Introduction to Biological Anthropology
Introduction to Biological Anthropology
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Date Created: 04/15/14
ANTH 270 Lecture Three Modern Synthesis and Population Genetics 1 The Modern Synthesis a Merging of natural selection with genetics b 19305 c Dobzhansky Mayr Simpson d The Selfish Gene i Evolution is a change in gene frequency Successful genes are those that replicate themselves the most p i Individuals are just tools genes use to spread themselves 2 Forces of Evolution a Gene Flow i Movement of individuals between populations 3C Moves the alleles carried by the individuals p d Can change allele frequency in both populations iv Can be a chance event unrelated to genotype v Can tend to keep all allele frequencies similar vi Can also spread new alleles that arise in one population vii Migration viii Sex to spread genes ix Species are populations of organisms that cannot or do not interbreed b Genetic Drift i A chance event can cause a change in allele frequency 1 ie A chance event can cause massive death O Survival may be totally unrelated to genotype 1 Contradicts survival of the fittest iv Can have major impacts 1 Bottleneck Effect a Significant part of population dies no reproduction b More likely to experience genetic drift v Founder Effect 1 Loss of genetic variation due to small number of individuals from larger population Mayr 1952 3 Evolution a Microevolution i Change in allele frequency between generations R Hardy Xeinberg Theorem 1 Describes how genotype frequencies in a population relate to allele frequencies in the absence of evolution 2 Assumptions of H W Model Very large population size no genetic drift a b No migration no net mutations no natural selection 0 Random mating P Signi cance i Provides link between Mendelian genetics and evolution 3 Hardy Weinberg Equilibrium a If trait is controlled by two alleles Aa then Ap aq b p22pqq Z31 c This gives frequency of three possible genotypes i AA2Aaaa1 d If observed frequencies are not significantly different from those expected the population is in equilibrium b Macroevolution i Long period of time Q Speciation 1 Species a Distinguished by behavior and morphology b Produce VIABLE offspring 2 Phylogenies a Phenetic explanation i based on existing phenotypic traits b Cladistic explanation i more concerned with genotypes r0 attempts to trace common ancestry 1 Homologous and Analogous traits 0 How do populations evolve 1 Pre mating isolating mechanisms a Geographic barriers or niche partitioning b Reproductive barriers i Morphological differences Behavioral differences 4 Population Genetics Adaptation and Variation a Speciation and extinction i Combination of mutation gene ow genetic drift and natural selection can create new species out of a population in breeding isolation b Speciation i Cladogenesis 1 Splitting or branching of existing species a Allopatric Speciation i Speciation among populations living in two different ranges or territories Geographic isolation leads to reproductive isolation b Sympatric Speciation i Species living in the same or overlapping ranges adapt to different ecological niches p Anagenesis Phyletic transformation 1 Change in allele frequency in entire population without splitting 2 Continuous evolution of an entire species into a descendent species that is phenotypically different 3 Usually a slow accumulation of changes through natural selection gradualism 4 New species simply a matter of enough genetic alteration from original No increase in species diversity 6 Can be difficult to distinguish from EXTINCTION a Loss of entire species no transformation 5 Limits to the Biological Species Concept a Fossils i Unclear how reproductive isolation is defined in fossil record De nes species as gene pool not observable in fossil record b Morphological Species Concept i Morphological characteristics shared between individuals indicate interbreeding 1 Species are polytypic and concept does not account for variability 2 Sibling species differ reproductively but not morphologically 3 SeX dimorphism Life stages a Two groups must be temporally and spatially proximate c Evolutionary Species Concept i A species is a series of ancestor descendent populations passing through time and space independent of other populations each of which possesses its own evolutionary tendencies and historical fate PbC Gap in fossil record create arbitrary distinctions 6 Epigenetics a Human Genome Project 2003 i Discovery of the epigenome 1 Controls the way genes are expressed by controlling access 2 Methyl blocks 3 Acetyl initiates transcription b Methylation and acetylation are driven by cell signals linked to the environment c Epigenetics and Inheritance i Epigenetic tags Reprogramming 1 Erases most epigenetic tags so that the fertilized egg can develop into any type of cell d Summary i Experiences of parents may pass to offspring smoking P Epigenome is more flexible Observing epigenetics is not easy iv When it does occur change happens much more rapidly ANTH 270 Chapter Five Vocabulary 1 10 11 12 13 14 15 16 17 18 Classification In biology the ordering of organisms into categories such as orders families and genera to show evolutionary relationships Chordata The phylum of the animal kingdom that includes vertebrates Vertebrates Animals with segmented body spinal columns these include shes amphibians reptiles including birds and mammals Homologies Similarities between organisms based on descent from a common ancestor Analogies Similarities between organisms based strictly on common function with no assumed common evolutionary descent Homoplasy homo meaning quotsamequot and plasy meaning quotgrowthquot The separate evolutionary development of similar characteristics in