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  1. 1. 8/21/2013 1 JJA Obico, Instructor, Department of Biology Natural Theology Philosophy dedicated to discovering the Creator’s plan by studying nature Classify species in order to revealy p the steps of life that God had created Carolus Linnaeus - sought to discover order in the diversity of life - founder of Taxonomy Jean Baptiste Lamarck In-charge of invertebrate collection at the Natural History Museum in Paris Compared current species toCompared current species to fossil forms Use and Disuse Inheritance of Acquired Characteristics
  2. 2. 8/21/2013 2 Biological Evolution Descent with modification Charles Darwin and Alfred Wallace Descent - Transfer of genetic material to offspring overtime a. Clonal reproduction (asexual) b. Sexual reproduction Biological Evolution Modification - Change in genetic material - Mutation; genetic recombinationrecombination What evolves? Population - A group of individuals of the same species usually geographically delimited and typically have a significant amount of gene exchangeexchange Species - Consists of group generally intergrading, interbreeding populations that are reproductively isolated from other groups
  3. 3. 8/21/2013 3 Mechanisms of Evolution Genetic Drift Mutation Gene flow N d tiNon random mating Natural Selection Population Genetics (PopGen) Study of behavior of genes in the population Genetics + Evolution Mendel (1866); Darwin and WallaceMendel (1866); Darwin and Wallace (1858) Population Genetics Evolution - A change in the frequency of alleles in a population over time 1000 garden peas; 2000 alleles (TT, Tt or tt) T= 1000; t= 1000 freq of each allele= 0.5 What happens when a. T inc; t dec? b. T dec; t inc? c. Freq does not change Hardy-Weinberg Equilibrium Frequency of alleles will remain the same under the following conditions: 1. Size of population is large 2 No mutations2. No mutations 3. No migrations 4. Mating is random 5. Natural selection does not take place
  4. 4. 8/21/2013 4 Genetic Drift - Change of frequency of alleles over time due to chance a. Bottleneck effect - occurs when a catastrophic eventp drastically and nonselectively reduces size of population b. Founder effect - small no. of individuals colonize a new area Mutations Alter the nucleotide sequence of genes May give an selective advantage in a particular environment eg Tolerance to a toxic metaleg. Tolerance to a toxic metal
  5. 5. 8/21/2013 5 Gene Flow Movement of alleles form one population to another Pollen, seeds, fruits Runners or horizontal stemsRunners or horizontal stems Mating is random Individuals mate without regard to genotype Nonrandom mating Self fertilization- Self fertilization - Assortative mating- outcome of pollinator preference eg. Hawkmoths prefer to feed on flowers with long corolla tube Natural selection Thomas Malthus - Population of organisms tend to increase geometrically Geometric progression:- Geometric progression: 2,4,8,16,32,64… - Resources are limited Individual variation within species Mutation Crossing over Recombination TTransposons - DNA sequences - have the ability to move from place to place in chromosomes
  6. 6. 8/21/2013 6 Natural selection Individuals that are best adapted to their environment have the greatest chance of surviving and successfully reproducingp g
  7. 7. 8/21/2013 7 Certain traits that are common among individuals - provide superior adaptation in environmentenvironment Less common traits- do not confer selective advantage Tropical Forests Lack of wind Low light intensity Pl tPlants - Undivided leaves, large, with acumen Competition for resources is NOT necessary for natural selection to occur Natural selection may occur if certain individuals produce more offspring thanindividuals produce more offspring than others
  8. 8. 8/21/2013 8 Modes of natural selection Stabilizing selection - eliminates extreme phenotypes Directional selection - shifts the average or typical in one direction by favoring one of the extreme phenotypesy g p yp - leads to ANAGENESIS or phyletic evolution Diversifying selection - splits a population into 2 parts favoring both extremes of phenotypic range - leads to CLADOGENESIS or branching evolution Artificial selection Selectively breeding plants or animals to favor the production of offspring with desirable traits
  9. 9. 8/21/2013 9 Evolution can occur rapidly Punctuated equilibrium Eldredge and Gould, 1972 punctuated with short periods of rapid changechange Few year or thousand of years eg. -Colonization of mine tailings by plants Co-evolution a change in the genetic composition of one species in response to a genetic change in another Plants and insects Speciation Formation of new species from preexisting species Ultimate result of evolution Biological Species ConceptBiological Species Concept - A population whose members have the potential to interbreed with one another in nature to produce viable, fertile offspring but who cannot produce viable, fertile offspring with members of other species - Reproductively isolated from other populations Reproductive isolation Prezygotic - Sperm does not fertilize egg from other population No zygote is formed- No zygote is formed Postzygotic - Zygote or embryo does not survive or adult is infertile
  10. 10. 8/21/2013 10 Prezygotic Temporal isolation Seasonal Diurnal Ecological – eg. Acer black maple (Acer nigrum)- dry, high Cablack maple (Acer nigrum) dry, high Ca sugar maple (A. saccharum)- acidic Self fertilization Floral Behavioral- restriction to one pollinator Structural – white and red petaled flower Pollen-pistil incompatibility Post zygotic Inviable seed Hybrid inviability- not reach reproductive maturity Hybrid floral isolation – no pollinators Hybrid sterility Chromosomes do not pair during meiosis Brocolli (Brassica oleracea) x radish (Raphanus sativus) Raphanobrassica Hybrid breakdown- problems in later generation of hybrids Modes of speciation Allopatric speciation Geographical barrier that physically isolates populations hinders gene flow Sympatric speciationSympatric speciation Intrinsic factors alter gene flow Allopatric speciation geographical barriers: mountain range, oceans, lakes, creeping glaciers Adaptive radiation When a species move into previously- When a species move into previously unoccupied environment (island or occupied environment with many opportunities to succeed) - Scalesia spp. in Galapagos Islands
  11. 11. 8/21/2013 11 Sympatric Speciation Occurs within the range of parent populations Polyploidy - more than 2 complete sets ofp chromosomes; common in plants - oats, cotton, potatoes, tobacco, wheat a. Autopolyploid- from single species b. Allopolyploid- 2 different species - more vigorous than parents