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Introductory Biology

by: Alec Sullivan

Introductory Biology

Marketplace > University of Washington > Biology > Introductory Biology
Alec Sullivan


Kerry-Anne Naish

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Week 1 Notes Hypothesis testing, evidence for evolution, evolution by natural selection, Mendelian genetics.
Kerry-Anne Naish
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This 10 page Reader was uploaded by Alec Sullivan on Sunday April 13, 2014. The Reader belongs to a course at University of Washington taught by a professor in Fall. Since its upload, it has received 170 views.


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Date Created: 04/13/14
331 Hypothesis testing and experimental design Chapter 15 The Nature of Science Science formulating hypotheses and finding evidence to support reject the hypothesis Two ways of testing hypothesis experiments or observational studies Why Do Giraffes Have Long Necks Introduction to Hypothesis Testing 0 quotGiraffes need long necks to compete for food plausible but untested hypothesis o Robert Simmons and Lue Scheepers formed alternate hypothesis long necks are advantageous for fights related to mating o Hypothesis testing I Operationalize a precise hypothesis I List the predictions I Design observationaIexperimental study capable of testing o If hypothesis is not supported I Modify hypothesis I Search for alternative explanations I Review methodology The Food Competition Hypothesis Predictions and Tests o Hypothesis Giraffes compete for food and during food scarcity giraffes w long necks can reach food unavailable to other species o Predictions o Neck length is variable among giraffes confirmed o Neck length is heritable assumed o Giraffes feed in high trees especially during dry season rejected The Sexual Competition Hypothesis Predictions and Tests o Breed year round rather than seasonally o Combat between male giraffes to compete for females o Longer necks allow for harder blows to opposing giraffes needs testing How Do Ants Navigate Introduction to Experimental Design o Experiments test single we defined factor o Research question when ants leave the nest to search for food how do they find their way back The Pedometer Hypothesis o Ants integrate information from leg movements angles distances stride length to determine distance from home o Null hypothesis Stride length and step number should have no effect on the ability of an ant to return to its nest o Null hypothesis what should be observed when hypothesis is wrong Testing the Hypothesis o Ants walk from nest to feeder through a channel 10 meters o Ants are caught and added to one of three groups 25 ants per group o Stumps shorter strides o Normal no change o Stilts longer strides o Ants are sent home in channel o Stumps stopped short stilts stopped long o Retested after few days all walked correct distance Important Characteristics of Good Experimental Design o Include control groups o Experimental control conditions o Example same species same nest same time of day same humiditytemp o Replication large sample sizes Bioskills 3 0 Read axes then data points then overall trends 0 X axis abscissa independent variable the manipulated variable 0 Y axis ordinate dependent variable the responding variable 0 Continuous versus discrete data Types of Graphs Scatterplots Lines Curves o Scatterplots data points maybe connected dotsline of best fit o Smooth line line of best fit o Curved line characteristic shape like be curvesigmoid curve Bar Charts Histograms Box andWhisker Plots o Bar charts discretecategorical values o Histograms frequency data as numbers or percentages o Box andwhisker plots box indicates half of data numbers whiskers are maxmin vertical line in the box indicates median 41 The evidence for evolution Chapter 25 Evolution by Natural Selection 0 Populations of organisms evolve and change overtime 0 Leading theory before 1859 was special creation 0 Theory of Special Creation o All species are independent o Life on Earth is young quot396000 years old o Species are immutable unchangeable 0 Scientific theory has two components pattern and process o Pattern summarizes a series of observations the facts o Process a mechanism that produces the pattern Chapter 251 The Evolution of Evolutionary Thought 0 A scientific evolution overturns an existing idea Plato and Typological Thinking o Species don t change o Variations aren t important Aristotle and the Great Chain of Being o Great chain of beingScale of nature linear scheme of known organisms o Organized based on increased size and complexity Lamarck and the Idea of Evolution as Change through Time o Proposed that species change over time o Pattern based on Great Chain I Simple organisms at base originate spontaneously I Organisms evolve to more complexity I Progressive evolution o Inheritance of acquired characteristics eg giraffe stretches tall has offspring w longer necks Darwin and Wallace and Evolution by Natural Selection o Population individuals of same species living in the same area at the same time o Population thinking variation among individuals in a population o Theory of evolution I Overturned idea that species are static I Replaced typological thinking w population thinking I Proposed a testable mechanism Chapter 252 The Pattern of Evolution Have Species Changed and Are They Related 0 Evolution described as quotdescent with modification 0 Theory of evolution o Pattern I Species change through time I Species related by common ancestry o Process I Natural selection Evidence for Change through