Evolution with phylogeny


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Evolution with phylogeny

  1. 1. JJA Obico, Instructor, Department of Biology
  2. 2. Natural TheologyNatural Theology Philosophy dedicated top y discovering the Creator’s plan by studying nature Classify species in order to reveal the steps of life that God had createdcreated Carolus Linnaeus - sought to discover order in the diversity of life - founder of Taxonomy- founder of Taxonomy
  3. 3. Jean Baptiste LamarckJean Baptiste Lamarck In-charge of invertebrate collection at the Natural History Museum in Paris Compared current species to fossil formsfossil forms Use and DisuseUse and Disuse Inheritance of Acquired Characteristics
  4. 4. Biological EvolutionBiological Evolution Descent with modification Charles Darwin and Alfred WallaceCharles Darwin and Alfred Wallace Descent - Transfer of genetic material to offspring overtimeg p g a. Clonal reproduction (asexual) b. Sexual reproduction
  5. 5. Biological EvolutionBiological Evolution ModificationModification - Change in genetic material Mutation; genetic- Mutation; genetic recombination
  6. 6. What evolves?What evolves? Populationp - A group of individuals of the same species usually geographically delimited and i ll h i ifi ftypically have a significant amount of gene exchange Species - Consists of group generally intergrading- Consists of group generally intergrading, interbreeding populations that are reproductively isolated from other groups
  7. 7. Mechanisms of EvolutionMechanisms of Evolution Genetic DriftGenetic Drift Mutation Gene flowGene flow Non random mating Natural Selection
  8. 8. Population Genetics (PopGen)Population Genetics (PopGen) Study of behavior of genes in theStudy of behavior of genes in the population Genetics + EvolutionGenetics + Evolution Mendel (1866); Darwin and Wallace (1858)(1858)
  9. 9. Population GeneticsPopulation 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 T i d ?a. T inc; t dec? b. T dec; t inc? F d t hc. Freq does not change
  10. 10. Hardy-Weinberg EquilibriumHardy Weinberg Equilibrium Frequency of alleles will remain the sameFrequency of alleles will remain the same under the following conditions: 1 Size of population is large1. Size of population is large 2. No mutations 3 N i ti3. No migrations 4. Mating is random 5. Natural selection does not take place
  11. 11. Genetic DriftGenetic Drift - Change of frequency of alleles over timeChange of frequency of alleles over time due to chance a. Bottleneck effect - occurs when a catastrophic event drastically and nonselectively reduces size of population b. Founder effect - small no. of individuals colonize a new area
  12. 12. MutationsMutations Alter the nucleotide sequence of genesAlter the nucleotide sequence of genes May give an selective advantage in a particular environmentparticular environment eg. Tolerance to a toxic metal
  13. 13. Gene FlowGene Flow Movement of alleles form one populationMovement of alleles form one population to another Pollen seeds fruitsPollen, seeds, fruits Runners or horizontal stems
  14. 14. Mating is randomMating is random Individuals mate without regard toIndividuals mate without regard to genotype Nonrandom matingNonrandom mating - Self fertilization A t ti ti t f- Assortative mating- outcome of pollinator preference H k th f t f d fleg. Hawkmoths prefer to feed on flowers with long corolla tube
  15. 15. Natural selectionNatural selection Thomas MalthusThomas Malthus - Population of organisms tend to increase geometricallyincrease geometrically - Geometric progression: 2 4 8 16 32 642,4,8,16,32,64… - Resources are limited
  16. 16. Individual variation within species MutationMutation Crossing over RecombinationRecombination Transposons - DNA sequences - have the ability to move from place to place in chromosomes
  17. 17. Natural selectionNatural selection Individuals that are best adapted to theirIndividuals that are best adapted to their environment have the greatest chance of surviving and successfullyg y reproducing
  18. 18. Certain traits that are common amongCertain traits that are common among individuals - provide superior adaptation in- provide superior adaptation in environment Less common traits- do not conferLess common traits- do not confer selective advantage
  19. 19. Tropical ForestsTropical Forests Lack of windLack of wind Low light intensity Plants - Undivided leaves, large, with acumen
  20. 20. Competition for resources is NOTCompetition for resources is NOT necessary for natural selection to occur Natural selection may occur if certainNatural selection may occur if certain individuals produce more offspring than othersothers
  21. 21. Modes of natural selectionModes of natural selection Stabilizing selection - eliminates extreme phenotypesp yp Directional selection shifts the average or typical in one direction- shifts the average or typical in one direction by favoring one of the extreme phenotypes - leads to ANAGENESIS or phyletic evolution Diversifying selection - splits a population into 2 parts favoring both- splits a population into 2 parts favoring both extremes of phenotypic range - leads to CLADOGENESIS or branching evolutionevolution
  22. 22. Artificial selectionArtificial selection Selectively breeding plants or animals toSelectively breeding plants or animals to favor the production of offspring with desirable traits
  23. 23. Evolution can occur rapidlyEvolution can occur rapidly Punctuated equilibriumPunctuated equilibrium Eldredge and Gould, 1972 punctuated with short periods of rapidpunctuated with short periods of rapid change F th d fFew year or thousand of years eg. -Colonization of mine tailings by plants
  24. 24. Co-evolutionCo evolution a change in the genetica change in the genetic composition of one species in response to a genetic changep g g in another Plants and insectsPlants and insects
