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Anthropology 2E03 Final Exam Review.doc

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Tracy Prowse

Anthropology 2E03 Final Exam Review Information since the midterm Human Variation and Disease  ABO Blood Groups Blood type  “genotypic” trait because the genetic basis is known Unlike “phenotypic” traits, there is no complex interaction between genetic and environmental influences Blood types are useful for understanding population affinities (A similarity of characteristics suggesting a relationship, esp. a resemblance in structure between animals, plants, or languages) and possible examples of natural selection at work. • A gene on Chromosome # 9 codes for antigens, which are proteins on red blood cells • This gene has three alleles or variants  A, B and O • A&B (both A&B are dominant or co-dominant)  are two versions of the antigen •  which is recessive, is the absence of A or B antigen Genotype (6) Phenotype (4) AA Type A Homozygous BB Type B OO Type O AO Type A Heterozygous BO Type B AB Type AB • Blood types were identified in 1909 by Karl Landsteiner Antigen  a substance (usually foreign to a body) attaches to red blood cells. It is capable of causing the production of antibodies (An antigen is a substance that induces the formation of antibodies because it is recognized by the threat in the immune system) Antibody  proteins in blood plasma that react to a foreign substance entering the body (eg. Viruses, bacteria, other persons blood cells) • People who possess type AB blood are known as a Universal Recipient as they can receive blood from anyone • People who posses type O blood are known as Universal Donors. They have no antigens on their blood cells, so the blood cells would not trigger an immune response in another person’s body. They can give their blood to anyone A allele- (21% of the population) B allele- (Rarest – 16% of the population) O allele- (recessive -63% of the population) Why does variability exist in blood types? Haldance (1949) suggested natural selection, specifically disease selection • Most of the evidence though comes from infectious disease • Some microbes may have antigens similar in structure to A, B and O antigens • Immune system may not recognize as invading organisms Cholera People with type O blood are at a greater risk There is a low prevalence of type O blood in areas where cholera is endemic (India) Syphilis Tertiary syphilis more common among people with A, B and AB blood types High % of type O blood among Native Americans may be related to natural selection of treponemal diseases The Plague Increased risk of infection among type O individuals –relatively low % of this blood type in parts of Europe and Asia Plague antigen not “recognized” as foreign by immune system Smallpox More severe scarring among A and AB blood types Summary • ABO blood groups show a clinal distribution • Distributions do not correspond with traditional “racial” categories based on traits like skin colour • Possible selective factors (eg. Infectious disease) may partially explain distribution of blood groups Variation in Human Growth Three Growth Stages 1. Infancy 2. Childhood 3. Adolescence Growth Studies Cross-sectional studies – take measurements on individuals of difference ages and plot data Longitudinal studies (more difficult) – follow the same individuals over a longer period of time What factors influence Growth and Development? 1.) Genetics • Polygenetic • 10 newly identified and 2 previously reported loci strongly associate with variation in height Studies of twins help to assess genetic vs. environmental contributions 2.) Hormones • 2 hormones are important in growth • growth hormone (pituitary gland) • too much GH during growth = gigantism • too little GH = dwarfism • insulin-like growth factors Secular trend  a population change in a biological characteristic that occurs over a period of time, often over generations Explanations for secular increase in stature • Largely environmental • Reduced infectious disease – better health • Better nutrition • Gene flow Summary • Growth is genetically and hormonally controlled, but the expression of growth will vary depending on the individual or community’s environment • Environmental determinants: access to good food and disease load affect growth • Though there are population differences, we have seen a good deal of change in attained growth of populations over the last 500 years • Secular trends in growth indicate that growth responds to changes in the environment Variation in Human Growth Continued… Measuring child growth: malnutrition Prevalence of malnutrition – large surveys Height and weight measurements Sometimes arm circumference and skinfold fat measurements Quickest, least expensive, least invasive Malnutrition  Any kind of poor nutrition, including too much and too little food, or an improper balance of nutrients Children’s growth impacts every stage of their life course • Critical period of growth is during childhood (between the birth and age 5) • Rapid growth • Susceptible to illness, particularly infectious diseases • Depend on adults for nourishment Measuring malnutrition in Modern Populations Sever or acute: “wasting” – low weight-for height (child looks very thin) This index is independent of age Chronic: “stunting: - may be appropriate weight for age, but low height-for-age (i.e. not growing to optimal height) 1.) Environmental Factors: Food/Diet Developing countries - Breastfeeding: - provides nutrients for rapidly growing infants - protects against unclean water - provides baby with extra immunity -Weaning foods: -Must be high in protein and micronutrients (eg. Iron, vitamins, etc) -Many weaning foods are grain based and provide neither 2.) Disease Biggest impact on growth during childhood