File:Maylandia lombardoi.jpg Obrázek1 Alfred_Russel_Wallace_-_Project_Gutenberg_eText_14558 File:Charles Darwin.jpg File:Darwin's finches.jpeg File:Life cycle of a sexually reproducing organism.svg File:Biston.betularia.7200.jpg File:Biston.betularia.f.carbonaria.7209.jpg File:Heliconius mimicry.png untitled Evolution by natural selection: Oválný popisek: All organisms produce more offspring than can survive and reproduce. All organisms produce more offspring than can survive and reproduce. Oválný popisek: Individuals (genotypes) differ in heritable traits related to survival and reproduction. Individuals (genotypes) differ in heritable traits related to survival and reproduction. Oválný popisek: The genotypes differ in their contribution to the next generation, ie. the most fit genotypes contribute more than the less fit ones. The genotypes differ in their contribution to the next generation, ie. the most fit genotypes contribute more than the less fit ones. Rock pocket mouse (Chaetodipus intermedius): Sonoran and Chihuahuan Des. dd DD, Dd 60-98% survival relative to dark individuals http://www.evolution-textbook.org/content/free/figures/17_EVOW_Art/02_EVOW_CH17.jpg Selection on the RNA level: invariant position intron Tetrahymena: Ca+ instead of Mg+ (normal state) increase in activity after 12 generations frequency of 9 variants mutant position REPRODUCTIVE FITNESS, w = average per capita lifetime contribution of individuals of a given genotype to the population after one or more generation absolute number of the offspring = absolute fitness discrete generations, stable population ® fitness » 1 in asexual organisms, » 2 in sexual organisms; even with a slight deviation the population goes either to extinction or to overpopulation continuous time scale ® growth rate » 0 in evolution relationships between genotypes in a population more important ® relative fitness discrete time ® = ratio of absolute fitness; continuous time ® = difference between growth rates usually relative fitness of the most fit genotype = 1 alternatively we may relate to the mean population fitness http://static.ddmcdn.com/gif/mice-stem-cells-101209-675634-.jpg Total number of offspring Quality of the weaned offspring Components of fitness: Maternal behaviour Milk production Viability Reproductive success Litter size Litter frequency Number of litters Resistance to pathogens Escape from predators Frequency of ovulations Survival of embryos Size of mammary glands zygotic selection: gametic selection: viability reproductive success fertility/fecundity gamete viability fertilisation success segregation distortion http://www.thefutureofhealthnow.com/wp-content/uploads/2013/07/IVF.jpg http://www.zoo.ox.ac.uk/egi/wp-content/uploads/2013/07/Raggiana-Bird-of-Paradise-copy.png popg.jpg http://www.basinandrangewatch.org/images/Pisgah-lavahabitat.jpg Change of allele frequencies and selection coefficient, s http://modeling-natural-selection.wikispaces.com/file/view/rock_pocket_mouse_tan.jpg/281549398/rock _pocket_mouse_tan.jpg Fitness in the pocket mouse: AA 1 Aa 1 aa 1 ‒ s mean s(aa) » 0,20 w = 0,60‒0,98 Þ s = 0,02‒0,40 Increase of beneficial dominant allele A: When s = 0,20 and initial frequency A = 0,01 the freq. increases to 0,95 in ca. 120 generations negatively proportional to the mean fitness of the population Þ with increasing frequency of the beneficial allele the evolution is slowing down; if q or p = 0 Dp = 0 biggest change when p=q=0,5 frequency of A Select1 Increase of a advantageous dominant allele A: the higher s (ie. stronger selection), the more rapid change Selekce_1.tif p0 = 0,005 Selection and dominance frequency of a recessive allele increases very slowly, then very rapidly frequency of a dominant allele increases very rapidly, then very slowly the most rapid fixation with codominance p0 = 0,05 Effect of the initial allele frequency: > STUDY OF NATURAL SELECTION: 1. Correlation of allele frequencies across populations ADH AdhF in D. melanogaster 2. Deviations from expected genotype frequencies (HW) [USEMAP] 3. Temporal changes of a trait: industrial melanism in the peppered moth (Biston betularia) in Britain „typica“ „carbonaria“ Biston 4. Experimental evidence: H.B.D. Kettlewell