ANP 202 Biocultural Evolution Lecture 8 Human Adaptation to Environmental Extremes Big Questions How do people adapt to environmental extremes and other circumstances? Adaptations to temperature Humans must maintain a constant body temperature around 98.6°F to survive. What are the examples of adaptations to extreme temperatures? Adaptations to cold stress Cultural: Shelter, clothing, work scheduling, ? Physiological : Shivers/goosebumps vasoconstriction Developmental adaptations: Higher skin temperature Adaptations to heat Cultural: Shelter, clothing, work scheduling, etc. Physiological: Sweating, vasodilation Climate and Morphological Variation a general relationship exists between climate and body size and shape in all warm-blooded species Bergmann?s Rule predicts that mammals in cold climates tend to have large body Allen?s Rule predicts that mammals in cold climates tend to have short, bulky limbs, allowing less loss of body heat Population variation in body shape In COLD regions Expect large body (torso) sizes Relatively short limbs In HOT regions Expect smaller body (torso) sizes Relatively long limbs Body shape Bergman?s Rule Allen?s Rule Skin Human skin is naked and sweaty Adaptations to solar radiation 1. Solar radiation consists of different light energies, including ultra violet radiation or UVR 2. UVR is both a blessing and a curse: it is necessary for our body synthesize vitamin D for bone formation it destroys folate (one of the B vitamins) necessary for DNA synthesis it damages cells and cause melanomas Adaptations to solar radiation 3. How do humans adapt to UVR? Skin Melanocytes Adaptation to UVR ?Skin Deep? by Jablonski & Chaplin Effects on vitamin D UVR increases production of VD Effects on folic acid UVR degenerates folic acid Vitamin D 90% of VD is synthesized in the skin and kidneys from UVR VD is needed for intestines to absorb calcium and phosphorus SO, we need UVR BUT? Too much UVR breaks down folic acid (folate, a B vitamin) Too much UVR? Loss of folic acid?. Neural tube defects in babies of pregnant women Sperm cell defects among males Skin cancer SO, selection for dark skin in high UV environment UV effects on DNA Too little UV light? Not enough vitamin D production affects use of Calcium?. rickets and osteoporosis (bone defects affect birth canal) heart function blood clotting SO, selective pressure for light skin in low UV environments Rickets osteoporosis For the most part skin color is darkest in populations that live at the equator and lighter in populations that live farther away This reflects genetic adaptation to the varying intensity of UVR in different environments Natural selection is responsible for the differences that we see in skin color in modern humans Test Yourself 1. In 1775, the German anatomist Blumenbach: Discovered the existence of DNA Categorized skulls into 5 races Used blood types to classify races Showed that skull shape change over time Test Yourself 2. Robert Lewontin: Discovered that most genetic variation is found between human races Discovered most genetic variation is found within population Test Yourself 3. A cline: Is continuous variation that follows geographic gradients Describes the pattern of occurrence of trisomy 18 Describes the pattern of variation in skin color in relation to latitude A & D Test Yourself 4. The second trimester of human prenatal development involves mainly: Organ development Rapid growth in length A & B Weight gain Test Yourself 5. Human brain growth is completed by age: One Three Six Ten Test Yourself 6. DNA: Largely determines development from conception through death Schedules growth, but environment and events influence actual development Is the sole influence on growth and development None of the above Test Yourself 7. Humans adaptations to low oxygen levels in high altitudes includes: physiological adaptation such as increased production of_________, developmental adaptation of increased __________, and genetic adaptation of______________. Oxygen, RBC size, hemoglobinopathy Hemoglobin saturation; lung size; sickle-cell trait RBCs; lung size; hemoglobin saturation RBCs; nose size; sickle-cell trait T/F 8. Functional adaptations in humans during their lifetimes are usually associated with environmental condition T/F 9. Functional adaptations serve to alter internal homeostasis
Want to see the other 31 page(s) in Human Adaptation Lecture 1.ppt?JOIN TODAY FOR FREE!