Time Fossil any trace of an organism that lived in past eg bones tracks dung Fossil record all fossils found so far in scientific literature Extant species living today not extinct The Vastness of Geological Time I Fossils organized relatively by sedimentary rock formation I Geological time scale indicated Earth was more than 6000 years old I Radiometric dating o Observed decay rates of parent to daughter atoms o Ratio of parent to daughter atoms present in newly formed rocks o Ratio present in a particular rock sample I Earth is about 46 billion years old Extinction Changes the Species Present Over Time I Baron Georges published the idea of extinct species in 1812 using Irish elk example I About 99 of species that ever lived are now extinct Transitional Features Link Older and Younger Species I quotLaw of succession extinct species were succeeded in the same region by similar species I Transitional feature trait in a fossil species that is intermediate between ancestral and derived species Vestigial Traits Are Evidence of Change Through Time I Vestigial trait reduced or incomplete structure that has reducedno function I Examples o Whalessnakes have tiny hipleg bones I do not aid in swimmingslithering o Ostrichs and kiwis w reduced wings I cannot fly o Cavedwelling fish w eye sockets I eyeless and blind o Humans w reduced coccyx tail bone I does not aid in balancing o Humans w goosebumps I does not provide warmth Current Examples of Change Through Time I Bacteria evolved to resist antibiotics I Insects evolved to resist pesticides I Weeds evolved to resist herbicides I Timing of bird migrationemergence of insectsblooming of flowering plants evolved in response to climate change Evidence of Descent from a Common Ancestor o Are species related to one another Similar Species Are Found in the Same Geographic Area I Galapagos finches and mockingbirds very similar according to Darwin I Descent w modification supported with DNA evidence I Phylogenetic tree branching diagram describing the ancestor descendant relationship among species taxa Similar Species Share Homologies I quotThe study of ikeness I Example human hair and dog fur are homologous I Genetic homology o occurs in DNA nucleotides o example eyesless gene in fruit flies and Aniridia gene in humans produce 90 homologous amino acid sequences Developmental homology o occurs in embryos o example chick human and cat embryos have tails and gill pouches early in development but become vestigial I Structural homology o similar to morphology o example turtles humans horses birds bats and seals have homologous limb structure Evoution s quotInternal Consistency The Importance of Independent Data Sets o Internal consistency support from multiple independent sources 42 Evolution by natural selection Chapter 253 The Process of Evolution How does Natural Selection Work Darwin39s Inspiration 0 Pigeon breeding crossbreeding of desired traits artificial selection 0 quotAn Essay on the Principles of Population by Thomas Robert Malthus concluded that more individuals are born than can survive so they compete for foodsheltersurvival Darwin39s Four Postulates 0 Four postulates o Individuals in a population vary in traits they possess o Trait differences are heritable o More offspring produced than can survive those that survive produce more offspring o Parents of offspring have certain advantageous traits 0 Outcome of natural selection a change in allele frequency in a population over time 0 Definition Heritable variation leads to differential reproductive success The Biological Definitions of Fitness Adaptation and Selection 0 Biological fitness ability of the individual to produce surviving fertile offspring relative to others in the population measure of quantity 0 Biological adaptation heritable trait that increases fitness of an individual in a particular environment relative to individuals lacking the trait 0 Opposite of adaptation neutral trait eg hair color Chapter 254 Evolution in Action Recent Research on Natural Selection Case Study 1 How did Mycobacterium tuberculosis become resistant to antibiotics 0 TB infects the lungs and causes fever coughing sweats weight loss death 0 Advances in nutrition and antibiotics decreased importance of TB 0 In 1993 WHO declared TB as a global health emergency drug resistant A Patient History o Admitted with active TB infection o Given antibiotics for six weeks followed by twiceweekly doses of rifampin for 33 additional weeks o Ten months of therapy culture showed no TB o Two months later patient readmitted w active TB resistance to antibiotics including rifampin death due to respiratory failure ten days later 0 Examination of M tuberculosis DNA showed a print mutation in a gene called rpoB A Mutation in a Bacterial Gene Confers Resistance 0 rpoB codes for a component of RNA polymerase which transcribes DNA to mRNA o Cytosine changed to thymine amino acid serine changed to leucine o Change of protein shape antibiotic can39t bind o Few bacteria w mutation rifampin kills normal bacteria mutated bacteria reproduce new population resist to drug Testing Darwin39s Postulates o Was the trait heritable o rpoB is passed onto offspring o phenotype due to genotype o Was there variation in reproductive success o small number of bacteria survived first round of antibiotics o Did selection occur o in presence of antibiotics mutated bacteria selected o Natural selection acts on individuals but populations evolve Case Study 2 Why Are Beak Size Beak Shape and Body Size Changing in Galapagos Finches 0 Peter and Rosemary Grant study finches on Daphne Major in the Galapagos Selection