10/4/20171Course Business• Midterm 1– Tuesday, 10/10• Material covered on the midterm:– Lectures: weeks 1-5– Labs: 1-4– Textbook: ch. 1-4 & 14• 50 objective questions– Multiple choice– True/false– Matching• Study guide will be posted this week210/4/20172Creating Evolutionary or Phylogenetic Trees3ConvergenceAncestralShared DerivedDerivedWarm-bloodedLoss of premolarLoss of tail• Warm-blooded: yes yes yes yes• Hair color: tan grey black orange• Premolar #: 3 2 2 2• Tail: yes yes no no4Full orbital convergence10/4/20173Cladistics• Primitive or Ancestral characters, even though homologous, do not help in sorting relationships• Unique characters do not help in sorting relationships• Only SHARED, DERIVED characters can sort relationships within a group5Darwin’s 5 theories regarding evolution1. Species change [evolution as such]2. All organisms share a common ancestry3. Evolution is gradual4. Evolution leads to speciation5. Evolution occurs through Natural Selection610/4/20174Darwin’s Radical IdeaComplexity of organisms and ecosystems are merely byproducts of individual animals struggling to optimize their reproductive success in their local environment.78This can be a HORRIFICALLY dangerous idea if you commit the following fallacies:10/4/20175Most Frequent Problem #1:the Fallacy of Evolution as Progress910African Elephant vs. Pleistocene Eurasian Mammoth10/4/20176Problem #2: Why is Natural Selection not about the “Survival of the Fittest”?11Herbert Spencer (1820-1903)Spencer’s arguments on society mirroring biology led to the theory of “Social Darwinism,” which had nothing to do with Darwin’s arguments at all.1210/4/20177Social Darwinism13The belief that helping the poor and sick would get in the way of evolution, which depends on the survival of the fittest, led in the 1920s directly to Eugenics (artificial selection on human populations as governmental policy) in the US, Britain, Sweden, and Germany, leading eventually to Nazi Germany’s “Final Solution” to murder 11 million people in poison gas chambers and machine gun executions.“Let us understand, once and for all, that ethical progress of society depends not on imitating the cosmic process [of natural selection], still less running away from it, but in combating it.” Thomas H. Huxley1410/4/20178Problem #3: The Naturalistic Fallacy =the idea that what is natural is morally justifiable, and the inverse.15Our Natural Habitat or an Alien Environment?1610/4/2017917Natural UnnaturalGoodBadNature ≠ MoralityNature ≠ MoralityNatural UnnaturalGoodBabiesKnowledgeLoveNovelsHealth care Craft specializationBadEpidemicsFamineExtinctionsParasitismHuman slaveryPollutionNuclear weapons1810/4/201710The Consequences of Darwin’s Radical Idea:We have the choice to apply whatever system of morality we wish (the ultimate “free will”).19ALA#5: Jefferson’s Blood• A demonstration of the mutability of “race” and the confusion of cultural behavior, biological traits, and misunderstandings of variation.2010/4/201711212210/4/201712232410/4/20171325ALA #5: Take-home Assignment on Jefferson’s Blood• Within one page of single-spaced text (12-point font), discuss the issues facing Amelia Cooper after her discovery that she is a descendent of Thomas Jefferson and his slave Sally Hemings. How do these issues relate to biological descent, biological phenotypic variability, & cultural variables of identity & community?• Turn in at lecture on Tuesday (10/17/17).2610/4/20171427Population GeneticsTasks for Today• How population genetics can identify Natural Selection in action:– Balanced Polymorphisms (ex: sickle cell anemia)• Modern human variation: human adaptation to local climate:• skin color, • body form, • high altitude norm of reaction vs. adaptation, • lactose tolerance2810/4/201715Sickle Cell Anemia• Hemoglobin is coded for by the allele HbA• Some individuals have a variant, HbS, which is seriously deleterious in the homozygous state (life expectancy only 45 years)• Heterozygotes are carriers and healthy under normal conditions– Sickling only occurs under severe levels of low oxygen (i.e., severe athletics)29Sickle cell anemia caused by point mutation30Uracil baseAdenine base, not thymineValine amino acid10/4/20171631Consequences of sickle alleleWe might expect that this allele would be eliminated because of its lethal effects. Yet in some populations the allele frequency reaches 5% - 20%?Why?3210/4/2017173334Mosquitoes: the vector for Plasmodium, the protozoan parasite that causes falciparum malaria© London School of Hygiene/Photo Researchers, Inc.10/4/201718Sickle allele as a Balanced Polymorphism• S allele selected for in tropical environments because the heterozygotes have the highest fitness in malarial environments351011121314-3.89E-16 0.05 0.1 0.15 0.2 0.25 0.3frequency of sickle cell alleledeaths/100Total number of deaths due to malaria & sickle cell anemiaAdapted from Mielke et al. 2006Hemoglobin E Sickling Allele• Another variant is HbE– Also single point mutation• Found in southeast Asia• Homozygotes not selected against as severely as HbS, but there is favored selection in heterozygotes & these areas also have malaria risk 3610/4/201719Any Questions?37Human Skin• Unique features– Largest organ of the body– Lack of visible hair– Sweat glands– Pigmented• Functions– Protection– Regulates body temperature– Detects info about the environment– Plays a role in vitamin D production3810/4/201720Skin Structure• Epidermis– Melanocytes– More melanin produced darker skin• Dermis – Hair follicles– Sweat glands – Blood vessels – Nerves39Human Variation: Skin Color4010/4/20172141Questions…1. Why is darker skin more adaptive at or near the equator?2. Why did skin color become lighter farther away from the equator?3. Is the same explanation responsible for 1 & 2 or did different selective factors operate at different latitudes? 4210/4/201722Problems with too much sun• Sunburn– Severe complications• Skin cancer– Rates decrease away from the equator43Melanin, produced in greater amounts by individuals with darker skin, protects from dangerous effects of UV raysProblems with too much sun• Folate (a B vitamin) degradation– B vitamin essential for DNA synthesis & cell replication– UV radiation exposure causes a breakdown of folate in the bloodstream• Deficiencies in folate
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