different groups of organisms Evolutionary Systematics A traditional approach to classification and evolutionary interpretation in which presumed ancestors and descendants are traced in time by analysis of homologous characters Cladistics An approach to classification that attempts to make rigorous evolutionary interpretations based solely on analysis of certain types of homologous characters those considered to be derived characters Ancestral Referring to characters inherited by a group of organisms from a remote ancestor and thus not diagnostic of groups lineages that diverged after the character first appeared also called primitive Clade A group of organisms sharing a common ancestor The group includes the common ancestor and all descendants Monophyletic Referring to an evolutionary group clade composed of descendants all sharing a common ancestor Polyphyletic Referring to an evolutionary group composed of descendants with more than one common ancestor and thus not a true clade Derived modified Referring to characters that are modified from the ancestral condition and thus diagnostic of particular evolutionary lineages Theropods Small to medium sized ground living dinosaurs dated to approximately 150 mya and thought to be related to birds Shared Derived Relating to specific character traits shared in common between two life forms and considered the most useful for making evolutionary interpretations Phylogenetic Tree A chart showing evolutionary relationships as determined by evolutionary systematics It contains a time component and implies ancestor descendant relationships Cladogram A chart showing evolutionary relationships as determined by cladistic analysis It39s based solely on interpretation or shared derived characters It contains no time component and does not imply ancestor descendant relationships Biological Species Concept A depiction of species as groups of individuals capable of 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 fertile interbreeding but reproductively isolated from other such groups Speciation The process by which a new species evolves from an earlier species Speciation is the most basic process in macroevolution Recognition Species Concept A depiction of species in which the key aspect is the ability of individuals to identify members of their own species for purposes of mating and to avoid mating with members of other species In theory this type of selective mating is a component of a species concept emphasizing mating and is therefore compatible with the biological species concept Ecological Species Concept The concept that a species is a group of organisms exploiting a single niche This view emphasizes the role of natural selection in separating species from one another Ecological Niche The position of a species within its physical and biological environments A species39 ecological niche is defined by such components as diet terrain vegetation type of predators relationships with other species and activity patterns and each niche is unique to a given species Together ecological niches make up an ecosystem Sexual Dimorphism Differences in physical characteristics between males and females of the same species For example humans are slightly sexually dimorphic for body size with males being taller on average than females of the same population Sexual dimorphism is very pronounced in many species such as gorillas Intraspecific Within species refers to variation seen within the same species Interspecific Between species refers to variation beyond that seen within the same species to include additional aspects seen between two different species Paleospecies Species defined from fossil evidence often covering a long time span Genus A group of closely related species Fossils Traces or remnants of organisms found in geological beds on the earth39s surface Mineralization The process in which parts of animals or some plants become transformed into stone like structures Mineralization usually occurs very slowly as water carrying minerals such as silica or iron seeps into the tiny spaces within a bone In some cases the original minerals within the bone or tooth can be completely replaced molecule by molecule with other minerals Taphonomy The study of how bones and other materials come to be buried in the earth and preserved as fossils Geological Time Scale The organization of earth history into eras periods and epochs commonly used by geologists and paleoanthropologists Continental Drift The movement of continents on sliding plates of the earth39s surface As a result the positions of large landmasses have shifted drastically during the earth39s history Epochs Categories of the geological time scale subdivisions of periods In the Cenozoic era epochs include the Paleocene Eocene Oligocene Miocene and Pliocene from the Tertiary Period and the Pleistocene and Holocene from the Quaternary Period 34 35 36 37 38 Neocortex The more recently evolved portions of the corteX of the brain that are involved with higher mental function and composed of areas that integrate incoming information from different sensory organs Placental A type subclass of mammal During the Cenozoic placentals became the most widespread and numerous mammals and today are represented by upward of 20 orders including the primates Heterodont Having different kinds of teeth characteristic of mammals whose teeth consist of incisors canines premolars and molars Endothermic Able to maintain internal body temperature by producing energy through metabolic processes within cells characteristic of mammals birds and perhaps some dinosaurs Adaptive Radiation The relatively rapid expansion and diversification of life forms into new ecological niches
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