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Evidences of Evolution • 1. Fossils • 2. Comparative Morphology – Bessey’s Dicta Homologous Structures Derived From Leaves Evidences of Evolution • 1. Fossils • 2. Comparative Morphology – Bessey’s Dicta Evidences of Evolution • 1. Fossils • 2. Comparative Morphology – Bessey’s Dicta Evidences of Evolution • 1. Fossils • 2. Comparative Morphology – Bessey’s Dicta • 3. Comparative Physiology – C3, C4, CAM Evidences of Evolution • 1. Fossils • 2. Comparative Morphology – Bessey’s Dicta • 3. Comparative Physiology – C3, C4, CAM • 4. Biochemistry – proteins and DNA Evidences of Evolution • (micromolecules) flavinoides – • 1. Fossils • 2. Comparative Morphology – Bessey’s Dicta • 3. Comparative Physiology – C3, C4, CAM • 4. Biochemistry – proteins and DNA (macromolecules) anthocyanin/ betalains - (10 fams) = Caryophyllales Evidences of Evolution • 1. Fossils • 5. Vestigial Organs – staminoids • 2. Comparative Morphology – Bessey’s Dicta • 3. Comparative Physiology – C3, C4, CAM • 4. Biochemistry – proteins and DNA Evidences of Evolution • 1. Fossils • 5. Vestigial Organs – staminoids • 2. Comparative Morphology – Bessey’s Dicta • 3. Comparative Physiology – C3, C4, CAM • 4. Biochemistry – proteins and DNA • 6. Geographical Distribution – Continental Drift Continents during Creataceous 100 mya Geographically Separated, Morphologically Similar • Plantanus occidentalis Plantanus hispanica Evidences of Evolution • 1. Fossils • 5. Vestigial Organs – staminoids • 2. Comparative Morphology – Bessey’s Dicta • 3. Comparative Physiology – C3, C4, CAM • 4. Biochemistry – proteins and DNA • 6. Geographical Distribution – Continental Drift • 7. Development - Evidences of Evolution • 1. Fossils • 5. Vestigial Organs – staminoids • 2. Comparative Morphology – Bessey’s Dicta • 3. Comparative Physiology – C3, C4, CAM • 6. Geographical Distribution – Continental Drift • 7. Development - • 4. Biochemistry – proteins and DNA • 8. Selective Breeding – Brassica Carboniferous Period 300 mya Kingdom: Plantae • 1. Waxy Cuticle • 2. Gametangia – archegonia, antheridia • 3. Embryos • 4. Pigments • 5. Thick spore walls – homosporous heterosporous Evolution from Green Algae to Plants Nontracheophytes vs. Tracheophytes • Tracheophytes have vascular tissue. – Xylem • tracheids • vessel elements – Phloem • seive tubes • comapion cells First Tracheophytes (vascular plants): Division: Rhyniophyta Rhynia Cooksinia–M. Silurian 420 mya • Rhynia – L. Devonian 360 mya Phylum: Sphenophyta Horsetails Phylum:Cycadophyta cycads Phylum:Ginkgophyta ginkgo Phylum:Gnetophyta Welwitchia Phylum:Coniferophyta conifers Phylum: Anthophyta flowering plants Charles Darwin 19thC Charles Darwin 19thC Acquired Characteristics vs. Natural Selection • Acquired characteristics – J. B. Lamarck • Natural Selection – C. Darwin – A. Wallace Darwin’s Tenets • 1. Many more individuals are born than will survive. • 2. There is variation among individuals. • 3. Individuals with certain characteristics have a better chance of survival and reproducing than individuals with other characteristics. • 4. At least some of the characteristics resulting in differential reproduction are heritable. • 5. Enormous spans of time are available for slow, gradual change. Species?? • Groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups. – Ernst Mayr Harvard 1940 Evolutionary Divergence Evolutionary Divergence Evolutionary Divergence Allopatric Speciation • Allopatric Speciation Phylogenetic Hierarchy • Kingdom – Division (Phylum) • Class – Order » Family » Genus » species Isolating Mechanisms for Species (Character Displacement) • 1. Mechanical (Reproductive) Isolation – flower structure – Aquilegia canadensis – A. formosa – A. ecalcarota – Asclepias • 2. Habitat Isolation – Plantanus occidentalis – P. orientalis – P. acerifolia • 3. Seasonal Isolation – Pinus radiata Feb. – P. muricata April Enhancement of Cross-pollination (within species) • 4. Mechanical • 5. Chemical Form an occasional variation within a species • Scarlet Gilia – Red, Yellow Variety • Chestnut Oak – var. accumata, var. prinoides Population Genetics • Alleles - color in scarlet gilia – RED (R) dominant – Yellow (r) recessive Hardy - Weinberg