Anthropology Notes PDF

​ Blending theory of inheritance ​ Gregor Mendel (1822 - 1884) ​ Breeding experiments on strains of peas which were pure for 7 different discreet combinations ​ 28,000 plants; 400,000 seeds ROUND + WRINKLED (pure) = All ROUND (self-...

​ Blending theory of inheritance ​ Gregor Mendel (1822 - 1884) ​ Breeding experiments on strains of peas which were pure for 7 different discreet combinations ​ 28,000 plants; 400,000 seeds ROUND + WRINKLED (pure) = All ROUND (self- fertalized) 3/4 ROUND, ¼ WRINKLED ​ NO blending ​ There are physical units of inheritance that maintain their identity when passed form parents to offspring (genes) ​ Dominant, recessive ( codominance) ​ Locus: physical location of genes ​ Alleles: different forms of the same gene ​ Homozygote( pair of same allele) , heterozygote ( pair of different alleles) ​ Genotype ( specific combination of allele), phenotype ( gene= morphological result of alle combination) ​ Monogenic trait= determined by one gene; such traits are discrete ​ Polygenic trait= inflcluenced by multiple genes; such traits are continuous ​ polymorphism = existence of 2 or more alles at a locus and thus 2 or more genotypes at that locus ​ Chromosomes ○​ Containers of DNa ○​ 23 pairs of chromosomes( 1 from each parent) in each human cell= 46 total  ○​ Meiosis= cell division in gemr cells producsinh gamhetes( egg cell, sperm); sperm + egg cell -> zygote ○​ mitosis= cell dicision in all other cells ​ DNA ○​ Humans= 21,000 genes ​ Produces at least 100,000 proteins= a primary function of genes. ​ = 2-3% of all DNA directly and consistently involved in protein production ​ DNA without a clear purpose used to be called junk DNA but is now understood as the location of regulatory genes ○​ Only 25% of dna is considered junk dna ​ Noncoding RNA ​ Epignetics ○​ Changes in Dna structure that dont involve changes in base sequence ○​ Methylation ○​ Response to stressfull environment ○​ Can affect expression ofn at least some genes; e.g. regulatory ○​ At least some are transmitted to offspring ​ Exons (coding), introns (non-coding) ​ Second category: regulatory genes ​ Multiple operating but in different possible combinations ​ enhancers , silencers ​ Homeobox= Hox genes ○​ Codon= 3 consecutive bases= smallest genetic unit of functional information ​ Each codon codes for a specific amino acid = units which make up protiens; I.e codon sequencwe deterimines amino acid sequence -> protien structure-> protien function ​ One gene- one protein model ○​ Located in chromosomes in nucleus of all cells ○​ Double helix; backbone =phosphate + sugar= deoxorhybose ○​ rungs= pairs of bases ​ Adenine + thymine ​ Cytosine + Guanine ​ Evolution= change in the frequency of alles in a breeding population from generation to generation ○​ Forces of evolution ​ Mutation  ​ Ulitimate source of all new genetic variation = change in the seuqence of DNA bases ​ Meiosis ​ spontaneous mutation rate; mutagens ​ Occurrence of mutations is random ​ Mutations rare ​ Once believed that almost all mutations in current species were deleterious= decreased probability of survival ​ gel electrophoresis: detects differences between individuals in the amino acid dequence of the same protein; indirect assessment of genotype ​ About 25-30% of all protein-producing loci are polymorphic in a wide variety of species ​ Explanation: natural selection is not operating; i.e, one for, of the protein is not more efficient than another ​ Neutral mutation: changes in codon sequence which are neither advantageous nor deleterious ​ Now appears that neutral mutations are not as prevalent as once thought ​ Drosophila ○​ Appears 20% of junk actually being acted uponby natural selectionction at very low intensity ○​ Only 5% appears to be neutral ​ Evelitionary importance of neutral mutations* ○​ Increases the importance of drift ○​ May provide an advantage in the future ​ 13 rabbits introduced into australia in 1859; 600 million by 1940 ○​ Myxamatosis virus introduced to curtail population. ○​ Virgin population not exposed to virus ○​ Rabbits possessing neutral mutations more likely to survive; virus also became less virulent ​ Gene flow ​ Movement of individuals from one breeding population to another ​ Mate exchange ​ Effects on genetic variation ○​ Increased genetic diversity within breeding population ○​ Decreased genetic difference between breeding populations ​ Natural selection ​ Must be a stress resulting in differential mortality; often this involves relatively small differences between groups of individuals in probability of survival ​ Individuals who are best able to cope with the stresses of their enviroment ​ Types ○​ Directional ​ Polygenic trait: ​ Peter and Rosemary Grant: medium ground finch in galapagos ○​ Much larger Variability in beak size compared to other finches ​ 1976: birds tagged and weighed; 5 inches of rain (normal) ​ 1977: 1 inch of rain: no breeding and 85% of medium ground finches died ​ 1978: back to 5 inches of rain ○​ Suvival not random; larger birds more likely( no guarantees) to survive ​ Plants prodicing large seeds tend to live in low-lying areas where there is greater access to ground water and more likely to survive then plants producing small seeds which tend to live in high lying areas ​ Increase in seed size = increase in seed toughness ○​ Process: ​ Larger birds have larger and stronger beaks ​ Superior biological design for this specific environment ​ Better adapted ​ Larger average body size next generation  ○​ What happemded with return to normal levels of rainfall ​ Gradual decrease in average body size until 1983 ○​ El nino: 8 months of rain -> flooding ○​ Small seeds are consumed more effectively by sma,l birds which increases chance of survival and decreases body size ○​ Enviromemts sometimes remain fairely constant on average over long periods of time but there can still be considerable environmental fluctuation over a short period of time which can result insubstantialgenetic chnage ​ Monogenic trait (discrete phenotype): ​ Peppered moth; 1848: color dterminee by 1 locus= monogenic; 1% black, 99% mottled gray; loght colored lichen on tree trunks ​ Industrial revolution: dark moths had a 15% greater chance of survival ​ 1898：> 98% were black ​ Clean air act pattern reversed ○​ Stabalizing selection ​ Monogenic traits: (discrete phenotype)= balanced polymorphism ​ Heterzygote is better adapted than both homozygotes ​ As a result, both alleles are maintained in the populations at some stable rate, depending on magnitude of difference eon probability of survival ​ Polygenic trait: (continous phenotype) individuals with average phenotypic traits have increased probability of survival ​ Sickle cell anemia ○​ About.27% of americans of african ancestry have SCA = 100,000 individuals at any one time ○​ About 8.3% are herterozygotes ○​ Frequency of S allele is 20 - 30 times greater in some parts of western and central african populations than in the US ○​ High frequency of S allele is proportional to highfrequnecy of S allele ○​ Conclusion: bothAA and AS are both better adapted than SS individuals in every environment but AS are better adapted in an environment with endemic falciparium malaria= balanced polymorphism ○​ Hunter and gatherers propr to 1500-2000 before present: small populations, mobile -> minimal if any malaria until ​ Bantu horticulterists: -sedentary - large population size. -Cassava and yam farming -using iron tools - Slash and burn -abandoned field -thatched roofs ○​ Genotype involved in producing Hb: ​ AA= normal produced ​ AS= sickle cell trait (carriers, less likely to hospitilized) ​ SS- sickle cell anemia ​ ○​ Plasmodium falciparium ○​ Life cycle involves humans and anopheles mosquitos ○​ Etiology of SCA: ​ Mosquito bites human in correct phase of parasite life cycle ->  ​ Blood stream -> ​ Liver -> ​ Blood -> ​ Red blood cells where uncontrolled reproduction takes place ​ Bursts RBC ​ Transfered back to mosquitos ○​ Found primarily in people of west african descent ​ Effects of low oxygen pressure on hb/rbc: decreased ability to load oxygen at the lungs and decreased