Birmingham (znečištěná oblast) Světlá forma (typica) Tmavá forma (carbonaria) Počet zpětně odchycených: pozorovaný 18 140 očekávaný 36 122 Relativní míra přežívání 0,5 1,15 Relativní fitness 0,5/1,15 = 0,43 1,15/1,15 = 1 Deanend Wood (neznečištěná oblast) Světlá forma (typica) Tmavá forma (carbonaria) Počet zpětně odchycených: pozorovaný 67 32 očekávaný 53 46 Relativní míra přežívání 1,26 0,69 Relativní fitness 1,26/1,26 = 1 0,69/1,26 = 0,55 http://shawmst.org/biology/files/2010/07/Evolution28.png polluted area non-polluted area light dark relative fitness Problems: 3 alleles, not 1, affect the colouration increase of melanism also in species not endangered by predation by insectivorous birds (pigeons, cats, some beetles) in some areas correlation between melanism and pollution weak errors in the experiment: during the day, peppered moths stay on horizontal branches, not on trunks (different lichen species); in butterflies and birds different perception of UV under laboratory conditions the typica viability by 30% lower than that of carbonaria better absorption of solar radiation in melanic forms? (eg. two-spot ladybird) industrial melanism of B. betularia in Britain 5. Resistance DDT eg.: DDT resistance in mosquitos (Aedes, Anopheles): Warfarin Warfarin = blood anticoagulant, inhibiting the enzyme responsible for the recovery of vitamin K (coagulation cofactor) dramatic increase of the resistance allele R after Warfarin application relative to the resistance R allele dominant but relative to the increased demand of vitamin K recessive eg.: Warfarin resistance in rats: Relationship between phenotype and fitness: basic selection regimes Select5 directional these phenotypes are disadvantageous original mean consistent change of environment shift of the mean variance unchanged Select5 stabilizing stable environment mean unchanged lower variance highest fitness in individuals with intermediate (mean) phenotypes Relationship between phenotype and fitness: basic selection regimes directional consistent change of environment shift of the mean variance unchanged Select5 disruptive heterogenous environment intermediate phenotypes disadvantageous higher variance stabilizing stable environment mean unchanged lower variance Relationship between phenotype and fitness: basic selection regimes directional consistent change of environment shift of the mean variance unchanged Birth stabilizing selection – birth weight in humans mortality (logarithmic scale) Mut_sel.jpg Equilibrium between selection and mutation recurrent emergence of a deleterious mutation ´ elimination by selection equilibrium s q μ = dominance: s q μ = recessivity: Muller-Haldane principle: Regardless of dominance/recessivity of a deleterious mutation, its impact on decreasing fitness is independent of the level of its harmfulness. weaker selection Þ higher frequency complete recessivity (h = 0) Þ higher frequency 1. m>s Þ allele fixation 2. m waa Over.jpg Selection maintains balanced polymorphism frequency of the more common allele decreases frequency of the rarer allele increases balanced polymorphism wAA < wAa > waa Eg.: sickle cell anemia and malaria http://mathildasanthropologyblog.files.wordpress.com/2008/04/bantu-1.gif http://www.south-africa-tours-and-travel.com/images/zulus-ploughing-their-land-bantu.jpg ~ 2000 years ago expansion of Bantu peoples burning off savannas and forests, increase of population density ® suitable environment for Anopheles mosquitos (A. gambiae), the host of Plasmodium falciparum Þ malaria http://ucce.ucdavis.edu/files/repository/calag/img6102p58b.jpg sickle cell anemia malaria sickle cell anemia: S allele: substitution of 1 AA at 6th position in 6th codon of the b-Hb gene: http://faculty.southwest.tn.edu/rburkett/gb%20-%20F50.jpg Sickle cell anemia and malaria: Figure A shows normal red blood cells flowing freely in a blood vessel. The inset image shows a cross-section of a normal red blood cell with normal hemoglobin. Figure B shows abnormal, sickled red blood cells clumping and blocking blood flow in a blood vessel. (Other cells also may play a role in this clumping process.) The inset image shows a cross-section of a sickle cell with abnormal hemoglobin. at low O2 