Week of Nov 16
Week of Nov 16 Biology201
Popular in Principles of Ecology and Evolution
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This 0 page Class Notes was uploaded by firstname.lastname@example.org Notetaker on Saturday November 21, 2015. The Class Notes belongs to Biology201 at Indiana University of Pennsylvania taught by Dr. Josiah Townsend in Fall 2015. Since its upload, it has received 8 views. For similar materials see Principles of Ecology and Evolution in Biology at Indiana University of Pennsylvania.
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Date Created: 11/21/15
Week of November 16 Lecture 21 Chapter 24 Speciation 1 Speciation a Speciation origin of new species Focal point of evolutionary theory Species kind or appearance b Evolutionary theory must explain how new species originate and how populations evove Microevolution consists of changes in allele frequency in a population over time Macroevolution broad patterns of evolutionary change above the species level a Speciation is what links micro and macro evolution together 2 Biological Species Concept a Biological species concept a species is a group of pops whose members have the potential to interbreed in nature and produce viable fertile offspring Gene flow between pops holds a species together genetically b Reproductive isolation existence of biological factors that impede tow species from producing viable fertie offspring a Hybrids offspring of crosses between different species b Prezygotic barriers block fertilization from occurring by I ii iii iv v vi vii Impeding different species from attempting to mate Preventing the successful completion of mating Habitat isolation two species encounter each other rarely or not at all because they occupy different habitats even though not isolated by physical barriers Temporal isolation species that breed at different times of the day seasons or different years cannot mix their gametes Behavioral isolation courtship rituals and other behaviors unique to a species are effective barriers to mating Mechanical isolation morphological differences can prevent successful completion of mating Gametic isolation sperm of one species may not be able to fertilize the egg of another species b Postzvootic barriers prevent the hybrid zygote from developing into a viable fertile adult Reduced hvbrid viabilitv genes of the different parent species may interact and impair the hybrid39s development or survival in its environment Reduced hybrid fertility being sterile Hybrid breakdown some rst generation hybrids are fertile bu when they mate with each other or either parent species those offspring are sterie 1 Limitations of the Biological Species Concept a Cannot be applied to fossils b Cannot be applied to asexual organisms including all prokaryotes c Emphasizes absence of gene flow d Grolar bear hybrid of grizzly and polar bears 2 Speciation can take place with or without geographic separation a Allopatric speciation other country i Physical boundary that keeps the two species apart ii Genetic drift bottleneck founder effects iii Gene glow is interrupted or reduced when a pop is divided into a geographically isolated subpopulation iv Flightless cormorant of the Galapagos most likely came from a ying species on the mainland a Sympatric speciation same country i Species living together ii lsolate themselves iii Generalization 2 Process of Allopatric Speciation a i A canyon may create a barrier for small rodents but not birds coyotes or pollen b Separated pops may evolve independently through mutation natural selection and genetic drift Byproduct of genetic divergence Most common mode of speciation i Snapping shrimp15 pairs of sister species b Regions with many geographic barriers generally have more species that regions with fewer barriers i Reproductive isolation between pops generally increases as the distance between them increases 2 Sexual Selection a b For mates of different colors has likely contributed to speciation in cichlid sh in Lake Victoria c Habitat differentiation i Sympatric speciation can also result from the appearance of new ecological niches ii North American maggot y that live sin native hawthorn trees and newer apple trees 2 Hybrid zones reveal factors that cause reproductive isolation a Hybrid zone region in which members of different species mate and produce hybrids b Hybrids are the result of mating between species with incomplete reproductive barriers c Three possible outcomes i Reinforcement hybrids aren39t fertile pops maintain separation ii Fusion two species really aren39t so different iii Stability hybrids can occur but never have high numbers 2 Patterns in the Fossil Records 10 a a Punctuated equilibria describes the periods of apparent stasis punctuated by sudden change i Contrasts with a model of gradual change in a species over time Lecture 22 Chapter 26 Building the Tree of Life 1 Investigating the Tree of Life a Legless lizards have evolved independently several times i At least ve families of legless lizard species b Phylogeny evolutionary history of a species or group of related species i Shows that legless lizards and snakes are related b Systematics classi es organisms and determines their evolutionary relationships i Taxonomy classifying and naming organisms ii Linnaeus created binomial naming hierarchical classi cation iii Genus rst part of the name iv Speci c epithet unique for each species within a genus b HierarchicalClassi cation i Domain kingdom phylum class order family genus and species ii Taxon taxonomic unit at any level iii quotboxes within boxesquot iv Tree form 2 Linking Classi cation and Phylogeny a phvlooenetic tree evolutionary history of a group of organisms represented i ii Branch point divergence of two species iii Sister taxa groups that share an immediate common ancestor iv Basal taxon same as ancestor v Polytomy an unresolved pattern of divergence badly designed tree b Difference between classi cation and phylogeny l b Shared characters are used to construct phylogenetic trees i Homologous characters used to infer a phylogeny ii Clade group of species that include an ancestral species and its descendants iii Monophyletic consists of the ancestor species and ALL its descendants iv Paraphyletic consists of an ancestral species and some but not all descendants NOT VALID include most recent common ancestor v Polyphyletic includes distantly related species but does not include most recent common ancestor NOT VALID Phylogenetic Trees with Proportional Branch Lengths a Length of branch can re ect the number of genetic changes that have taken place in a particular DNA sequence in that lineage b OR can represent chronological time c OR branching points can be determined from the fossil record What We Can and Cannot Learn from Trees a Show patterns of descent NOT phenotypic similarity b DO NOT indicate when species evolved or how much change occurred in a Hneage c Should not be assumed that a taxon evolved from the taxon next to it i Both descended from a common ancestor Phylogenies are inferred from morphological and molecular data a Homologies phenotypic and genetic similarities due to shared ancestry b Analogy similarity due to convergent evolution c Convergent evolution occurs when similar environmental pressures and natural selection produce similar adaptations d MEGA6 program used for DNA analyses i Looks for similar DNA sequences ii DNAchangescomparisons Phylogenetic Trees as Hypotheses a Best hypotheses for trees t the most data morphological molecular and fossil a Provide important info about similar characteristics in closely related species i Modern use ii Why are you do something Must be applied to be worth the effort time and money b Endangered Species Forensics tree was used to id the species of whale meat that was being sold to determine whether or not that species is legal to harvest
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