Modern theory and more

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1 In this lecture topic Major events in the history of Biology: Modern Theory and more p 2 +2pq+q 2 = 1 1 What is a species and how do new species arise? The importance of systematics? How can Mendelian genetics be use to explain natural selection in populations? Allele frequencies and evolution Hardy- Weinberg. Sources of variations in alleles. 2 Darwin s five theories No constancy of species Common ancestry Gradual changes Natural selection (microevolution) Multiplication of species Speciation 3 4 Species concepts what is a species? Species concepts Morphospecies Biological species Morphospecies Phylogenetic species Species are groups of actually or potentially interbreeding populations, which are reproductively isolated from other such groups. Ernst Mayer (1942) Mayer ( ) Yellow throated warbler Yellow rumped warbler 5 Figure Page 1

2 Rate of evolutionary change Anagenesis Cladogenesis Sp. A Sp. B Sp. C Sp. D Species concepts Ring species Parapatric Elaphe oboleta Figure Black rat snake E. o. osoleta Time Yellow rat snake E. o. quadrivittato A B C Phenotype 7 Texas rat snake E. o. lindeimeri Gray rat snake E. o. spiloides Everglades rat snake E. o. rossalleni 8 Species concepts Ring species Parapatric Ensatina eschscholtzi Figure Video Painted salamander E. e. picta Yellow-eyed salamander E. e. xanthoptica Oregon salamander E. e. oregonensis Sierra Nevada salamander E. e. platensis Yellow-blotched salamander E. e. croceater Second contact Hybridization outcomes Fusion of the populations Reinforcement Hybrid zone formation Extinction of one population Creation of a new species Monterey salamander E. e. eschscholtzii Large-blotched salamander E. e. klauberi 9 10 Allopatric Speciation - Vicariance Allopatric Speciation - Dispersal A B C D A B C D A 3. C A 4. C D D B B Figure Figure Page 2

3 Grylloblattid Ice age vicariance Sympatric speciation Nonnative species Native species Nonnative species Native species Video Biological species Reproductive isolation Biological species Reproductive isolation Prezygotic isolation Habitat (Ecological) Temporal Behaviour Mechanical Gametic Postzygotic isolation Prezygotic isolation Habitat (Ecological) Temporal Behaviour Mechanical Gametic Postzygotic isolation Biological species Reproductive isolation Biological species Reproductive isolation Prezygotic isolation Habitat Temporal Behaviour Mechanical comit orchid Gametic Postzygotic isolation Prezygotic isolation Habitat (Ecological) Temporal Behaviour Mechanical Gametic Postzygotic isolation Page 3

4 Biological species Reproductive isolation Important stages in the history of Biology 20th century: Modern biology Prezygotic isolation Postzygotic isolation Hybrid inviability Hybrid sterility Hybrid breakdown Cellular respiration, ATP and mitochondia ( ) Ecology (1940 s) DNA is the genetic materials (1943) DNA structure (1953) Gene regulation (1961) Genetic code (1960 s) Recombinant DNA experiments (1970 s) Cloning of a mammal (1997) Human genome sequence (2000) Types of taxonomies Phylogenetic tree Folk Artificial Mechanical Natural (Evolutionary) Cladistic (Phylogenetic) Hennig ( ) 21 Figure 18.13a 22 Cladogram Conflicting interpretations Figure 18.13b Page 4

5 Conflicting interpretations Hylabatidae Hyobates (Gibbon) Pongo (orangutan) Pongidae Gorilla Pan (chimpanzee) Hominidae Homo (human) Cladistics - Useful terms Apomorphies Derived characters within a group (evolutionary lineage) Plesiomorphies Primitive characters within a group Synapomorphies Derived characters shared between groups Symplesiomorphies Shared primitive characters that are shared between groups Cladistics Useful terms A AB ACD AC ACE A= Symplesiomorphy C= Synapomorphy C= Apomorphy E= Autapomorphy A= Plesiomorphy Cladogram construction Double jointed mandible Two pairs of wings Folding wing mechanism Metamorphosis Reduction of wings to haltere Cladogram construction Cladogram construction Double jointed mandible Two pairs of wings Folding wing mechanism Metamorphosis Reduction of wings to haltere Double jointed mandible Two pairs of wings Folding wing mechanism Metamorphosis Reduction of wings to haltere Page 5

