Evolution Evolution Chapters 22-25 Changes in populations, species, or groups of species. Variances of the frequency of heritable traits that appear from one generation to the next. 2 Areas of Evolutionary Study Agree or Disagree Microevolution Details of how populations of organisms change. Generation to Generation New species origninate Macroevolution Patters of change in groups of related species. Broad period of geologic time Patterns determine phylogeny. The evolutionary relationships among species and groups of species For each of the following statements decide if you agree that this is how evolution occurs or disagree. After you have agreed or disagreed choose 2 agree statements and site examples and 2 disagree statements and site examples. Lamarck Use and Disuse 3 ideas for evolution: Use and Disuse Inheritance of acquired characteristics Natural Transformation of species How body parts of organisms can develop with increased usage, while unused parts weaken. 1
Inheritance of Acquired Characteristics Described how body features acquired during the lifetime of an organism could be passed on to offspring. Natural Transformation of Species Organisms produced offspring with changes, transforming each subsequent generation into a slightly different form toward some ultimate higher order of complexity. Species did not become extinct nor did they split and change into two or more species. More organisms are born than needed to maintain the population overproduction competition variation adaptation Organisms compete for limited natural resources such as food, water, shelter and space. competition variation adaptation Organisms within a population vary. Variation is heritable. Any inherited trait that increases the chances of survival. Fitness is determined by the environment. variation adaptation adaptation 2
Individuals with favorable variations (adaptations) are more likely to survive and pass on these traits to their offspring Survival of the Fittest Favorable variations (adaptations) gradually accumulate and unfavorable variations disappear over many generations Eventually this leads to a new species Evolution and Speciation 4 Different types of Selection Stabilizing Selection Disruptive Selection Directional Selection Sexual Selection Artificial Selection Sources of Variation Mutations Mutations Sexual Reproduction Diploidy Outbreeding Balanced Polymorphism Raw material for new variation. Invents new genes that were never in the gene pool before. 3
Sexual Reproduction Diploidy Creates individuals with new allele frequencies. Genetic Recombination- 3 events Crossing Over Independent Assortment of Homologues Random Joining of Gametes The presence of 2 copies of each chromosome in a cell. Recessive alleles are hidden in the gene pool. Outbreeding Mating of unrelated partners. Increases the possibility of mixing different alleles and creating new combinations. Balanced Polymorphism Maintenance of different phenotypes in a population. Heterozygote Advantage The heterozygote condition bears a greater selective advantage. (Sickle Cell in Africa) Hybrid Vigor/ heterosis Superior quality of offspring resulting from crosses between 2 different inbred strains of plants. Frequency-dependent selection Least common phenotypes have a selective advantage. Predator mimicking prey. Causes of Changes in Allele Frequencies Mutations Gene Flow Genetic Drift Nonrandom Mating Gene Flow The introduction or removal of alleles from the population Immigration Emigration 4
Genetic Drift Nonrandom Mating A random increase or decrease of alleles. 2 Types Founder Effect Alleles in a group of migrating individuals are not the same as that of the origin population. Bottleneck Population undergoes a dramatic decrease in size due to a natural catastrophe. Individuals choose mates based upon their particular traits. Inbreeding Sexual Selection How do we know evolution is occuring? Hardy-Weinberg 5 Conditions for Hardy-Weinberg Equilibrium (evolution is not happening) All traits are selectively neutral Mutations do no occur No gene flow No genetic drift Random mating Genetic Equilibrium Determination Allele frequencies for each allele p is for the dominant allele q is for the recessive allele Frequency of homozygotes p 2 is for the homozygous dominant q 2 is for the homozygous recessive Frequency of heterozygotes pq + qp = 2pq Equations Example Problem p + q= 1 p 2 + 2pq + q 2 = 1 Suppose a plant population consists of 84% plants with red flowers and 16% with white flowers. Assume the red allele (R) is dominant to the white allele (r). 5
Do Hardy-Weinberg conditions meet any population? NO! Why bother learning it? Starting point Further investigation as to which condition is being violated Mechanisms of evolution Evidence for Evolution Paleontology Biogeography Embryology Comparative Anatomy Molecular Biology Speciation Allopatric Speciation Species Speciation The formation of a new species by one of 4 processes Allopatric Sympatric Sympatric by Polyploidy Adaptive Ratiation Population is divided by a geographic barrier. Barrier creates isolation of breeding. Species continue to evolve by natural selection (if environments are different), mutation, genetic drift. Sympatric Speciation Sympatric Speciation by Polyploidy The formation of a species without the presence of a geographic barrier. Balanced Polymorphism Camouflage and Mimicry Hybridization The posession of more than the normal two sets of chromosomes (2n). Polyploidy occurs as a result of nondisjunction of all chromosomes during meiosis. A tetraploid can occur when two diploid gametes come together. Reproductive Isolation thus 6
Adaptive Radiation Maintaining Reproductive Isolation Rapid evolution from a single species Adapts to geographic or ecological conditions. Darwin s Finches Necessary for Prezygotic Isolating Mechanisms Postzygotic Isolating Mechanisms Prezygotic Isolating Mechanisms Postzygotic Isolating Mechanisms Habitat Isolation Temporal Isolation Behavioral Isolation Mechanical Isolation Gametic Isolation Hybrid Inviability Hybrid Sterility Hybrid Breakdown Patterns of Macroevolution Phyletic Gradualism Phyletic Gradualism Punctuated Equilibrium Gradual Accumulation of small changes. Fossil evidence provides snapshots of the evolutionary process. 7
Punctuated Equilibrium The Earth and its atmosphere formed. Long periods of no evolution stasis followed by quick bursts of evolution. Consisted of CO, Carbon dioxide, hydrogen gas, nitrogen gas, water, sulfur, and hydrochloric acid. Little or no oxygen gas. The primordial seas formed The earth cooled, gases condensed to produce seas consisting of water and minerals. Complex molecules were synthesized. Miller-Urey Experiment Oranic molecules were formed from inorganic molecules with help from energy. Polymers and self-replicating molecules were synthesized. Monomers combined to form polymers. Proteinoids Abiotically produced polypeptides Organic molecules were concentrated and isolated into protobionts. Protobionts Cell precursors. Able to carry out chemical processes Not able to reproduce. Microspheres and coacervates 8
Primitive heterotrophic prokaryotes formed. Heterotrophs formed to take in materials. Natural selection Primitive autotrophic prokaryotes were formed. Mutation for an autotroph to be formed. Produces oxygen as a product of chemical processes. Oxygen and the ozone layer formed and abiotic chemical evolution ended. Oxygen released in the atmosphere. Ozone layer made. UV light was filtered. Major source of energy was eliminated. Eukaryotes formed Endosymbiotic Theory 9