during Drought Conditions 1977 drought 84 finches disappeared Natural experiment compare treatment groups by unplanned change in environment o Survivors tended to have deep beaks Continued Changes in Environment Continued Selection Continued Evolution o 1983 heavy rain sma beaked finches reproduced rapidly Why Genes Are Under Selection o Polygenic difficult to identify o Clifford Tabin s lab studies beak development by looking at variation in cell expression of cellcell signals important to development of chicken beaks o In situ hybridization showed where cellcell signal gene called Bmp4 is expressed o Strong correlation between amount of Bmp4 expressed and the widthdepth of adult beak o Suggests that alleles for molecule called calmodulin involved in calcium signaling affects beak length 43 Mendel Monohybrid and dihybrid crosses Chapter 141 Mende s Experimental System o Heredity transmission of traits from parents to offspring o Trait characteristic of an individual eg height membrane protein What Questions Was Mendel Trying to Answer I What are the basic patterns in the transmission of traits from parents to offspring I Two hypotheses I Blending inheritance traits observed in motherfather blend I Inheritance of acquired characters traits present in parents are modified through use and passed on to offspring The Garden Pea Served as the First Model Organism in Genetics I Inexpensive easy to group short generation time produce large of seeds I Model organism a species used for research because it is practical results can apply to other organisms I Each plant had different recognizable traits and mating could be controlled How Did Mendel Control Matings I Selffertilization a fower s pollen falls on the female organ of the same flower I Cross fertiization transfer of pollen from one plant to another What Traits Did Mendel Study I Seven traits 0 Seed color 0 Seed shape 0 Pod shape 0 Pod color 0 Flower color 0 Flower and pod position 0 Stem length I Phenotype observable trait I Pure line individuals that produce offspring identical to themselves when they are selfpollinated or cross w another pure line I Hybrids offspring from mating between truebreeding parents that differ in one or more traits Vocabulary for Mendelian Genetics 0 Gene a hereditary factor that influences a particular trait 0 Allele a particular form of a gene o the two alleles in a diploid may be the same or different 0 Genotype a listing of the alleles in an individual o in diploids the genotype lists two alleles of each gene o in haploids the genotype lists one allele of each gene 0 Phenotype an individual s observable traits can be observed at levels from molecule to the whole organism influenced not dictated by the genotype 0 Homozygous having two of the same alleles 0 Heterozygous having two different alleles 0 Dominant alleles an allele that produces its heterozygous and homozygous form dominance does not imply high frequency or high fitness 0 Recessive allele an allele that produces its phenotype only in homozygous form phenotype quotrecedes or disappears in heterozygous individuals 0 Reciprocal cross a cross in which the phenotypes of the male and female are reversed compared with a prior cross o If reciprocal crosses give identical results the sex of the parent does not influence transmission of the trait 0 Testcross a cross between a homozygous recessive individual and an individual with the dominant phenotype but an unknown genotype o Usually used to determine whether a parent with a dominant phenotype is homoheterozygous 0 X Linked referring to a gene located on the X chromosome 0 X Linked genes and traits show different patterns of inheritance in malesfemales 0 Y inked referring to a gene located on the Y chromosome o In humans Y inked genes determine mae specific development 0 Autosomal referring to a gene located on any nonsex chromosome an autosome or a trait determined by an autosomal gene o Mendel studied only autosomal genes and traits Chapter 142 Mende s Experiments with a Single Trait 0 Parental generation adults used in an initial experiment cross 0 F1 generation progeny first filial The Monohybrid Cross P gaiI11et e 5 rnu rid pare nt Fll Flt F39 1311quot39E lE5 r RT Rf 39lIl39lil39I39lfquotIlEI39E39d FITEFE t r Hr Rn o Results contrast bending inheritance hypothesis Dominant and Recessive Traits o Monohybrid cross mating between parents w two different genetic determinant for the same trait o Wrinkled shape is recessive relative to round seed o Round seed is dominant relative to wrinkle seed o Individuals w the dominant phenotype do not necessarily have higher fitness than individuals w the recessive phenotype 0 Dominant and recessive identify only which phenotype is observed in individuals carrying two different genetic determinants for a given trait A Reciprocal Cross o Mendel wanted to test whether gender influenced inheritance of seed shape o Same outcome as before Do Mende s Results Hold for Other Traits o Followup experiments showed 3 to 1 ratio in F2 generation in other traits Particulate Inheritance Particulate inheritance hereditary determinants maintain their integrity from generation to generation they act as discrete entities or particles The Principle of Segregation o The two members of each gene pair must segregate into different gamete cells during the formation of eggs and sperm resulting in one allele of each gene within each gamete Predicting Offspring Genotypes and Phenotypes with a Punnett Square o Gamete genotype of one parent on horizontal row and other parent on vertical


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