6 Cladogram construction Cladogram construction Double jointed mandible Two pairs of wings Folding wing mechanism Metamorphosis Reduction of wings to haltere Double jointed mandible Two pairs of wings Folding wing mechanism Metamorphosis Reduction of wings to haltere Cladogram construction Cladogram construction A B C D E Double jointed mandible Two pairs of wings Folding wing mechanism Metamorphosis Reduction of wings to haltere 33 C B A D E A - Double jointed mandible B - Two pairs of wings C - Folding wing mechanism D - Metamorphosis E - Reduction of wings to haltere 34 Parsimony The KISS principle Homology vs. homoplasy The camera eye Octopus Fish Figure Page 6

7 Homology vs. homoplasy The camera eye Octopus Fish Anatomy of a Cladogram Monophyletic Polyphyletic Paraphyletic 37 Figure Porifera Cnidaria Bryozoa Platyhelminthes Nematod Mollusca Annelida Onychophora Arthropoda Echinodermata Chordata Green algae Liverworts Hornworts Mosses Lycophytes Pterophytes Gymnosperms Angiosperms Lophophore Trochophore Moulting Lophotrohozoa Ecdysozoa Spiral, blastopore mouth, schizocoel Radial, blastopore mouth, enterocoel No tissues Diploblastic, radial Tissues Triploblastic, bilateral Phylogeny of animals (Fig 26.6) 39 Phylogeny of plants Figure In this lecture topic Major events in the history of Biology: Modern Theory and more p 2 +2pq+q 2 = 1 41 What is a species and how do new species arise? The importance of systematics? How can Mendelian genetics be use to explain natural selection in populations? Allele frequencies and evolution Hardy- Weinberg. Sources of variations in alleles. 42 Page 7

8 Darwin s five theories Important stages in the history of Biology Modern theory and more No constancy of species Common ancestry Gradual changes Natural selection (microevolution) Multiplication of species Synthetic (Modern) theory of evolution Population genetics and natural selection based on Mendelian genetics 43 Huxley ( ) 44 Microevolution Evolutionary changes that result from changes in allele frequencies in a population, or in chromosome structure or numbers due to mutation and recombination. Some basic terms for microevolution Allele Phenotype Genotype Dominant and recessive Important stages in the history of Biology Modern theory and more Punnett squares Hardy ( ) Weinberg ( ) 47 3:1 9:3:3:1 48 Page 8

9 Incomplete dominance snap dragons Genotype and allele frequencies P - parental F 1 Generation1 F 2 Generation2 Phenotype Genotype Number Genotype frequency Total C R alleles Total C W alleles C R C R Red X X C R C R = 25% C R C R 450 C R C w /1000 = /1000 = x450 = 900 1x500 = 500 0X450 = 0 1x500 = 500 C w C R Pink C W C W White C w C R = 50% C W C W = 25% Figure C W C W 50 Total /1000 = = 1.0 0x50 = p = 0.7 2x50 = q = Using the Hardy-Weinberg Principle Hardy-Weinberg principle s assumptions p 2 +2pq+q 2 = 1 C R frequency p=0.7 C W frequency q=0.3 C R frequency p=0.7 C R C R = p 2 C W frequency q=0.3 C R C W = pq No natural selection Random mating sexual selection population is large Gene flow No mutation C w C R = pq C W C W = q Effect of selection Effect of selection - fixation Distance run Average speed Revolutions / day Revolutions / minute Generation Generation Figure Page 9

10 Effect of selection against recessive Effect of selection for heterozygote Effect of selection for heterozygote Selection with multiple loci traits (Quantitative traits) Figure 10-1 Number of individuals Figure Measurement or value of the trait Selection with multiple loci traits Directional selection Selection with multiple loci traits Stabilizing selection Before selection After selection Before selection After selection Figure 17.9a 59 Figure 17.9b 60 Page 10

