Bio Anthropology Lecture 9 Notes
Bio Anthropology Lecture 9 Notes ANTH1013 001
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This 4 page Class Notes was uploaded by pcoliver96 on Tuesday February 16, 2016. The Class Notes belongs to ANTH1013 001 at University of Arkansas taught by Lucas Delezene in Winter 2016. Since its upload, it has received 35 views. For similar materials see Introduction to Biological Anthropology in ANTH at University of Arkansas.
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Date Created: 02/16/16
University of Arkansas ANTH 1013 – Intro to Biological Anthropology Delezene Bio Anthropology: Lecture 9 Notes (notes going towards exam 1) What do we need for evolution to occur? -biological evolution: a change in allele frequency over time -allelic variation is needed (heritable variation) -alleles are constantly being created by mutations -once variation is present, genetic drift, gene flow, and natural selection take over -can humans evolve? YES Geographic variation among humans: skin color -the amount and distribution of melanin, a pigment, causes the variation we observe in skin tones -melanin: a dark brown to black pigment occurring in the hair, skin, and iris of the eye in people and animals Skin color variation: UV radiation -UV radiation: -shows a latitudinal gradient –being most intense at the equator and weakening in intensity towards the poles -shows an elevational gradient – being more intense at higher altitudes -induces mutation in skin – leads to skin cancers -dark skin acts as a natural sun block -the role of UV radiation: folate destruction: -destroys folate – important chemical for cells when they’re rapidly dividing **women are often advised to take folate supplements during pregnancy Sunlight and vitamin D production -there is at least one benefit associated with exposing skin to the sun -vitamin D is manufactured in the skin when struck by the sun University of Arkansas ANTH 1013 – Intro to Biological Anthropology Delezene -if dark skin reflects radiation more effectively than light skin, then does light or dark skin manufacture vitamin D more readily? Skin color distribution: the big picture -skin color is a balancing act between the evolutionary demands of photo - protection and the need to create vitamin D in the skin -we can buffer vitamin D deficiencies with diet Bio cultural evolution: lactose digestion -lactose (milk sugar) is broken down by the enzyme lactase -the typical state (phenotype) for adult humans and all other mammals is to not be able to digest milk sugar is lactose intolerant -gradually stop manufacturing lactase after the weaning period -weaning: accustom (an infant or other young mammal) to food other than its mother's milk Lactase persistence and natural selection -high frequency of lactase persistence associated with cultures that frequently consume milk -adaptation has evolved multiple times independently Bio cultural evolution: sickle-cell trait and malaria -according to some estimates, malaria has been the number one infectious killer of humans throughout our evolutionary history -recently as of 2004, 1.8 million people are estimated to have died from malarial infection -sickle-cell hemoglobin protects from malarial infection Natural selection and malaria -heterozygote advantage: the heterozygotes have a higher fitness than either homozygote -balanced polymorphism: stable frequencies of alleles Natural selection: human body size & shape -Allen’s rule: endotherms from cold regions have shorter limbs than populations from warmer regions -Bergmann’s rule: endotherms in cold regions tend to be larger in body size than those from warmer regions -cold-adapted populations tend to be shorter and stockier with shorter limbs University of Arkansas ANTH 1013 – Intro to Biological Anthropology Delezene -warm-adapted populations tend to be taller, more linear, and have longer limbs **the difference in body shape relates to heat loss -in tropical climates, human body shape is adapted for losing heat -in cold climates, human body shape is adapted to retain heat Human biological variation: genetic drift -old order Amish trace their ancestry to as few as 200 German immigrants, and they don’t practice exogamy with other groups -have experienced a lot of genetic drift and rare traits elsewhere are now common -Ellis-van Creveld syndrome -PKU: incidence in non-Amish is about 1/10,000 – for Amish it’s about 1/1,000 -the colony of Tristan de Cunha was founded by 15 people in 1814 – one of them was heterozygous for a recessive disorder called retinitis pigmentosa -today the frequency of that allele in the descendants is 10x higher on Tristan than in the UK Examples of genetic drift: -Ashkenazi Jews formed a fairly isolated gene pool in Europe with little exogamy -their descendants have elevated frequencies of some rare traits -Tay-Sachs syndrome: 1/25 Ashkenazi Jews are estimated to be carriers of the recessive allele Human biological variation: gene flow -African American populations have rates of European admixture of up to 25% in the US Human variation: special patterns in allele frequencies -cline: the gradual change in allele frequency across space Acclimatization -acclimatization is not the same as adaptation -adaptation: the outcome of natural selection – population’s gene pool evolved to meet the demands of the environment -acclimatization: a change of an individual’s phenotype in response to changing environment conditions University of Arkansas ANTH 1013 – Intro to Biological Anthropology Delezene -in response to decreasing partial pressure of oxygen at high altitudes, the body responds by producing more red blood cells SAMPLE QUESTIONS + ANSWERS • Which of the following is true of dark -skinned people? -they have lower rates of UV radiation induced mutations than light-skinned people, they have reduced rates of folate destruction compared to light-skinned people, they have a reduced ability to produce vitamin D compared to light-skinned people (all of the above) • Which of the following “rules” states that endotherms from colder climates tend to be larger in body size than their tropical relatives? -Bergmann’s rule • The gradual change in allele frequency across space is known as… -a cline • The elevated frequency of Ellis-van Creveld syndrome in old order Amish is an example of… -the founders effect
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