Understanding Pleiotropy, Genetic Drift, and Sexual Selection in Evolution, Exams of Biology

Download Understanding Pleiotropy, Genetic Drift, and Sexual Selection in Evolution and more Exams Biology in PDF only on Docsity! Bio 152- Evolution Exam with correct answers Natural Selection is: - ANSWERS: a process leading to differential reproductive successes among members of a population Cactus-like plants adapted for desert or dry environments are succulent (have fleshy, juicy stems) and have spines (modified leaves). Succulents can be found to occur around the world, but are classified into a number of very different families of plants based on other characteristics. That so many different kinds of succulents exist is an example of: - ANSWERS: convergent evolution T/F: meiosis acting alone could change allele frequency - ANSWERS: false T/F: natural selection acting alone could change allele frequency - ANSWERS: true T/F: genetic drift acting alone could change allele frequency - ANSWERS: true What are the two major sources of genetic variation in a population? - ANSWERS: mutation and recombination T/F: evolution in a rapidly reproducing population can be faster because the mutation rates per gene locus are faster in small populations compared to large populations - ANSWERS: false T/F: evolution in a rapidly reproducing population can be faster because random events can have larger effects on allele frequencies - ANSWERS: false T/F: evolution in a rapidly reproducing population can be faster because more reproductive events per unit time translates into more possible changes per unit time - ANSWERS: true T/F: the rate at which a particular kind of mutation occurs is independent of the fitness of the resulting allele - ANSWERS: true Which condition of HW equilibrium is being violated? : In a particular region of the coast, limpets (a type of mollusc) live on near shore habitats that are uniformly made up of brown sandstone rock. The principle predators of these limpets are shorebirds. The limpets occur in two morphs, one with a light colored shell and one with a dark colored shell. The shorebirds hunt by sight and are able to see the light ones on the dark sandstone easier than the dark ones. - ANSWERS: No selection Which condition of HW equilibrium is being violated? : In Chen caerulescens (a species of goose), the white body form, the snow goose and the blue body form, the blue goose, occasionally coexist. In these areas of contact, white by white and blue by blue matings are much more common than white by blue matings. - ANSWERS: Random Mating Which condition of HW equilibrium is being violated? : Prior to the Mongolian invasions which occurred between the 6th and 16th centuries, the frequency of blood type B across Europe was close to zero. The frequency of blood type B among the Mongols was relatively high. Today, it is possible to see fairly high frequencies of blood type B in the eastern European countries and a gradual decrease in the frequency of blood type B as one moves from the eastern European countries to the western Europe - ANSWERS: No migration T/F: Populations rather than individuals undergo evolution - ANSWERS: true T/F: Natural selection acts on individuals within a population - ANSWERS: true T/F: Natural selection is the only factor that can lead to evolution - ANSWERS: false T/F: Genetic drift (changes in allele frequencies due to chance alone) should have a greater impact in small populations - ANSWERS: true Which of the following was true about Charles Darwin? A. He believed that evolution was due to the inheritance of acquired characteristics. B. He supported Lamarck's explanation of how evolution occurred. embryology - ANSWERS: compare embryos of different species and look for homologous structures vertical transfer - ANSWERS: parent to offspring horizontal transfer - ANSWERS: unrelated to unrelated Modern Synthesis - Microevolution - ANSWERS: Evolution is the change in allele frequencies in a population over generations Selective advantage - ANSWERS: one allele picked over another because environment changes Hardy-Weinberg Equilibrium - ANSWERS: Evolution does not occur in a population unless it is acted upon by process other than Mendelian segregation or recombination. Deviation from H-W means that evolution is occurring. 