Synergy (the interaction of elements that when combined produce a total effect that is greater than the sum of the individual elements) between disease and malnutrition Gastro-intestinal diseases - Hinders body’s ability to use nutrients – malabsorption of nutrients - Makes it difficult for children to eat – anorexia - Energy directed to healing the body instead of growing 3.) Built Environment: water and sanitation Water and food borne diseases can precipitate malnutrition Diarrheal diseases and intestinal parasites can stop children from absorbing nutrients or even make them lose their appetite 4.) SES (Socioeconomic status) – income, education, occupation (urban vs. rural) 5.) Toxins and Pollutants - Lead- disrupts bone growth - Cigarette smoke – nicotine and carbon monoxide 6.) Impact of High altitude on growth? - hypoxia – low oxygen availability - lower birth weights - But! Tibetan populations have larger placenta to compensate - possible link to slower postnatal growth rates, but difficult to differentiate high altitude “Small but Healthy Hypothesis” - First proposed by Seckler (1980) - Children who are stunted but not wasted should not be considered malnutrition - Children should be considered in their own ecological context - Through growth and development children are adapting. Critique of small but healthy hypothesis - No evidence that slow and lower growth is without costs Detrimental effects of growth retardation: - Women have smaller pelvis, increase maternal mortality - Cognitive impairment - Lower work capacity - Higher rates of infectious disease Summary • Pattern of human growth is unique • Growth and development can be affected by a variety of internal / external factors • Environment has a profound effect on growth • “Small but healthy” idea interesting but not supported by the evidence Life Span, Aging and Senescence Senescence  Process of growing old, including decline in function Biocultural Approach • Topic is well suited to this approach, as biological results of senescence don’t always match our social cultural approaches to aging Senescence: Biological Consequences, Cellular Level: • Limit to the number of times cell can undergo mitosis – “Hayflick limit” • Chemical changes in membrane and cytoskeleton • Mitochondria less efficient at producing energy • Lower efficiency of lysosomes (garbage collectors) Senescence: Biological Consequences, Organism Level: • Musculoskeletal system – sarcopenia • Skeletal system – resorption of bone outspaces creation – leads to osteopenia and sometimes osteoporosis • Immune system – impaired = infectious disease and cancer • Cardiovascular system – apoptosis of heart muscle cells and atherosclorsis (plaque growth on blood vessels), increase in inflammatory process • Neurological system – grey and white matter declines, lower blood supply to some areas of the brain • Reproductive system – menopause (females) and andropause (males) 10 – 20% decrease in active melanocytes in skin, including hair follicles = grey Follicles decrease and get smaller = thinning hair Skin less elastic, slower growth of cartilage in ears and nose – changes in their form Theories of Senescence Senescence has been positively selected for; genetic component to senescence 1.) Mutation accumulation – mutations with negative effects that happen later in life will not be selected against – senescence result of many genes – polygenic 2.) Antagonistic pleiotropy – one gene having multiple effects, good at young age, bad in old age 3.) Disposable soma – maintaining and repairing body costly, takes energy away from reproduction – trade-off The Grandmother Hypothesis • Humans are born helpless – if mothers mother helps to care for infants/children, mom can forage for food and have more babies faster • Increase in survival of offspring due to grandmothers Summary • Grandmothers help increase survival for offspring • There is a limit to the number of times a cell can reproduce (Hayflick Limit) • Senescence is the process of growing old Human variation and the Environment Human variation is the result of a variety of factors Evolutionary factors – genetic drift, gene flow. Cultural factors – behaviour, learning, exchange of information Phenotypic Plasticity  the ability to develop a variety of phenotypic states under different environmental conditions Growth Plasticity • Stunting and wasting – body’s ability to preserve brain growth at expense of body growth • “Catch-up-growth” – body’s ability during the growth period to accelerate growth to compensate for period of low food resources or environmental stressors such as infectious disease Adaptation  A structure, function or behaviours of an organism that helps it survive and reproduce Types of Adaptations Acclimatization – Physiological response of an Individual organism to changes in the environment (Temporary/reversible) Developmental adaptation – occurs during growth and development – individual level Genetic adaptations – genetic adaptation associated with evolutionary change – Population level Cultural adaptations- learned adaptations to the environment passed from generation to generation – Population level Homeostasis  the ability of an organism to maintain a stable internal environment (temperature, blood pressure) 4 process of Heat Exchange • Radiation (60%) • Conduction (3%) • Convection (15%) • Evaporation (22%) Bergmann’s Rule (body mass and volume) • In mammals, body size tends to be greater in populations that live in colder climates Lower surface area to volume ratio = less heat loss Allen’s Rule (body shape, especially appendages) • In colder climates, shorter limbs are adaptive because they are more effective at preventing heat loss Evolution of Human Heat Regulation • Thermoregulation throug
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