa 14. Cambodia, Asia 15. Colombia, S. America 8
Why there are differences -responses to environment -natural selection -struggle to maintain homeostasis Homeostasis: interactions of physiological mechanisms maintain a balance in organisms 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 9
Different types of stress 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 10
Why there are differences 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 11
In sum... 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 12
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Skin pigment map 14
Why of adjusting to our environment 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 15
Bergmann's Rule: bodies with increased mass or volume to surface area are optimal for cold climates Allen's Rule: appendages with decreased surface area are optimal for cold climates 16
Bergmann's Rule: bodies with increased mass or volume to surface area are optimal for cold climates Allen's Rule: appendages with decreased surface area are optimal for cold climates 17
End of Ch 12 *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 18
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 19
End of Ch 12 start of Ch 13 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 20
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 21
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) 22
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 23
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 24
Diet and nutrition through the life course 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 25
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 26
Life stages in humans Uniquely human: - adolescent stage -extended postreproduction in females Childhood in humans -long, key to learning in humans and vulnerable to human development 27
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 28
Race concept *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 29
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 30
Biocultural evolution - Humans live in a cultural environment 31 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
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
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