bio 112 final unit 1

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Terms in this set (91)
Internal ConsistencyObservation that data from independent sources agree in supporting predictions made by a theoryDarwin's Postulates1. Varying traits in individuals of a population 2. Some differences are heritable and are passed on to offspring 3. More offspring are produced than can survive 4. Individuals with certain heritable traits are more likely to survive and reproduceBiological FitnessThe ability of an individual to produce offspring, relative to that ability in other individuals in the populationAcclimationOccurs when an individuals phenotype changes in response to changes in the environment, but an individual's genotype remains fixed; the changes are not passed down to offspringAdaptationOccurs when the allele frequencies in a population change in response to natural selectionMisconceptions of Evolution1. Not goal-directed 2. Not progressive 3. No "higher" or "lower" organismsNonadaptive TraitsTraits that are not adaptiveGenetic CorrelationOccurs when selection favoring alleles for one trait causes a correlated but suboptimal change in an allele for another trait; occurs because of pleiotropyPleiotropyWhen a single allele affects multiple traitsFitness Trade offsCompromise between traits, in terms of how those traits are adapted for the environment. Ex. size of eggs that an individual makes and the number of offspring it can produceHistorical ConstraintsAdaptations that are constrained by history because all traits evolve from previously existing traitsDirectional SelectionPattern of natural selection that increases the frequency of one allele; reduces a population's genetic diversity over timePurifying SelectionWhen disadvantageous alleles decline in frequency;happens with continuous directional selection over timeStabilizing SelectionPattern of natural selection that occurs when individuals with intermediate traits reproduce more than others, thereby maintaining intermediate phenotypes in a population; no change in average value of a trait over time and genetic variation is reducedDisruptive SelectionPattern of natural selection that occurs when intermediate phenotypes are selected against and extreme phenotypes are favored; maintains genetic variation by does not change the mean value of a trait; can cause speciationSpeciationFormation of new species, if individuals with one extreme of a trait start mating preferentially with individuals that have the same traitBalancing SelectionNo single allele has a distinct advantage; variation of enviroment over time, heterozygote advantage and frequency- dependent selection contribute to thisHeterozygote AdvantageHeterozygous individuals have higher fitness than homozygous individuals do; maintains genetic variation in the populationFrequency Dependent SelectionPattern where certain alleles are favored when they are rare, but not when they are common; genetic variation is maintained or increasedSexual SelectionSpecial form of natural selection that occurs when individuals in a population differ in their ability to attract mates; it favors individuals with heritable traits that enchance their ability to obtain matesFundamental Asymmetry of SexResults from the fact that in, most species, females usually invest more in their offspring than males doFemale ChoiceType of sexual selection that allows females to be choosy about their mates. Most females choose mates based on physical characteristics and prefer males that care for young/provide the resources required to produce eggsMale-Male CompetitionMales compete intensely for the opportunity to mate with femalesSexual DimorphismRefers to any trait that differs between males and females of the same species; consequence of sexual selection. Ex. manes on male lionsBiological Species ConceptConsiders populations to be evolutionarily independent if they are reproductively isolated from each otherPrezygotic IsolationOccurs when individuals of different species are prevented from matingPostzygotic IsolationOccurs when individuals from different populations do mate, but the hybrid offspring produced have low fitness and do not survive or produce offspringHabitat IsolationPrezygotic barrier in which 2 species encounter eachother rarely or not at all because they occupy different habitats, even though not isolated by physical barriersTemporal IsolationSpecies that breed at different times of the day, different seasons, or different years cannot mix their gametes; prezygotic barrierBehavioral IsolationCourtship rituals and other behaviors unique to a species are effective barriers; prezygotic barrierMechanical IsolationMorphological differences can prevent successful mating; prezygotic barrierGametic IsolationPrezygotic barrier that involves sperm of one species not being able to fertilize eggs of another speciesReduced Hybrid ViabilityGenes of the different parent species may interact and impair the hybrid's development; postzygotic barrierReduced Hybrid FertilityEven if hybrids are vigorous, they may be sterile; postzygotic barrierHybrid BreakdownSome first-generation