Mod. 2 Lectures 5-7
Mod. 2 Lectures 5-7 ASM 104
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This 6 page Class Notes was uploaded by Gabrielle Hsu on Friday September 4, 2015. The Class Notes belongs to ASM 104 at Arizona State University taught by Campisano in Fall 2015. Since its upload, it has received 118 views. For similar materials see Bones, Stones/Human Evolution in anthropology, evolution, sphr at Arizona State University.
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Date Created: 09/04/15
MODULE 2 LECTURE 5 INTRODUCTION This lecture is about population genetics which studies the distribution of allele frequencies percentages in a population MAIN IDEAS Equilibrium allele amp genotype frequencies stay constant throughout generations Requirements for a population to reach equilibrium Very large population small populations are too strongly affected by genetic drift Completely random mating all individuals are able to mate amp all produce the same number of offspring No mutation No gene ow between populations No natural selection no alleles have an advantage or disadvantage HardyWeinberg principle equilibrium Hardy was a mathematician amp Weinberg was a physician Developed a principle together which states that evolution would not occur frequencies of gametes genotypes amp phenotypes would remain constant in the absence of the above factors genetic drift gene ow mutation natural amp sexual selection Formula calculates a population s genotype amp allele frequencies from one generation to the next without evolution 0 p2 2pq q2 1 total population 0 pq1 o p represents one allele variant amp q represents the other p2 and q2 are homozygous genotypes amp pq is heterozygous Example Calculating what percentage of our population has cystic fibrosis CF if we know that 1 in 1700 babies is born with CF F normal dominant f CF recessive FF homozygous dominant no CF Ff heterozygous carrier but doesn t have CF ff homozygous recessive has CF F22Fff2 Ff1 1 f2 11700 00059 or 059 Iff2 059 then f 024 If Ff 1thenF976 F2 9762 953 or 953 Ff 976 x 024 0468 or 468 953 X 1700 16201 0468 x 1700 7956 So 16201 people or 953 are homozygous normal 7956 people or 468 are carriers and the remainder are homozygous recessive and have CF CONCLUSIONSUMMARY Connection with evolution We would know evolution is occurring if these frequencies changed For example research shows that CF carriers are more resistant to certain other diseases including cholera If cholera occurred very frequently than the heterozygous allele would have an advantage and would become more prevalent similar to what has happened with sicklecell disease Population genetics studies the effects of evolutionary forces like mutation gene ow genetic drift and natural amp sexual selection by observing the distribution and changes over time of alleles MODULE 2 LECTURE 6 INTRODUCTION This lecture is about the role of species in evolution KEY POINTS Important observations about populations species Populations vary discretely corresponding to reproductive boundaries for sexually reproducing organisms Behavioral amp morphological variation is used to identify species but reproductive boundaries have the genetic significance Species closed or exclusive communities of gene exchange Basic foundational units of evolution Most common definition comes from German ornithologist Ernst Mayr Systematics and the Origin of Species 1942 Biological Species Concept Groups of interbreeding natural populations that are reproductively isolated from other such groupsquot MAIN IDEAS Reproductive isolation Premating o Mating does not occur 0 Temporal ecological behavioral amp mechanical factors different mating seasons different habitats physical incompatibility etc Postmating o Mating occurs but with no offspring or offspring unable to reproduce o Gametic incompatibility sperm does not fertilize the ovum o Zygotic mortality zygote does not develop into an embryo 0 Hybrid inviability zygote develops into an embryo but the fetus doesn t survive 0 Hybrid sterility fetus survives but once born cannot reproduce Typological species concept Linnaeus preDarwin creationist Swedish naturalist Species are as many as were created in the beginning by the Infinitequot Species were viewed as static amp unchanging made as God intended Does not allow for evolution Biological species concept Definition of a species relates to whether or not they have distinct breeding communities not their physical and behavioral qualities Speciation Allopatric speciation most common type Two populations that were connected by gene ow become isolated often by a physical barrier like a mountain range or body of water Gene ow stops Natural selection amp genetic drift lead to genetic differences between the populations If they met individuals from the different populations would no longer recognize each other as mates or could not produce fertile offspring Peripatric speciation Smaller population of a species becomes isolated Founder effect often on the margins of the species range where resources are scarce or habitat is otherwise unstable Forces such as genetic drift produce rapid changes in the smaller population while the original remains unchanged Smaller population becomes reproductively isolated from the original one SUMMARY Speciation requires geographic isolation This stops gene ow between populations allowing for rapid changes due to genetic drift amp natural selection Changes in reproduction including mate recognition result in isolation from the original population Cladogenesis permanent division of the original species into two distinct species Speciation gt biodiversity MODULE 2 LECTURE 7 INTRODUCTION This lecture is about systematics or the science of relationships among organisms KEY POINTS In systematics organisms are grouped by descent from common ancestors Linnaeus Systema Naturae grouped organisms into Kingdom Phylum Class Order Family Genus amp Species Charles Darwin later documented the idea of a tree of lifequot with species branching off from common ancestors MAIN IDEAS Phylogeny Treelike diagram depicting relationships between species including branching from common ancestors Constructed using heritable characteristics that vary between species Morphological chromosomal molecular or behavioral Homologies characteristics shared between species that were inherited from a common ancestor Homoplasies characteristics shared between species that are not related to common ancestry but evolved independently Cladogram branching diagram similar to a phylogeny except ancestors are hypothetical rather than specific extinct species and the time scale is relative instead of absolute Essentially a more basic version of a phylogeny with less information Convergence species have different ancestors but similar environmental pressures cause them to develop similar features through natural selection This produces homoplasy Types of homologies Derived evolved in a group of species most recent common ancestor Ancestral evolved in more distant common ancestors The polarity of a characteristic states whether it is derived or ancestral Symplesiomorphy sharedancestral characteristic a characteristic shared by a group of species that is not unique only to those species Example humans and apes both have spines but so do all other vertebrates Synapomorphy sharedderived characteristic a characteristic shared by a group of species that IS unique to those species and therefore used as evidence for shared ancestry Outgroup analysis using other species outside of a group of species being studied to determine the polarity of characteristics of the group being studied Example humans amp apes do not have tails We can determine that this is a synapomorphy or a sharedderived characteristic by studying other closely related monkeys and observing that they all have tails All living species of apes amp humans as well as their ancestors are classified as Hominoidea because of this amp many other synapomorphies Monophyly group of species determined to have shared a unique common ancestor based on their synapomorphies CONCLUSION The goal of phylogenetic analysis is to identify monophyletic groups amp study the relationships of the species within those groups
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