Equilibrium • Gene frequencies in a population will not change if: • 1. No plant has an adaptive advantage. • 2. No immigration or emigration. • 3. No mutations. Difficulties in interpreting Evolutionary Change • Convergence - polyphyletic – Cactaceae, Euphorbiaceae • -----------------------------------------• Divergent - monophyletic – Lamiaceae, Verbenaceae Interpreting Evolutionary Change • 1. Vegetative characteristics are more liable to evolutionary change. (Also have a high degree of “genetic plasticity”.) • 2. Reproductive characteristics are most conservative and are best for determining the evolution of taxa. • “Good Characteristic” - heritable and not affected much by the environment. Interpreting Evolutionary Change Bessey’s Dicta 1. Woody plants came before herbs. 2. Perennials before biennials or annuals. 3. Alternate leaves are primitive; opposite or whorled are advanced. 4. Bisexual flowers are primitive. 5. Many parted spirally arranged flowers are primitive to all other arrangements. Bessey’s Dicta 5. Many parted spirally arranged flowers are primitive to all other arrangements. 6. Hypogyny is primitive to epigyny and perigyny. 7. Numerous separate carpels are primitive to fewer fused carpels. Bessey’s Dicta 8. Pollen grains with 1 pore preceded those with 1 or more pores. 9. Axile placentation preceded free central placentation. 10. Single fruits preceded aggregate fruits formed from several ovaries. 11. The capsule preceded the drupe or berry. Mechanisms for Evolutionary Change • 1. Gene Mutations – changes in sections of the DNA on chromosomes (rare) • 2. Chromosomal Mutations – the normal (2n) chromosome number is not maintained – POLYPLOIDY • 40% - 70% of plant species • Autopolyplody POLYPLOIDY • mint species - Europe – Galeopsis pubsescens 2n = 16 (8 prs.) – Galeopsis speciosa 2n = 16 (8 prs.) POLYPLOIDY • mint species - Europe – Galeopsis pubsescens 2n = 16 (8 prs.) – Galeopsis speciosa 2n = 16 (8 prs.) – ALLOPOLYPLOID • doubling of chromosome no. in 2 different species – Galeopsis pubescens X speciosa 4n = 32 • artificial hybrid – Galeopsis tetrahit 4n = 32 • natural species (one step evolution) POLYPLOIDY – – – – Modern Speciation Spartina pectinata 2n = 62 USA Spartina townsedii 2n = 60 Europe Spartina pectinata X townsendii (4n) = 122 England 1870 sterile Spartina anglica (4n) 2n = 122 England 1890 fertile • Allopolyploidy • Sympatric Speciation - no geographical barrier POLYPLOIDY • Tragopogon Salsiflies, Goatsbeards – T. porrifolius – T. dubius – T. pratensis • Allopolyploids: Sympatric Speciation – T. miscellus 4n • T. pratensis X dubius (chloroplasts) – T. mirus • T. pratensis X porrifolius • Allopolyploids more common than diploids today. Polyploids • Diploids vs. • Polyploids POLYPLOIDY – Raphanus (radish) X Brassica (cabbage) --> 4n tetraploid – 2n 2n 3. Reshuffling or Recombination of Existing Genes • Normal Diploid Condition (2n) • Homologous Pairs • Crossing over - Arboreous (A), Fruticose (a) • L. leaves (L), S. leaves (l) • A a • L l 3. Reshuffling or Recombination of Existing Genes • Normal Diploid Condition (2n) • Homologous Pairs • Crossing over - Arboreous (A), Fruticose (a) • L. leaves (L), S. leaves (l) • a A • L l 3. Reshuffling or Recombination of Existing Genes • Random Assortment – how the different chromosomes combine in gametes • Fertilization – the many different combinations in eggs and sperm combine Modern Theory of Organic Evolution • 1. There is a tremendous amount of variability in the gene pool of each organism (each species). • 2. Organisms have changed through time. • 3. Evolutionary change is directed by natural selection. Evolutionary Change • A change in the gene frequency of a gene in a gene pool. • If an organism is incapable of changing as the environment changes? • EXTINCTION Classification Theories (Attempts to Determine “Natural Groupings”) • Traditional Taxonomy, Traditionalists – Are not opposed to making value judgments (weighted characteristics) in construction phylogenetic trees. Use para and polyphylogeny • Phylogenetic Taxonomy, Cladists – Use only objective data when constructing monophyletic evolutionary trees. Also use computers and numerical comparison of unweighted characteristics for cladograms.
