Chapter 5 Outline: Evolution and Genetics - Kottak Introduction to Anthropology
Chapter 5 Outline: Evolution and Genetics - Kottak Introduction to Anthropology SOCA 105
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This 5 page Class Notes was uploaded by Shelby Charette on Thursday January 21, 2016. The Class Notes belongs to SOCA 105 at West Virginia University taught by Genesis Snyder in Fall 2015. Since its upload, it has received 274 views.
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Introduction to Anthropology Notes 9/27/2015 Chapter 5: Evolution and Genetics Compared with other animals, humans have uniquely varies ways – cultural and biological – of adapting to environmental stresses. o Exemplifying cultural adaptation, we manipulate our artifacts and behavior in response to environmental conditions… In the 18 century, Carolus Linnaeus developed biological taxonomy. He viewed differences and similarities among organisms as part of God’s orderly plan rather than as evidence for evolution. EVOLUTION o As in other species, human populations adapt genetically in response to environmental forces, and individuals react physiologically to stresses Ex. when we work in midday sun, sweating occurs spontaneously, cooling the skin and reducing the temperature of subsurface blood vessels o According to creationism, biological similarities and differences originated at the Creation Fossils showed that different life had once existed. However, if all life had originated at the same time, why weren’t ancient species still around? Why weren’t contemporary plants and animals found in the fossil records? A modified explanation combining creationism with catastrophism arose to replace the original doctrine… o In this view, fires, floods, and other catastrophes, including the biblical flood involving Noah’s ark, had destroyed ancient species o Theory and Fact The alternative to creationism and catastrophism was transformism, also called evolution Evolution – transformation of species; descent with modification Evolutionists believe that species arise from others through a long and gradual process of transformation, or descent with modification… o ***Charles Darwin*** Uniformitarianism – belief that natural forces @ work today also explain past events The present is the key to the past!!!! ^^^ theory developed by Charles Lyell (father of geology) that influenced Darwin o Charles Darwin provided a theoretical framework for understanding evolution. Offered natural selection as a powerful evolutionary mechanism that could explain the origin of species, biological diversity, and similarities among related life forms Proposed the Theory of Evolution Wrote, The Origin of Species Introduction to Anthropology Notes 9/27/2015 Natural Selection – the process by which the forms most fit to survive and reproduce in a given environment do so in greater numbers than others in the same population Operates when there is competition among members of the population for strategic resources, such as food and space For natural selection to work on a particular population, there must be variety w/n that population as there always is o Theory and Fact Continued… Inheritance of Acquired Characteristics (INCORRECT) o Ex. idea that in each generation, individual giraffes strain their necks to reach just a bit higher and this straining somehow modifies their genetic material British Moths? (Speckled versus Darker Moth) o The darker moth was favored during the industrial revolution b/c the polluted environments and lighter-colored moths o A change in this species illustrates recent natural selection through what has been called industrial melanism GENETICS o Charles Darwin recognized that for natural selectin to operate, there must be variety in the population undergoing selection o Genetics, a science that emerged after Darwin, helps us understand the causes of biological variation… Biochemical changes (mutations) in DNA provide much of the variety of which natural selection operates Mendelian Genetics - studies the ways in which chromosomes transmit genes across the generations Biochemical Genetics – examines structure, function, and changes in DNA o Population Genetics – investigates natural selection and other causes of genetic variation, stability, and change in breeding populations o Mendel’s Experiments Studies heredity and traits in pea plants Through his experiments, he discovered that heredity is determined by discrete particles, or units Dominant versus Recessive Traits Chromosomes Arranged in matching homologous pairs Humans have 46 chromosomes, arranged in 23 pairs, one in each pair from the father and the other comes from the mother Gene Alleles – a variant of a particular gene In Mendel’s experiments, the seven contrasting traits were determined by genes on seven different pairs of chromosomes… Heterozygous – having dissimilar alleles of a given gene Introduction to Anthropology Notes 9/27/2015 Homozygous – having identical alleles of a given gene Dominance produces a distinction b/w genotype and phenotype Genotype – an organism’s hereditary makeup o WHAT YOU REALLY ARE GENETICALLY Phenotype – an organism’s evident biological traits o WHAT YOU APPEAR AS o Independent Assortment and Recombination Independent Assortment – chromosomes inherited independently