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Biology Bi111 Exam Review

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Tristan Long

Microevolution 2/8/2013 11:15:00 PM Define: Microevolution  Evolutionary change over a short period Population  All the inhabitants of a particular town, area or country Polymorphism  Existence of discrete variants of a character  Exist in two or more discrete states, and intermediate forms are often absent  Example: Snow geese have either blue or white features Gene pool  The sum of all alleles at all gene loci in all individuals Genotype frequencies  Identify the genotypes in a representative sample  The percentage of individuals possessing each genotype Phenotype frequencies  The percentage of individuals possessing each phenotype Allele frequencies  The relative abundances of the different alleles Diploid  Indivudlas genotype includes two alleles at every gene locus Haploid  Having a single set of unpaired chromosomes Null model  Mathematical model that predicts genotype frequencies: used as a null/control  Predict what they would see if a particular factor had no effect Genetic equilibrium  Point at which neither allele frequencies nor genotype frequencies change in succeeding generations Neutral mutations  Polypeptide chain, a particular amino acid can be specified by several different codons  May change an organisms phenotype without influencing its survival and reproduction (neither harmful or helpful) Gene flow  Organisms or their gametes (pollen), move from one population to another  Immigrants reproduce, may introduce novel alleles into the population they have joined Genetic drift  Occur in small populations (effects dramatically)  Occurs whenever organisms engage in sexual production, because their population sizes are not large  Leads to the loss of alleles and reduced genetic variability: population Natural selection  Beneficial, heritable traits become more common in subsequent in generations Sexual selection  Fostered the evolution of show features (brightly coloured feathers, long tails etc.) and elaborate courtship behaviour in the males of many animal species Sexual dimorphism  Differences in the size of appearance of males and females Inbreeding  Form of nonrandom mating in which individuals that are genetically related mate with each other Balanced polymorphism  When heterozygotes have higher relative fitness  When different alleles are favoured in different environments or when the rarity of a phenotype provides an advantage Frequency dependent selection  Maintained in a population simply because rare phenotypes, have higher relative fitness than more common phenotypes Neutral variation hypothesis  Some of the genetic variation at loci coding for some of the genetic variation for enzymes and other soluble proteins is selectively neutral 6.1 1. Differentiate between genetic and environmental courses of phenotypic variation  Environmental o Different phenotypes are adaptive of deleterious - result in changes in the frequency of genotypes seen in the next generation o Can influence the expression of genes, an organisms phenotype is frequently the product of an interaction between its genotype and its environment  Genetic o Organisms with different genotypes exhibit the same phenotypes: mutations o Organisms with the same genotype exhibit different phenotypes: mutations 2. Explain why genetic variation is important to Microevolutionary processes  Only genetically based variation is subject to evolutionary change 3. Describe different ways in which one could determine if variation in a trait has a genetic basis  Breeding experiments o Genetic basis of qualitative traits (flower colour in peas by crossing plants with different phenotypes) o Can change the average vault of the trait: artificial selection 4. Differentiate between quantitative variation and qualitative variation  Quantitative Variation o Traits varies continuously o Individuals differ in small, incremental ways  If you weighed everyone in your biology class, you would see that mass varies almost continuously from your lightest to your heaviest class mate  Exhibit in length of toes, the number of hairs on their hair, and their height  Qualitative Variation o Trait has distinct states o Monogenic o They exist in two or more discrete states, and intermediate forms are often absent  Snow geese either have blue or white feathers 5. Identify the sources of genetic variation in a population  Mutations o Changes in the DNA o A single mutation can have a large effect, but in many cases, evolutionary change is based on the accumulation of many mutations o Gene and chromosome mutations  Gene flow o Is any movement of genes from one population to another and is an important source of genetic variation  Sex o Can introduce new gene combinations into a population o This genetic shuffling is another important source of genetic variation  Sexual Reproduction o Recombination o Mate selection 6.2: Table 16.1 