ANTH120 1nd Edition Week 3 LecturesOutline of Last Lecture I. Notions of Earth's TimelineII. The Problem of FossilsIII. CatastrophismIV. LamarckismV. Darwin's VoyageVI. After the VoyageVII. Natural SelectionOutline of Current Lecture I. Darwin's ColleaguesII. 1859: The Origin of Species and The Unknown MechanismIII. The Principles of HeredityIV. Mendel's ExperimentsV. Mendelian Autosomal TraitsVI. Mendelian Sex-Linked TraitsCurrent Lecture 1. Darwin's Colleagues a) Charles Lyell, Darwin's geologist.- After discovering stone tools in France, he wrote “The Antiquity of Man” in 1863 which presented support for the hypothesis of prehistoric human existence. b) T.H. Huxley, Darwin's Bulldog.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Huxley, initially low-class, worked with way up to the position of renowned scientist and professor after serving as a surgeon on board the HMS Rattlesnake from 1846-50. Like Darwin, he collected specimens and encountered environmental diversity. - He used comparative anatomy to support the hypothesis of the reptilian ancestryof birds, to show that the connection between human and apes is closer than that of humans and monkeys, and to confirm the first example of an extinct human.- After being shown evidence for the process of natural selection, he became a vociferous defender of Darwin's theory. c) Alfred Wallace, Darwin's like-minded colleague.- Wallace created the field of biogeography and independently identified the mechanism of natural selection around the same time as Darwin; he sent Darwina short draft of a paper about it in 1858.- They co-presented the concept at a meeting of the Linnaean Society and Darwin was pressured to publish, despite his desire to amass more supporting evidence. 2. 1859: The Origin of Species and the Unknown Mechanism a) Full title: “On the Origin of Species by Means of Natural Selection: or the Preservation of Favored Races [species] in the Struggle for Life”. It contained 15 chapters and over 500 pages, and ran through 7 printings/editions just during Darwin's lifetime. b) Popular at first, but some objections and misinterpretations:- The public started to worry about the implied connection between humans and apes. Social order was seen to be dependent on the perception of humans as non-animals.- “Social Darwinism” emerged as the notion that poor people are inherently inferior than the elite; the phrase “survival of the fittest” also came from this theory.2- At the time there was no significant organized objections from religious institutions or Americans. c) Mixed reactions from scientists and academics: most still preferred Lamarckism. Many asked, “What exactly is the source of population variation and how is it maintained?” - No one knew about genes and heredity, and asked why unfavored traits remained in next generations. The prevailing theory was Blending Inheritance: - 100% of each parent's genetic material combines in their offspring- This would result in loss of variation very quickly- Darwin, conducting experiments on pea plants, questioned this theory but couldn't analyze his results properly- Darwin died in 1882 after setting in place the theory of evolution by means of natural selection, but with this question of population variation left unanswered. d) Gregor Mendel was working on these questions at the time, but his work wasn't discovered until 1900. 3. The Principles of Heredity a) Modern genetics has two branches: Classical or Mendelian Genetics, which focus on the patterns and processes of inheritance; and molecular genetics, which study DNA properties and functions. We'll focus on Mendelian heredity.- Mendel studied how genes are inherited and how they determine traits.- He showed how population variation is maintained and founded the principles ofheredity.- He studied simple traits: controlled by a single gene, are discrete (either present or absent), and are not affected by environment. - As opposed to complex traits: involve multiple genes, have a range of expression,and are susceptible to environment. b) A trait is a characteristic with alternate phenotypes, and a phenotype is the physical expression of a trait variant.- A dominant phenotype is more common- A recessive phenotype is less common c) Every Mendelian trait phenotype expresses a specific genotype, which is the allelic pair for the same gene.- The two alleles that form the genotype are the allelic pair.- An allele can be dominant or recessive. - A dominant allele will cause expression of the dominant phenotype regardless of its pair.- A recessive allele can only cause expression of the recessive phenotype IF it'spaired with another recessive allele d) Dominant alleles are noted with upper-case letters, and recessive with lower-case (A or a, respectively).- Homozygous dominant genotype, with two dominant alleles, is written as AA. It will express the dominant phenotype.- Homozygous recessive genotype, with two recessive alleles, is written as aa. It will express the recessive phenotype.- Heterozygous genotype, with one of each kind of allele, is written as Aa. It will also express the dominant phenotype. 4. Mendel's Experiments (Note: refer to slides of Punnett squares posted to course website for more detail) a) Gregor Mendel, with a background in botany and statistics, studied the transference of traits across generations of pea plants from 1856-1866.- He chose the pea plant because it's easy to grow, easy to control pollination, easyto create pure lines, and reproduces in large numbers.- He identified seven common traits, each with two phenotypes. These traits—seed and flower color, stem length, etc—are Mendelian (simple). Seeds are either yellow or green; there is no range of expression.4b) The Process: He created a pure line for each yellow and green seeds, so that they would produce only yellow or only green seeds respectively. Then he crossed them to create the first generation of hybrids.- Each plant had yellow seeds! - This is because yellow is the dominant phenotype. Since all the hybrids are heterozygous dominant, they all express the trait of yellow seeds.- Note that this disputes the theory of blending inheritance; there were no yellow-green seeds.- Next, he crossed the first generation of hybrids with each other to