concentrations ® production of elongated crystals Þ anemia AS – only transmission of anemia, SS – strong anemia http://wiki.ggc.edu/images/9/94/2HBSborder.gif http://evolution.berkeley.edu/evolibrary/images/evo/hemoglobin.gif Relative fitness of genotypes related to sickle cell anemia: File:Plasmodium falciparum 01.png sickle-cell red blood cell invaded by Plasmodium is rapidly breaking Þ the parasite cannot reproduce and multiply Þ resistance ® heterozygote advantage File:Sicklecells.jpg Phenotypes related to the S allele: 1. Electrophoretic mobility both alleles are codominant + AA AS SS start 2. Sickling sickling in SS and AS individuals Þ with respect to deformation S dominant http://medicalassessment.net/images/sickle-cell-anemia.jpeg AA AS SS normal erythrocyte sickled erythrocyte sickled erythrocyte 3. Anemia in SS individuals longer chains Þ stronger deformation of red blood cells Þ more fatal impacts on the organism: erythrocyte rupture (anemia), clogging of capillaries etc. clinical syndromes only in SS Þ S allele recessive AA AS SS healthy individual healthy individual anemic individual Phenotypes related to the S allele: 4. Resistance to malaria with respect to resistance the S allele dominant AA AS SS absence of resistance resistance resistance Phenotypes related to the S allele: AA AS SS viable individual lethality 5. Phenotype of health (viability) nonmalarial environment: S recessive malarial environment: SS – strong anemia; AA – malaria; AS – no anemia, weak malaria Þ S is overdominant viable individual AA AS SS malaria lethality weak malaria without anemia Phenotypes related to the S allele: Emergence of C allele in the AS polymorphism region: possible genotypes: wAC = 0,89; wSC = 0,70 wAS = 1,00 Þ selection acts against beneficial allele! Although C higly beneficial, selection will decrease its frequency until it is completely removed!! http://upload.wikimedia.org/wikipedia/commons/2/26/Red_Blood_Cell_abnormalities.png Resistance against malaria can be mediated through other mechanisms: hemoglobin E (JV Asie) a- a b-thalassemia G6PD*) deficiency Pk**) deficiency etc. etc. *) glucose-6-phosphate dehydrogenase **) pyruvate kinase However, selection in favour of heterozygotes is not widespread in nature Alternative equilibrium: selection against heterozygotes (underdominance) heterozygote fitness is lower than w of homozygotes wAA > wAa < waa Under.jpg above the critical level ® fixation Selection results in fixation of one of the alleles (and extinction of the other) below the critical level ® extinction non-stable equilibrium wAA > wAa < waa 2. Selection in heterogeneous environment environmental variation: spatial temporal coarse-grained: single environment throughout lifetime fine-grained: environmental heterogeneity throughout lifetime selection: soft hard Hardsoft selection hard Silene vulgaris ssp. humilis Minuartia verna Coarse-grained environment and soft selection will maintain polymophism in the population with higher probability than fine-grained environment and hard selection. soft selekce hard Hardsoft 3. Antagonistic selection different sexes different ontogenetic stages gametic ´ zygotic phase Freq_dep_new.jpg with increasing frequency, fitness of A allele decreases 4. Frequency-dependent selection I. Negative Obrázek1 Eg.: Batesian mimicry [in this case it is rather density-dependent selection] Soubor:Red milk snake.JPG File:Batesplate ArM.jpg Soubor:Micrurus tener.jpg Periss3 Periss1 Eg.: cichlid Perissodus microlepis (Tanganyika) frequency  II.jpg „right-mouthed“ „left-mouthed“  Freq_dep_new.jpg with increasing frequency, fitness of A allele increases 4. Frequency-dependent selection II. Positive http://graphics8.nytimes.com/images/2013/03/12/science/12CREA/12CREA-superJumbo.jpg Müllerian mimicry: Heliconius melpomene H. erato Amereega hahneli (poisonous) Lithodytes lineatus (harmless; Batesian mimicry) R. variabilis (poisonous) R. ventrimaculata (poisonous) Ranitomeya imitator (d,f; poisonous) Heliconius erato H. melpomene Balancing selection at the molecular level: untitled adh comparison of observed and expected polymorphism in the ADH gene MHC genes chimpanzee alleles (C) more similar to human alleles (H) than other C alleles