and “brown” section on pages 371-72 1. Explain why the Hardy Weinberg Principle is a “null” model  Mathematical model that predicts genotype frequencies: used as a null/control  When designing experiments, use control treatments to evaluate the effect of a particular factor  Control tells us what we would see if the experimental treatment had no effect 2. List the assumptions of the Hardy Weinberg Principle and explain how violation of these assumptions may influence genotypic and phenotype frequencies  Assumptions o Mutation is not occurring o Natural selection is not occurring o The population is infinitely large o All members of the population breed o All mating is totally random o Everyone produces the same number off offspring o There is no migration in or out of the population  Violation will cause the gene pool to change o Allele frequencies - genotype frequencies o Small population - genetic drift o Immigration/emigration -gene flow o Mutation - mutation pressure o Non random mating - Population structure 3. Explain why dominant alleles do not necessarily go to fixation (at the expense of recessive alleles)  A new recessive mutation cant be “seen” by natural selection until it reaches a high enough frequency (perhaps via the random effects of genetic drift) to start appearing in homozygotes  A new dominant mutation, is immediately visible to natural selection because it effects on fitness is seen in heterozygotes  Once an advantageous allele has reached a high frequency, deleterious alleles are necessarily rare and mostly present in heterozygotes, such that the final approach to fixation is more rapid for an advantageous recessive than for an advantageous dominant allele 4. Explain why genetic recombination does not result in changes in gene pool 5. Predict the frequencies of phenotypes and genotypes from individual crosses 6. Calculate allele frequencies based on genotypic and or phenotypic frequencies population 7. When provided with allele frequencies for an autosomal gene, predict the frequencies of phenotypes and genotypes in a random mating population 8. When provided with allele frequencies for a sex linked gene, predict the frequencies of phenotypes and genotypes in random mating population 9. Infer the dominance and chromosomal location of a gene given frequencies of phenotypes/genotypes in offspring/population 10. Hypothesize the number of alleles carried by a individual of known phenotype 6.3 1. Summarize the agents of Microevolutionary change  Mutation  Gene flow  Genetic drift  Sexual selection  Natural selection 2. Define and match the agents of Microevolutionary change and their effect on genetic variation  Mutation o A heritable change in DNA, which may be neutral, deleterious or beneficial o Over evolutionary time scales, their numbers are significant  mutations have been accumulating in biological lineages for billions of years o Deleterious mutations: alter individual‟s structure, function or behaviour in harmful ways o Lethal mutations: cause the death of organisms carrying them  Gene flow o Organisms move from one population to another o Immigrants reproduce, may introduce novel alleles into the population they have joined  Genetic drift o Chance events sometimes cause allele frequencies in a population to change unpredictably o Dramatic effects on small populations  Sexual selection o Fostered the evolution of showy structures o Intersexual selection and intrasexual selection  Natural selection o Inbreeding o Helps explain why we see different levels of genetic variation in different population  Proposes that genetic variation is directly proportional to a populations size and the length of time over which variants have accumulated 3. Differentiate between lethal, advantageous and neutral mutations  Lethal mutations o Cause the death of organisms carrying them o Allele is dominant, both homozygous and heterozygous carriers suffer o If recessive, affects only homozygous recessive individuals o Causes death before the individual reproduces  Eliminated from the population because no offspring will exist to carry the mutation onto the next generation  Advantageous mutations o Confers some benefit on an individual that carries it  Neutral mutations o Neither harmful nor helpful o Polypeptide chain: a particular amino acid can be specified by several different codons o Some different DNA changes - do not alter the amino acid sequence o May change organisms phenotype without influencing its survival and reproduction 4. Hypothesize the process by which neutral mutations arise  Changes in the polypeptide chain 5. Explain why the dominance of a lethal mutation is important to understanding an individual/population  Explain the cause of extinction 6. Explain why genetic drift and founder effects are important to conservation biologists 7. Differentiate between population bottleneck and founder effect  Population bottleneck o Disease, starvation or drought kills many individuals and eliminates some