amount of oxygen which is released to tissues. Descrsed lifenspan. Decreased* ​ Change in1 out of 438 bases-> change in 1 out of 146 amino acids in beta chain of hemoglobin ​ Codominance ​ Suppose there are two alleles ( A and s) at a locus ○​ Disruptive ​ Monogenic trait: both homozygotes are fitter than the heterozygotes ​ Polygenic trait: Extremes fitter than the middle value ​ enviroment as a result of their supeoror biological design ○​ Higher chance of survival ○​ Higher chance of reproducing then the less well adapted ○​ Greater representation in the next generation. ○​ Fitness ​ Number of offspring that survive to reproductive age ​ Fitness vs adaptedness  ​ ​ Drift ​ Influenced by: lower population size -> greater dirft and vice versa. Greater frequency of neutral mutation -> greater drift ​ Intergenerational drift= offspring gene pool differs from parental gene flow as a result of sampling error in the formation of zygotes ​ Effective population size = individuals actually involved in producing the next generation; about 40% of hunting and gathering bands. ​ Greater varation in reproduction -> greater effect of intergenerational drift ​ Founders effect: ​ Fissioning ​ If the founding population is not representative of the original population -> founders effect possible if restricted gene flow ​ Amish and ellis van creveld syndrome ○​ Gene carried by samuel king or his wife, who migrated to PA in 1774 ​ Pingelap Atoll ○​ Typhon in 1775 killed all but 30 indivudals ○​ Initial population of about 1000 ○​ One survior was a color blind chief ○​ Chiefs have more wives -> more offspring ○​ 5% of the population are now color blind ​ If drift is the only force operating -> fixation ​ Affects of drift: ○​ Greater genetic differences between breeding populations ○​ Less genetic variation with breeding population ​ Evolution has occurred in the last 10,000 years ​ Lactose digestion ​ Inuit and cold ​ Sickle cell and malaria ​ High altitude ​ Skin color and ultraviolet radiation ​ Variation in average body size ​ Genetic resistance to HIV ​ bottleneck effect: ​ Population size reduced by a disaster ○​ Microevolution: evolution over a period of time we can observe. AKA, large scale genetic changes, including extinction and speciation, over relatively long periods of time ​ Primary goal: reconstruction of phylogenies ​ Fossil record  ​ Biological similarities and differences of living species ​ Assumption: species which are biologically simikar because they have a recent common ancestor ​ Parallel evolution: two species have s distant common ancestor by they continue to evolve in a similar manner because they are exposed to similar environmental stress -> natural selection produces similar solutions ​ Convergent evolution: two spedies have a very distant common ancestor byt eventually occupy similar environments -> become more alike over time due to natural selection producing similar solutions ​ Ernst mayr (1942): biological species= group of organisms which can produce fertile and viable offspring ( reproductively isolated) ​ Female horse + male donkey = mule (sterile) but hybrid vigor ​ Leopard frog ○​ Coast of U.S from new england to texas ○​ Any two adjacent groups are phenotypically similar but the phenotypic differences increases with distance ○​ Greater the difference the greater the mortality; no survivors in matings between two geographic extremes ​ Hybridization ○​ 25% of plant species and 10% of animal species have been affected by hybridization ○​ Olive and hamydras baboons, ethiopia ○​ Reproductive isolation is generally adequate definition but there are exceptions ​ Population genetics ​ Synthetic theory of evolution ​ Hardy-Weinberg Theorem ○​ Macroevolution: evolution over a long period of time we can not observe ○​ Ge(4pi^2/GM)rne pool ○​ Suppose population= 50 AA and 50 BO at ABO locus ​ Total alles= ? 200 ​ A alles = 50 * 2 = 100/ 200 = 0.5 alle frequency ​ B alles = 50 * 1= 50/200=0.25 alle frequency ​ O alele = 50 * 1= 50/200=0.25 alle frequency ○​ Breeding population ​ Primary unit of evolution