of one another Recombination is important in biological evolution b/c it creates new types on which natural selection can operate BIOCHEMICAL, OR MOLECULAR, GENETICS o Mutations – changes in DNA molecules of which genes and chromosomes are built DNA can copy itself, form new cells, replace old ones, and produce the sex cells (or gametes) DNA’s chemical structure also guides the body’s production of proteins – enzymes, antigens, antibodies, hormones, and hundreds of others o Cell Division An organism develops from a fertilized egg, or zygote, created by the union of two sex cells(gametes), a sperm from the father and an egg (ovum) from the mother The zygote grows rapidly through mitosis, or ordinary cell division, which continues as the organism grows… Meiosis – process by which sex cells are produced Unlike ordinary cell division, in which two cells emerge from one, in meiosis four cells are produced from one o Crossing Over – homologues chromosomes intertwine and exchange DNA b/c of crossing over, each new chromosome is partially different from either member of the original pair... o Mutation Mutations are the most important source of variety on which natural selection depends and operates The simplest mutation results from substitution of just one base in a triplet by another, called base substitution mutation Chromosomal Rearrangment- pieces of a chromosome can break off, turn around and reattach, or migrate someplace else on that chromosome Can lead to speciation (formation of a new species) POPULATION GENETICS AND MECANISMS OF GENETIC EVOLUTION o Population genetics studies the stable and changing populations in which most breeding normally takes place. Introduction to Anthropology Notes 9/27/2015 o Gene Pool – refers to all alleles, genes, chromosomes, and genotypes w/n a breeding population – the “pool” of genetic material available o Genetic Evolution – change in gene (allele) frequency in a breeding population from generation to generation Any factor that contributes to the change can be considered a mechanism of genetic evolution… These mechanisms include natural selection, mutation, random genetic drift, and gene flow… o Natural Selection Genotype – just hereditary factors – genes and chromosomes Phenotype – the organism’s evident biological characteristics – develops over the years as the organism is influenced by particular environmental forces Includes outward physical appearance, internal organs, tissues and cells, and physiological processes and systems… Human biology is not set @ birth, but has considerable plasticity AKA…it’s changeable!! o Natural Selection Continued… The environment works on the genotype to build the phenotype, and certain phenotypes do better in some environments than others do… a. Directional Selection After several generations of selection, gene frequency will change… adaptation through natural selection will have occurred…once this happens, those traits that have proved to be the most adaptive (favored by natural selection) in that environment will be selected again and again from generation to generation Given such directional selection, or long-term selection of the same trait(s), maladaptive recessive alleles will be removed from the gene pool Directional Selection will STAY THE SAME as long as environmental forces stay the same. ***Natural Selection reduces variety in a population through directional selection – by favoring one trait over the other…*** b. Sexual Selection – selection of traits the enhance mating success Selection also operates through competition for mates in a breeding population c. Stabilizing Selection Selective forces also can work to maintain variety through stabilizing selection, by favoring a balanced polymorphism… Balanced Polymorphism – alleles maintain a constant frequency in a population over time Introduction to Anthropology Notes 9/27/2015 May happen b/c the phenotypes they produce are neutral, or equally favored, or equally opposed by selective forces o Random Genetic Drift – genetic change due to chance Although genetic drift can operate in any population, large or small, fixation due to drift is more rapid in small populations. Fixation refers to the total replacement of blue marbles by red marbles… o Gene Flow – exchange of genetic material through interbreeding Species – population whose members can interbreed to produce offspring that can live and reproduce Speciation – formation of new species THE MODERN SYNTEHSIS o This is what the currently accepted view of evolution is known as… o This refers to the synthesis or combination of Darwin’s theory of evolution by natural selection and Mendel’s genetic discoveries o Microevolution and Macroevolution are two ends of a continuum of evolutionary change in which gradually changing allele frequencies in a population eventually can lead to the formation of new species Microevolution – genetic changes in a population or specs over a few, several, or many generations, but w/o speciation Macroevolution – refers to larger-scale or more significant genetic changes in a population or species, usually over a longer time period o Punctuated Equilibrium – long periods of stability,,, during which species change little, are interrupted with occasional evolutionary leaps
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