alleles from a population o Greatly reduces genetic variation even if the population numbers later rebound  Founder effect o When a few individuals colonize a distant locality and start a new population, they carry only a small sample of the parent population‟s genetic variation o Some alleles may be missing from the new population, whereas other alleles that were rare “back home” might occur at relatively high frequencies 8. Describe relative fitness in the context of natural selection and population genetics  Relative fitness o The number of surviving offspring that an individual produces compared to the number left by others in the population o Population genetics  A particular allele will increase in frequency in the next generation if individuals carrying that allele leave more offspring than individuals carrying other alleles o Natural selection  Differences in the relative success of individuals 9. Describe the effects of directional, stabilizing and disruptive selection on allele frequencies, genotype frequencies and phenotype frequencies  Directional selection o When individuals near one end of the phenotypic spectrum have the highest relative fitness o Traits mean value is higher or lower than before, depending on the direction of selection o Allele frequencies  Increases the number of one type of alleles at the sacrifice of the others, thus shifting the probability distributions in a given direction o Phenotype: favors one extreme phenotype over others o Genotype:  Stabilizing selection o When individuals expressing intermediate phenotypes have the highest relative fitness o Allele frequencies  Favors the most common allele (and traits)  Frequency of rare alleles, hence o Phenotype:  by eliminating phenotype extremes, stabilizing selection reduces genetic and phenotypic variation and increases the frequency of intermediate phenotypes o Genotype:  Disruptive selection o When extreme phenotypes have higher relative fitness than intermediate phenotypes o Alleles producing extreme phenotypes become more common, promoting polymorphism o Allele frequencies  Population is divided into subgroups that are still connected  They cans still reproduce, butt he flow of genes is reduced o Phenotype o Genotype 10. Describe how you might test for directional, stabilizing and or disruptive selection 11. Differentiate between natural and sexual selection  Natural selection o Favourable hereditary traits become more common in the next generation  Sexual selection o Has fostered the evolution of showy structures, and elaborate courtship behaviour in the males of many animal species 12. Describe the effects of sexual selection and non random on frequencies of phenotypes and genotypes  Sexual selection  Non random mating o Inbreeding generally increases the frequencies of homozygous genotypes and decrease the frequency of heterozygotes 13. Describe how you might test for adaptive variation/selection in a population  Adaptive trait o Any product of natural selection that increases the relative fitness of an organism in its environment  Testing 14. Explain the reason why inbreeding may result in lower relative fitness  Increased frequency oh homozygous resulting from inbreeding results in an increased frequency of individuals expressing a genetic disorder  If a recessive, disease causing allele is already present in the population it is more likely to end up in a zygote with another recessive allele and be expressed 16.4 1. Explain how selection against recessive allele is thwarted in diploid organism  Diploid condition reduces the effectiveness of natural selection in eliminating harmful recessive alleles form a population 2. Explain how heterozygote advantage, varying environment and frequency dependent selection can help genetic and phenotypic variation  Heterozygote Advantage o Leads to a balanced polymorphism  Two or more phenotypes are maintained in fairly stable proportions over many generations o Phenotype: o Genotype:  Frequency dependent selection o Maintained in a population because rare phenotypes have a higher relative fitness than more common phenotypes o Phenotype: o Genotype:  Phenotypic variation o Differences in appearance or function that if based on heritable information are passed from generation to generation o Phenotype: o Genotype: 16.5 1. Describe the process of adaptation and what is meant by adaptive trait  Adaptation o Accumulation of adaptive traits over time  Adaptive trait o Any product of natural selection that increases the relative fitness of an organism in its environment 2. Explain the potential constraints on adaptive evolution 3. Describe how one might test whether or not a trait is adaptive Species 2/8/2013 11:15:00 PM Define Biological species concept  Defines species in terms of population genetics and evolutionary theory in a static world: cohesiveness species Phylogenetic species concept  Species are diagnosable cluster of individuals within which there is parental pattern of ancestry and