Anthropology Test Two Notes Polymorphism is the interaction between natural selection and mutation situation where there exists two or more alleles for a gene and at situation where there exists two or more alleles for a gene and at least two Polymorphism alleles have frequency greater than 1 28 of genes are polymorphic Polymorphism is due to natural selection acting on genetic variations caused by mutation Balanced polymorphism least two alleles have frequency greater than 1 Due to heterozygotes having higher fitness than homozygotes The frequency of the sickle cell allele is 5 15 in some areas Hemoglobin consists of two alpha and two beta polypeptide chains Each alpha chain has 141 amino acids each beta chain has 146 amino acids Sickle cell hemoglobin due to one point mutation affecting one amino acid in beta chain Malaria is caused by parasite transmitted between individuals by mosquito Uninfected RBCs do not sickle infected RBCs sickle and kill parasites Heterozygotes for sickle cell have lower rate of malarial infection compared to homozygotes for normal hemoglobin Heterozygotes for sickle cell have selective destruction of red blood cells Heterozygotes con conjointly supply oxygen to tissues and suppress parasitic proliferation In malarial environment heterozygotes for sickle cell have natural selective advantage over homozygotes for normal hemoglobin and sickle cell Because of heterozygote advantage alleles for both normal and sickle cell hemoglobin are maintained at high frequencies this is balanced polymorphism Evolution of balanced polymorphism for sickle cell Spread of slash and burn agriculture is related to natural selective advantage of sickle cell allele Thalassemia and G 6 PD deficiency are at polymorphic levels in some populations Natural selection is opportunistic selection acts on the phenotypic genotypic variability that exists in population Thursday 26 September 2013 Human Bio cultural Adaptation enzyme that allows you to digest lactose which is a sugar in milk deficiency in lactase Symptoms diarrhea nausea abdominal cramps gas Examples sickle cell and other red blood cell variants lactose sufficiency Lactose tolerance and intolerance Lactase Lactose intolerance Humans can digest milk as babies but most of us lose the ability after weaning Adults in some populations are lactose tolerant Populations with long histories of dairying are typically lactose tolerant Mutation for ability to digest milk as adults would have provided a natural selective advantage Human Variation Our species is polytypic Polytypism phenotypically different populations in a species Polytypism is result of diversity of environments that we inhabit Our populations diversify because of natural selection but our populations remain within a single species because of gene flow Race not a biologically useful grouping of humans Not useful in terms of evolutionary studies The appropriate unit of evolutionary study is population It doesn t tell you information Also it focuses on differences rather than similarities In science the point of grouping is that the similarities are magnified any beneficial modification that relieves environmental stress change in the structure of a gene pool as a result of natural selection Human Adaptation Adaptation Evolutionary perspective result of natural selection Human variation perspective and enhances survival of individuals Types of adaptations in hierarchical order Behavior learned Short term reversible acclimatization Developmental irreversible acclimatization Shivering of the body is proof that heat is being produced Tanning Hemoglobin at altitude Genetic result of natural selection Acclimatization as adaptation acclimatization occurs at the level of the individual Demonstrates the plasticity of human response to environmental stress We have a lot of different ways of adapting flexible All humans are capable of having these responses Acclimatization can be short term and reversible or developmental and irreversible Pigment is melanin Skin Pigmentation Melanin is produced in melanocytes which are in epidermis of skin Melanin is packaged into granules called melanosomes Melanosomes are transferred to keratinocytes which are also in epidermis Melanin functions to block ultraviolet radiation from penetrating skin and damaging DNA Genetic similarities between heavily and lightly melanized individuals All people have about the same number of melanocytes Genetic differences between heavily and lightly melanized individuals Produces more melanosomes Has larger melanosomes Compared to lightly melanized individual heavily melanized individual Melanosomes are more dispersed in keratinocyte Natural selective advantage to variation in skin pigmentation Dark skin pigmentation Adaptive in areas of intense ultraviolet radiation Melanin functions to absorb ultraviolet radiation Light skin pigmentation Adaptive in areas of low ultraviolet radiation Allows sufficient synthesis of vitamin D Reduces likelihood of skin cancer and degradation of folate Reduces likelihood of rickets Human adaptation to low temperature environments body shape Rule body mass is higher in areas with lower temperatures Rule length of arms and legs is shorter in areas with lower temperatures x3 x2 Bergmann s Allen s mass area Human adaptation to low temperature environments metabolism and blood flow Populations living low temperature environments show an extremities adaptation Higher basal metabolic rate Efficient vasoconstriction maintain higher temperature of fingers and toes Vaso means blood Constriction of blood vessels Populations living in high temperature environments show a hypothermic adaptation Lower basal metabolic rate Adaptation to low temperature environments Adaptations to low temperature environments by body shape metabolism and blood flow are developmental irreversible acclimatizations Adaptation to high altitude Hypoxia i e low atmospheric oxygen levels is a stress of high altitude Delivery of oxygen to tissues Oxygen transfers between compartments of the body by diffusion movement of gas from area of higher concentration to area of lungs blood cells Diffusion lower concentration Two variables influence rate of diffusion Concentration difference Surface area Reversible short term acclimatizations Hyperventilation Increase red blood cell production Increase in 2 3 DPG diphosphoglycerate Function increase concentration difference of oxygen between lungs and blood Function increase