hybrids are fertile, but when they mate with another species or with either parent species, offspring of the next generation are feeble or sterileDisadvantages of Biological Species Concept1. Can not use with fossils 2. Can not use with asexual organisms 3. Can only be applied to populations that overlap geographicallyMorphospecies ConceptIdentify evolutionarily independent lineages by differencs in morphological featuresDisadvantages of Morphospecies Concept1. Subjective 2. Can not identify species that differ in non-morphological traitsPhylogenetic Species ConceptBased on reconstructing the evolutionary history of populations; a species is defined as the smallest monophyletic group on the tree of lifeCladeAn ancestral population plus all of its descendantsSynapomorphiesHomologous traits inherited from a common ancestor that are unique to certain populations or lineagesDisadvantages of Phylogenetic Species Concept1. Phylogenies are only avaliable for a tiny subset of populations 2. It will probably lead to the recognition of many more species than either of the other species conceptsSubspeciesPopulations that live in discrete geographic areas and have their own identifying traits but are not distinct enough to be considered a separate speciesAllopatric SpeciationSpeciation that begins with physical isolation via either dispersal or vicarianceDispersalOccurs when a population moves to a new habitat, colonizes it, and forms a new populationVicarianceOccurs when a physical barrier splits a widespread population into subgroups that are physically isolated from each otherSympatric SpeciationPopulations or species that live (close enough to mate) in the same geographic area; natural selection overcoming gene flowPolyploidyThe condition of having more than two sets of chromosomes, usually in plants; can cause speciationAutopolyploidyMutations that result in doubling of chromosome number, with the chromosomes all coming from the same speciesAllopolyploidyMutations that result in doubling of chromosome number, with the parents belonging to different specieReinforcementSelection for traits that isolates populations reproductively; strong natural selection against interbreedingHybrid ZonesA geographic area where interbreeding between two populations occurs and hybrid offsping is commonGametogenesisFormation of gametes in the reproductive organs of adult organismHeadPart of the sperm that contains the nucleus and the acrosomeAcrosome EnzymesAllow sperm to penetrate the egg's barriers; located in the headNeckPart of the sperm that encloses a centriole that will fuse with the egg's centriole to form a chromosomeMidpiecePart of the sperm that is packed with mitochondria, which produce the ATP necessary for movementTailThe part of the sperm that contains the flagellum, which acts as a propellerYolkThe embryo's sole source of nutrition prior to hatching; produced only by egg laying speciesCytoplasmic DeterminantsIn the egg; controls the early events of developmentCortical GranulesIn the egg, small enzyme-filled vesicles that are activated during fertilization; In mammals they modify egg cell receptors to avoid fertilizationVitelline EnvelopeSurrounds the egg; called a zona pellucida in mammalsJelly LayerIn some species' eggs; thick gelatinous matrix around the vitelline envelope for more protectionFertilizationDevelopment phase where haploid sperm and egg fuse to form a diploid zygoteBindinProtein on the head of a sea urchin sperm that binds to the surface of sea urchin eggs; binds only to eggs of same speciesPolyspermyFertilization by more than one sperm; To avoid in Urchins: After fertilization, Ca2+ signal results in formation of fertilization envelope To avoid in Mammals: Cortical granules modify egg receptorsCleavageSet of rapid cell divisions that take place in animal zygotes immediately after fertilization; first step of embryogenesisEmbyogenesisProcess that makes a single-celled zygote into a multicellular embryoBlastomeresCells created by cleavage divisions, results in a blastulaBlastulaMass of blastomere cells formed at cleavage completetionGastrulationResults in the formation of embryonic tissue layers, formation of gut, and major body axes become visibleEctodermMost outer tissue layer; outer covering of adult body and nervous systemMesodermMiddle tissue layer; muscle, internal organs, and connective tissuesEndodermMost inner tissue layer; lining of digestive tract or gut and some associated organsBlastocoelFluid-filled space/cavity in the frog embryoBlastoporeSmall opening in frog embryo through which cells move during gastrulationOrganogenesisPhase where cells proliferate and become differentiated; tissue and organ formationNotochordRod-like structure that appears in the dorsal membrane which is unique to chordates (humans); key organizing event in organogenesisNeural TubeFormed in dorsal ectoderm by trigger signals from the notochord; precursor to brain and spinal cordSomitesBlocks of tissues that form on both sides of the neural tube down the length of the bodyDeterminationSomite cells differentiate in response to signals from nearby tissues