descent Ecological species concept  Species are groups of individual organisms adapted to a particular set of recourses, called a niche in the environment Morphological species concept  Organisms are classified in the same species if they appear identical by morphological (anatomical) criteria Ring species  Can exchange genetic material directly, but gene flow between distant populations occurs only through intermediary populations Clinal variation  An ecocline or cline describes an ecotone in which series of biocommunities display a continuous gradient Allopatry  Can occur when a physical barrier subdivides a large population or when a small population becomes separated from a species main geographic distribution Parapartry  Isolation may occur in a situation where a single species is distributed across a discontinuity in environmental conditions (major change in soil type) Sympatry  Reproductive isolation evolves between distinct subgroups that arise within one population  Changes in diet, behaviour, or chromosomes Species cluster  Environment experiences multiple invasions by a species (repeated many times) Hybrid zone  Some members of each population may mate with individuals from the other, producing viable, fertile offspring Autoployploidy  Having more than two sets of chromosomes all derived from the same species Alloplolyploidy  Having two or more complete sets of chromosomes derived from different species 19.1 1. Explain why it is important that we “name” species  Many similar or look alike species are tagged with the same common names which leads to miss identification  By doing this, putting an animal into a general category that does not pertain to that species particular environmental, dietary, or other aquarium care requirements 19.2 1. Explain the difference between the various “species Concepts” and the strengths and weaknesses associated with each of these concepts  Morphological Species Concept o Organisms are classified in the same species if they appear identical by morphological (anatomical) criteria o Pros  Focuses on novelties that have risen over time (diagnostic characters) o Cons  Not useful in situations where species exhibit substantial phenotypic polymorphism (belong to rings)  Not useful when there is no observable superficial phonotypical difference  Biological Species Concept o Defines species in terms of population genetics and evolutionary theory in a static world: cohesiveness species o Pros  Many „sister‟ species are hard to distinguish  Use species own perceptions to set limits  Stresses idea that species as the key unit evolutionary change, and the gene flow is the glue that holds species together  Stepping stone for studying reasons (behavioural, ecological, physiological, morphological) that underlie reproductive isolation o Cons  Can only be used in extant (not extinct) populations: no temporal dimension  Relies on reproductive isolation: not useful for species that are not sexually reproductive  Gene flow can occur even between taxa that are otherwise genetically divergent (bacterial, ring species)  Does not apply to organisms created by hybridization (a common phenomenon, especially in plants and birds)  Ecological Species Concept o Species are groups of individual organisms adapted to a particular set of resources, called a niche in the environment o Pros  Uses species own ecological usage to set limits  Differences between species in form and behaviour are often related to differences in the ecological resources that species exploits  Emphasis on selection as an important force preventing intermediate forms o Cons  Many sister species use same resources (overlapping niches)  Defining niche use can be very difficult and subjective  Many species are flexible in the niche  Can only be used in extant (not extinct) populations  Phylogenetic Species Concept o Species are diagnosable cluster of individuals within which there is parental pattern of ancestry and descent o Based on common ancestry o Pros  Considers temporal (evolutionary) nature of species  No complicated sub species designations  Not troubled by possibility that slightly different geographic forms might interbreed o Cons  Divisions based on minor differences that do not have any clear biological relevance  In uniparental species, little gene flow between lineage  If groups can still reproduce, may not remain separate species because of gene flow  Sometimes species arise from repeated events (Polyploids) are not monophyletic in origin  Practical Species Concept o Species delineations based on subjective judgment of any competent systematist o Pros  Decisions bases on careful consideration of all available information  Flexible criteria of different taxa o Cons  Not philosophically satisfying  What happens when two competent systematist disagree?  