5 conditions for H-W - ANSWERS: 1. large population 2. no net mutation 3. no migration 4. random mating 5. no selection 4 major evolutionary mechanisms - ANSWERS: 1. natural selection 2. genetic drift 3. mutation 4. migration evolutionary mechanism(s) that is/are adaptive - ANSWERS: only natural selection acts as a homogenizing force - ANSWERS: migration migration that results in an increase in genetic variation - ANSWERS: immigration migration that results in a reduction in genetic variation - ANSWERS: emigration random genetic drift - ANSWERS: changes in allele frequencies between generations due to random chance (sampling error) consequences of genetic drift (at allelic level and genotypic) - larger effects in smaller populations - ANSWERS: allelic: random fixation of alleles - lose some others genotypic: increase in homozygosity, loss of heterozygosity genetic drift can often lead to - ANSWERS: inbreeding bottleneck effect - ANSWERS: population's size is reduced dramatically - genetic drift can act quickly and genetic variation can greatly decrease fixation - ANSWERS: allele frequency becomes 100% consequences of inbreeding - ANSWERS: expose recessive alleles - some deleterious, usually masked in populations by heterozygote state examples of imposed genetic drift and inbreeding (2 big ones) - ANSWERS: 1. royal families 2. the amish inbreeding depression - ANSWERS: reduction in survival and fitness founder effect leads to - ANSWERS: reduced genetic variation and non-random sample of genes from original population how can natural selection lead to speciation? - ANSWERS: alter average character of a population directional selection - ANSWERS: favors extreme phenotype and causes shift in that direction, acts on both discrete and continuous traits discrete traits - ANSWERS: occurs in distinct categories - either/or continuous traits - ANSWERS: distribution of phenotypes in population varies along continuum directional selection on continuous traits - ANSWERS: results in change in distributions directional selection on discrete traits - ANSWERS: acts directly on genotype - positive selection for one, negative selection on another selection for one mouse fur color over another - ANSWERS: directional selection on a continuous trait selection for AA over aa - ANSWERS: directional selection on a discrete trait stabilizing selection - ANSWERS: acts against the extremes, favors intermediate traits selection against harmful alleles - ANSWERS: stabilizing selection for number of fingers - ANSWERS: stabilizing disruptive selection - ANSWERS: selection that favors the extremes selection that can lead to formation of new species - ANSWERS: disruptive selection from niche partitioning - ANSWERS: disruptive how do evolutionary tradeoffs constrain natural selection - ANSWERS: could be counteracting forces, a favorable trait could incur costs on a different trait (fat helps you keep warm but could also lead to diabetes) how does genetic drift constrain natural selection - ANSWERS: will interfere with the action of natural selection in small populations asymmetry of sex - ANSWERS: females - expensive and limited eggs males - harder time finding mates, greater variance in male reproduction what kind of selection is sexual selection usually - ANSWERS: directional - shift towards an extreme phenotype that attracts the most mates -phenotype is skewed towards the males who have the most reproductive success sexual dimorphism - ANSWERS: distinction between sexes- males advertise, females select fisher's runaway process - ANSWERS: keep making sexier sons good genes hypothesis - ANSWERS: traits that females choose tend to be associated with better fitness intrasexual selection - ANSWERS: competition between members of the same sex for mates intersexual selection - ANSWERS: choosy females- one sex chooses a member of the opposite sex to mate with nupital gifts - ANSWERS: food gifts it is advantageous for females to be - ANSWERS: promiscuous it is advantageous for males to - ANSWERS: prevent females from re-mating mutations - ANSWERS: sources of new alleles - genetic variation sex results in - ANSWERS: novel genotypes (NOT novel alleles) genetic recombination - ANSWERS: shuffling of alleles along chromosomes (homologous) random mating - ANSWERS: shuffling of combinations of haploid