11 Selection with multiple loci traits goldenrod galls Selection with multiple loci traits Stabilizing selection Goldenrod galls % fly larvae killed % fly larvae killed Wasps Birds % fly larvae alive or killed Gall diameter (mm) Before selection After selection Gall diameter (mm) 61 Figure Selection with multiple loci traits Disruptive selection Selection with multiple loci traits Disruptive selection Before selection After selection Figure 17.9c 63 Figure 25-5b 64 Hardy-Weinberg principle s assumptions No natural selection Random mating sexual selection population is large Gene flow No mutation Nonrandom mating - Inbreeding Generation 1 Generation 2 Homozygote parent for A 1 Eggs A 1 A 1 Homozygote Heterozygote parent Eggs A 1 A 2 Heterozygote Homozygote parent for A 2 Eggs A 2 A 2 Homozygote Generation 3 65 Generation 4 Figure Page 11

12 Nonrandom mating - Sexual dimorphism Females Beetle Scarlet tanager Lion Nonrandom mating - sexual selection Sexual selection On males female choice On males competition Combat Infanticide Males Sexual selection female choice riflebird Tail feathers Sexual selection Male competition - combat Mean number of mates/male Seals V1 Seals V2 Shortened Normal Lengthened Sexual selection Male competition - combat Sexual selection Male competition Copulatory wheel Page 12

13 Sexual selection Male competition infanticide Hardy-Weinberg principle s assumptions No natural selection Random mating sexual selection population is large Gene flow No mutation Genetic drift Genetic drift bottle neck affect Figure 25-6 Genetic drift Founder affect Hardy-Weinberg principle s assumptions No natural selection Random mating sexual selection population is large Gene flow No mutation Page 13

14 Gene flow - migration Source population New population Source population New population Gene flow migration Seed Gene flow A A 1A A 1A 1 A 1A 1 1 A 1A A A 1A 2 A 1A 1 A 1A 2 A 1A 2 A 1A A 1A A 1A 1 1A 2 A 1A 1 A1A 2 1A 2 A 1A 1 Frequency of A 1 = 0.90 Frequency of A 1 = 0.50 Frequency of A 2 = 0.10 Frequency of A 2 = 0.50 Frequency of A 1 = 0.83 Frequency of A 1 = 0.67 Frequency of A 2 = 0.17 Frequency of A 2 = 0.33 Figure 25-8b Hardy-Weinberg principle s assumptions No natural selection Random mating sexual selection population is large Gene flow No mutation Eukaryote variability - Random segregation Chromosomes Combinations Chromosomes Combinations ,554, cow 1,073,741, ,359,738, x , x mouse 1,048, x human* 4,194, Mutation Beneficial Neutral Deleterious Genetic code Figure Figure Page 14

15 Mutation Silent Point mutations Silent Missense Nonsense Frame shift Chromosomal mutations Missense Mutation sickle cell Normal: the one big fly had one red eye Figure 10-1 Missense: thr one big fly had one red eye. Figure Nonsense Frame shift Normal: the one big fly had one red eye Normal: the one big fly had one red eye Nonsense: the one big Frame shift: the one rbi gfl yha don ere dey Page 15

16 Mutation Inversion Figure Mutation Deletion Figure Point mutations Chromosomal mutations Inversions Translocation Deletion Duplication Crossing over Polyploidy Genome duplication Translocation Point mutations Chromosomal mutations Inversions Translocation Duplication Deletion Crossing over Polyploidy Genome duplication Duplication Chromosomal mutations crossing over Polyploidy and speciation Autopolyploid Meiosis 2n = 6 4n = 12 Figure Figure Polyploidy and speciation Allopolyploid Species A 2n = 6 Meiosis Meiosis Species B 2n = 6 Gametes n = 3 Fertilization Gametes n = 3 Interspecific Species 2n = 6 Mitosis 2n = 14 Meiosis Meiosis Diploid gametes n = 6 Selffertilization Selffertilization Diploid gametes n = 6 Figure Tetraploid zygote n = Polyploidy and speciation Allopolyploid Triticum monococcum (einkorn) Unknown wild wheat Sterile hybrid Triticum turgidum (emmer) Triticum tauschii Triticum aestivum (bread wheat) 14AA X 14BB 14AB 28AABB x 14DD 42AABBDD Figure Page 16