Differential Fitness Species Concept o Species are groups of individuals that are reciprocally characterized by features that would have negative effects in other groups and that cannot be regularly exchanged between groups upon contact o Pros  Allows exchange of genes  Recognizes that species specific features arise via reproductive isolation and differential selection  Reproductive isolation is not necessary (“permeable reproductive barriers”  Applicable to uniparental and biparental organisms o Cons  Can only be used easily to extant (not extinct) populations  Need to know the fitness effects of trait variation  How to deal with lineages of individuals inhabiting the same environment but carrying different selectively neutral alleles that are incompatible when combined in offspring 2. Explain why androdioeceous and gynogenetic species are not covered by the Biological Species Concept  Androdioecous Organisms o Exist as natural populations of functional males and hermaphrodites but include no true females o Lack female reproductive success  Gynogenetic Species o Have only females o Make no genetic contribution to the embryo 3. Explain why the Biological Species Concept does not apply to cases of hybridization with fertile offspring  Hybridization o The act of mixing different species or varieties of animals or plants and thus produce hybrids o Can produce fertile, partially fertile, sterile o Are not genetically distinct from other species 4. When presented with relevant biological data, determine whether or not groups can be classified as one or two “species” according to the „rules‟ of the various “Species Concepts” 19.3 1. Explain the importance of cohesiveness and distinctiveness to the various species concepts  Maintain their distinctiveness through barriers of isolation  The factors that separate populations and species are geographical, ecological, temporal, behavioural and mechanical isolation, as well as factors that inhibit the fusion of gametes or the normal development of the hybrid organism  Some isolating mechanisms (prezygotic) prevent hybrid formation; others (post zygotic) prevent hybrids from surviving and reproducing 2. Describe the possible biological processes that contribute to the cohesiveness and distinctiveness of a species  Geographic isolation o Occurs when a barrier divides a large population into two or more units (continental drift, hurricanes, mountains, glaciers)  Temporal isolation o Species living in the same habitat o Mate a different times of the day or different times of the year  Behavioural isolation o Animals rely on specific signals, to identify the species of a potential mate  Mechanical isolation (pre zygotic) o Results when differences in the structure prevent successful mating between individuals  Gamete morality (pre zygotic) o Incompatibility between the sperm of one species and the eggs of another, may prevent fertilization  Hybrid inviability (post zygotic) o Have two sets of developmental instructions, one form each parent, which may not interact properly for the successful completion of embryonic development o Hybrid die as embryos or at an early age  Hybrid sterility (post zygotic) o Some hybrids between closely related species develop into healthy adults, but don‟t produce functional gametes 19.4 1. Explain how ecology, habitat availability and behaviour can influence the distribution of individuals in the environment and the genetic patterns across a landscape  Ecology o Reduce rates of survival/ increased survival o Reduced growth/ altered development o Reduced reproductive capabilities:  Birth defects, changes in body systems (behaviour and genetic changes) o Affect the ability of a species to adapt to other environmental stresses and community interactions  Habitat availability o Not habitat available, can cause extinction o Unable to adapt to their new habitat  extinction o Survival of the fittest  Behaviour o Can affect reproductive isolation o Diet 2. Compare the amount of gene flow in species with widespread and isolated distributions, and discuss the consequences to the genetic cohesiveness and distinctiveness of the species  Widespread o Gene flow between distant populations occurs through intermediary populations o Widely distributed.. might not be able to survive certain climates  Isolated o Since requires alleles to be lost or gain, it will not occur since isolated populations have nobody coming in or out 19.5 1. Explain how genetic drift and / or selection may contribute to the patterns of genetic and morphological variation of different populations of the same species  Genetic variation o Loss of genetic variation o Only a few indivudlas contribute to the gene pool because any given allele is present in very few individuals o Leads to the loss of alleles and reduced genetic variability o Lead to a bottle neck affect  very small portion of the population is left  Must breed with each other and cause a chain of inbreeding within the species over many generations  Genetic variation decreases as similar genes are passed on to the next generation  Morphological variation
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