chromosomes point mutation - ANSWERS: single nucleotide change gene duplication: -followed by -results in -leads to - ANSWERS: -differentiation -new genes -gene families exon shuffling - ANSWERS: different exons either within gene or between 2 non-allelic genes are mixed (end up with new proteins) ectopic recombination - ANSWERS: recombination occurring at non-homologous chromosomes transposons/jumping genes - ANSWERS: DNA sequence that can change its relative position within genome - can be "copy and paste" (retrotransposons) or "cut and paste" (DNA transposons) polyploidy - ANSWERS: presence of extra sets of chromosomes due to accidents in cell division autopolyploid - ANSWERS: multiple sets of chromosomes - derived from one species allopolyploid - ANSWERS: multiple sets of chromosomes - derived from different species autopolyploidy results from - ANSWERS: failure to reproduce chromosome number during meiosis allopolyploidy results from - ANSWERS: hybridization between 2 species - chromosome number is not reduced most mutations are - ANSWERS: neutral, do not effect fitness mutations that matter in an evolutionary sense are - ANSWERS: those that occur in the germ line- are passed down to offspring silent mutations - ANSWERS: change nucleotide but get same amino acid (codon bias) how does meiosis contribute to genotypic variation (2 ways) - ANSWERS: 1. Recombination 2. Independent Assortment Eukaryotic recombination leads to - ANSWERS: offspring with different genotypes than their parents 4 benefits of sex - ANSWERS: 1. bring together favorable alleles quicker 2. purge bad alleles faster 3. increased genetic variation 4. evolution of individuality 5 costs of sex - ANSWERS: 1. loss of fitness relative to clonal populations 2. unnecessary males are made 3. not every male mates 2 strengths of the biological species model - ANSWERS: 1. unambiguous empirical criteria 2. clearly linked to speciation 4 problems with the biological species model - ANSWERS: 1. many species are asexual - don't interbreed 2. doesn't work for extinct species 3. many highly divergent species can hybridize (plants) 4. ability to inter-mate sometimes drops off gradually (ring species) ring species - ANSWERS: connected series of neighboring populations that can interbreed, but there exists two endpoints that are two distantly related to interbreed - but potential gene flow exists between all of the populations definition of species according to the phylogenetic model - ANSWERS: smallest monophyletic group that has a shared derived character 3 strengths of the phylogenetic model - ANSWERS: 1. easy to see evolutionary relationships on large and small taxonomic scales 2. good for extinct species 3. works for any population with phylogenetic info 4 problems of the phylogenetic model - ANSWERS: 1. good phylogenies only constructed for some species 2. ignores paraphyletic groups 3. trivial trait can make a group monophyletic - doesn't necessarily mean new species 4. lots of judgement calls involved definition of species according to phenetic (morphological) model - ANSWERS: identifies using overall similarity - usually morphology 2 strengths of phenetic model - ANSWERS: 1. most intuitive 2. easiest to do 3 problems with phenetic model - ANSWERS: 1. different species can look similar due to convergent evolution 2. populations that look distinct can belong to same group 3. speciation can occur without changes in morphology/other traits (cryptic species) Lamarck's view of evolution - ANSWERS: "Ladder of Life" - very linear what do phylogenies reflect - ANSWERS: hierarchal structuring of relationships - hypothesis about relatedness on phylogenetic tree - what does a branch point represent - ANSWERS: divergence of two species on phylogenetic tree - what are sister taxa - ANSWERS: groups that share an immediate common ancestor on phylogenetic tree - what does internal branching mean - ANSWERS: indicates that evolution is occurring on phylogenetic tree - what does a node represent - ANSWERS: speciation event what is a monophyletic group/clade - ANSWERS: consists of an ancestral taxa and all its descendants what is a polyphyletic group - ANSWERS: has more than two common ancestors what is a paraphyletic group - ANSWERS: has two common ancestors the paraphyletic species model only recognizes - ANSWERS: monophyletic groups as species Molecular Clock relies on two factors: - ANSWERS: 1. intrinsic mutation rate - how sloppy is polymerase 2. generation time more mutational differences between taxa means - ANSWERS: branched from common ancestor longer ago Mutation rate is faster if: - ANSWERS: 1. polymerase is sloppier 2. generation time is shorter what mutations are best for constructing phylogenies and why - ANSWERS: neutral - selection cannot act upon them and cause unrelated taxa to appear more similar or related taxa more different Occam's Razor - ANSWERS: simplest answer is usually the best how old is Earth - ANSWERS: 4.6 billion years Oparin and Haldane proved that - ANSWERS: early earth's atmosphere was reducing environment Muller and Urey experiments showed - ANSWERS: abiotic synthesis of organic molecules in a reducing environment is possible - able to get all 20 amino acids + other important molecules protocells - ANSWERS: vesicles + RNA capable of replication what do protocells exhibit - ANSWERS: simple reproduction and metabolism, also maintain internal chemical environment the Oxygen Revolution was due to - ANSWERS: cyanobacteria The Endosymbiotic Theory - ANSWERS: certain organelles originated as free-living bacteria that were taken in as endosymbionts -mitochondria from proteobacteria eumetzoa - ANSWERS: has true tissue diploblast - ANSWERS: endoderm and ectoderm triploblast - ANSWERS: endoderm, ectoderm, and mesoderm endoderm - ANSWERS: gut, organs ectoderm - ANSWERS: skin, nervous system mesoderm - ANSWERS: gonads, heart, connective tissue, blood radial symmetry - ANSWERS: can dissect along many planes of symmetry bilateral symmetry - ANSWERS: definite head and tail regions - gives direction of locomotion coelom - ANSWERS: fluid filled body cavity lined with mesoderm 4 perks of having a coelom - ANSWERS: 1. more space for internal organs 2. allows for larger body size 3. provides hydrostatic skeleton 4. improvements in swimming and crawling protostome - ANSWERS: spiral and determinate cleavage, mouth forms first from blastopore deuterostome - ANSWERS: radial and indeterminate cleavage, anus forms first from blastopore coevolution - ANSWERS: 2 organisms are ecologically intimate and influence each other's evolution 4 examples of coevolution - ANSWERS: 1. predator-prey 2. host - parasite/pathogen 3. plant - pollinator 4. model - mimic predator prey relationship - ANSWERS: evolutionary arms race - no one really gets ahead, example of red queen parasite tradeoff - ANSWERS: virulence vs. transmissibility plant- pollinator relationships result in 2 things: - ANSWERS: 1. directional selection 2. mutualism Batesian mimicry - ANSWERS: harmless species (mimic) will evolve appearance of toxic species (model) chordates consist of: - ANSWERS: all vertebrates plus two groups of invertebrates: urochordates and cephalochordates 4 Key Characteristics of chordates: - ANSWERS: 1. notochord 2. dorsal, hollow nerve cord 3. post-anal tail 4. pharyngeal slits/ clefts notochord - ANSWERS: provides skeletal support dorsal, hollow nerve cord - ANSWERS: made from ectoderm - becomes central nervous system post-anal tail - ANSWERS: reduces in many chordates, propelling force for aquatic chordates pharyngeal slits - ANSWERS: gils in aquatic, suspension-feeding structures in many invertebrates, important for gas exchange in non-tetrapod vertebrates, develops into parts of ears, head, and neck in tetrapods craniates - ANSWERS: chordates with heads neural crest - ANSWERS: unique to craniates - develops into some bones and cartilage of skull vertebrates - ANSWERS: craniates with a backbone 3 derived characteristics of vertebrates - ANSWERS: 1. vertebrae enclosing spinal cord 2. elaborate skull 3. fin rays - in aquatic form gnathostomes - ANSWERS: vertebrates with jaws tetrapods - ANSWERS: gnathostomes with limbs one of the most significant events in vertebrate history - ANSWERS: fins of some lobe-finned fishes evolved into feet and limbs of tetrapods 5 specific adaptations of tetrapods - ANSWERS: 1. 4 limbs plus feet with digits 2. neck - allows for separate movement of head 3. fusion of pelvic girdle to backbone 4. absence of gills (except some aquatic species) 5. ears for detecting airborne sounds tiktaalik - ANSWERS: fishapod - both fish and tetrapod characteristics