  25. 25. SpeciationSpeciation Formation of new species from preexistingp p g species Ultimate result of evolution Biological Species Concept A population whose members have the- A population whose members have the potential to interbreed with one another in nature to produce viable, fertile offspring but h t d i bl f til ff iwho cannot produce viable, fertile offspring with members of other species - Reproductively isolated from other populationsReproductively isolated from other populations
  26. 26. Reproductive isolationReproductive isolation PrezygoticPrezygotic - Sperm does not fertilize egg from other populationpopulation - No zygote is formed Postzygotic - Zygote or embryo does not survive or adult is infertile
  27. 27. PrezygoticPrezygotic Temporal isolationp Seasonal Diurnal Ecological eg AcerEcological – eg. Acer black maple (Acer nigrum)- dry, high Ca sugar maple (A. saccharum)- acidic Self fertilization Floral Behavioral restriction to one pollinatorBehavioral- restriction to one pollinator Structural – white and red petaled flower Pollen-pistil incompatibilityp p y
  28. 28. Post zygoticPost 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) p Hybrid breakdown- problems in later generation of hybrids
  29. 29. Modes of speciationModes of speciation Allopatric speciationAllopatric speciation Geographical barrier that physically isolates populations hinders gene flowp p g Sympatric speciation Intrinsic factors alter gene flowIntrinsic factors alter gene flow
  30. 30. Allopatric speciationAllopatric speciation geographical barriers: mountain rangegeographical barriers: mountain range, oceans, lakes, creeping glaciers Adaptive radiationAdaptive radiation - When a species move into previously unoccupied environment (island orunoccupied environment (island or occupied environment with many opportunities to succeed)opportunities to succeed) - Scalesia spp. in Galapagos Islands
  31. 31. Sympatric SpeciationSympatric Speciation Occurs within the range of parentOccurs within the range of parent populations Polyploidyyp y - more than 2 complete sets of chromosomes; common in plants - oats, cotton, potatoes, tobacco, wheat a. Autopolyploid- from single species b. Allopolyploid- 2 different species - more vigorous than parentsg p
  32. 32. What is phylogeny? Evolutionary history or pattern of descent What is phylogenetic systematics (cladistics)?(cladistics)? Branch of systematics concerned with inferring phylogenyphylogeny Lines on cladogram? Lineage = sequence of ancestral-descendentLineage sequence of ancestral descendent populations through time; represent descent
  33. 33. Split, from one lineage into two? Divergence, which may lead to speciation Pre-existing feature?g Primitive / Ancestral / Plesiomorphic New feature?New feature? Advanced / Derived / Apomorphic
  34. 34. PheneticPhenetic - classification based on overall similaritiessimilarities - common to everyone Phylogenetic classification based on evolutionary- classification based on evolutionary history or pattern of descent
  35. 35. Can be arbitraryCan be arbitrary, e.g., classify these:
  36. 36. Represented in the form of a cladogram/Represented in the form of a cladogram/ phylogenetic tree CladogramCladogram • Lines- lineage or clades; denote descent • Branching- divergence from a common ancestorBranching divergence from a common ancestor Evolution recognized as a change from pre-existing character state(ancestral) topre existing character state(ancestral) to a new (derived) character state
  37. 37. All of life is interconnected byAll of life is interconnected by TAXA descentdescent A B C D E F TIME lineage or clade TIME Cladogram or Phylogenetic TreeCladogram or Phylogenetic Tree
  38. 38. A B C D E F TAXA TIME speciation Cladogram or Phylogenetic Tree
  39. 39. CladisticsCladistics Methodology of inferring the pattern of evolutionary history of a group ofevolutionary history of a group of organisms using apomorphic characters Ancestral character Pleisiomorphy- Pleisiomorphy Derived character - Apomorphy- Apomorphy
  40. 40. Apomorphies the result of evolutionApomorphies - the result of evolution. Taxa sharing apomorphies underwentTaxa sharing apomorphies underwent same evolutionary history, should be grouped togethershould be grouped together.
  41. 41. A B C D E F TAXA Apomorphies f B&C Apomorphy for taxon D for taxa B&C TIME Apomorphy for taxa B-F Cladogram or Phylogenetic Tree
  42. 42. Common ancestry TAXA A B C D E F TIME common ancestor (of taxon D, E, & F) Cl d Ph l ti T common ancestor (of taxon A & taxa B-F) Cladogram or Phylogenetic Tree
  43. 43. Similarity due to common ancestry- similar DNA sequences Intraindividual homology?gy Similarity by common ancestry of features within an individual e g carpels and leavesan individual, e.g., carpels and leaves (common ancestry by genes)
  44. 44. Similarity not by common ancestry. Types? Convergence independent evolution of aConvergence - independent evolution of a similar feature in 2 or more lineages. Reversal - loss of a derived feature with re- establishment of ancestral featureestablishment of ancestral feature.
  45. 45. Convergence - Stem succulence and “spines” in Cactaceae and Euphorbia sppCactaceae and Euphorbia spp.
  46. 46. Reversal - Loss of perianth in Lemna, Wolffia.
  47. 47. Recognized group in phylogeneticRecognized group in phylogenetic systematics Consisting of a common ancestor plus allConsisting of a common ancestor plus all of its descendants Sequential listing of monophyletic groupSequential listing of monophyletic group - serve as a phylogenetic classification schemescheme
  48. 48. A B C D E F TAXA monophyletic group TIME t common ancestor (of taxon A & taxa B-F) common ancestor (of taxon D, E, & F) Cladogram or Phylogenetic Tree
  49. 49. Consisting of a common ancestor but notConsisting of a common ancestor but not all descendants of that common ancestor Two or more separate groups each with a separate common ancestor
  50. 50. A B C D E F TAXA TIME common ancestor (of taxon A & taxa B-F) common ancestor (of taxon D, E, & F) Cladogram or Phylogenetic Tree
  51. 51. A B C D E F TAXA A B C D E F TIME common ancestor ( f t A & t B F) common ancestor (of taxon D, E, & F) Cladogram or Phylogenetic Tree (of taxon A & taxa B-F)