Bergmann s Rules Adaptations for Malarial Protection HbS allele Alpha Thalassemia Among mammals of similar shape the larger ones lose heat less rapidly than the smaller ones Among mammals of similar size more linear organism will lose heat more rapidly than the non linear organism o Demonstrates the effect of the surface area to volume ratio is important G6PD Mahidol deficiency variant Allen s Rules Gloger s Rules Mammals in cold climates tend to have shorter and bulkier limbs allowing lower body heat loss Mammals in hot climates have long slender limbs allowing higher body heat loss More heavily pigmented human populations tend to be found near the equator The Southern Hemisphere tends to be slightly darker than the Northern counterpart Clinal Distribution of latitude to skin pigmentation Thomson s Nose Wide noses in hot wet climates and narrow noses in cold dry climates greater surface area to moisten heat air Confers protection against P falciparum P falciparum unknown with P vivax P vivax not P falciparum How Reduces parasite density limits disease progression Limits disease progression Reduces parasite density Phenotype A B AB O Genotypes AA AO BB BO AB OO Antigens A B A B None Antibodies Anti B Anti A None Anti A Anti B Forces of Evolution Natural selection selection acts on the phenotype Mutation random change in DNA sequence ultimate source of variance but wont greatly change allele frequencies alone Coupled for max effect on evolution Gene flow exchange of genetic material between two populations Reduces variation between populations but increases variation within them Can spread mutation Can be migration and or hybridization Determined by environmental cultural factors geographic distance Impact depends on size of population duration of contact gene frequency differences bet Pops Gene flow is the natural consequence of marriage mating patterns and it maintains species integrity H W Equilibrium Fundamental theory to identify change in genotype and allele frequencies assumptions no forces of evolution random mating Important Mutations Genes to Know Observed genotype count allele frequency genotype frequency p 2 AA Aa 2 q 2 aa Aa 2 CCR5 the past and HIV resistance today is a byproduct infinite population size random sampling Lactase persistence p2 AA 2pq Aa selection for the mutant allele for resistance to some other infectious disease in allele frequency expected genotypic frequency Malnutrition Kwashiorkor change in hair color edema in stomach legs Marasmus death Reduced brain growth Deficiency of protein Failure to grow Deficiency of protein and calories Starve to o Populations with high rates of LP N Europeans pastoralist African populations Arabian peninsula q2 o What are the selection pressures Pastoralism o How did this adaptation arise Point mutation Relying on animals for a large amount of caloric intake water in dry regions being able to digest the lactose in milk is very advantageous o What type of evolution is this Convergent evolution variance arose on highly divergent haplotype backgrounds This is directional selection because it is mendelian Selecting for dominant allele Skin Color Gloger s rule is that skin color is related to latitude clinal distribution o o Selective effects of UV radiation leading to dark skin Sunburn skin cancer protects against damaging effects of UV radiation on folate levels resistant to infection Light skin vitamin D absorption Main source of vitamin D is sun Migrating from the equator UV radiation decreases and with too much melanin Rickets MS immune function energy conservation producing melanin takes up a lot of energy High altitude o Hypoxia uv radiation cold and dry fewer sources of nutrition o acclimate short term increased respiration hyperventilation loss of appetite loss of sensory ability last for several days increased production of red blood cells last for several months acclimatize long term respiration and RBCs count return to normal o o Developmental plasticity developmental acclimatization younger you move more effects larger lung capacity lager right ventricle delayed maturation puberty increase in chest dimension Not hereditary o Genetic mechanisms Tibetans have lived thousands of years in altitudes above 4500 m hemoglobin concentrations maintained at the sea level status quo