1 / 51

Evolution

Evolution. Precursors to Darwin. Jean Baptiste de Lamarck Evolutionary change proceeds via inheritance of acquired characteristics ie. Giraffe’s ancestors stretched their necks and subsequent generations inherited longer necks

yates
Télécharger la présentation

Evolution

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Evolution

  2. Precursors to Darwin • Jean Baptiste de Lamarck • Evolutionary change proceeds via inheritance of acquired characteristics • ie. Giraffe’s ancestors stretched their necks and subsequent generations inherited longer necks • ie. Loss of a digit would result in loss or reduction of digit in subsequent generations

  3. Precursors to Darwin • Incorrectness of Lamark’s hypothesis • Somatic changes do not alter the genes passed on to offspring • ie. The loss of a digit does not remove the dna from the genome that specifies development of a digit.

  4. Precursors to Darwin • Charles Lyell • Geologist who first explained the significance of geological formations/strata • Realized that geological changes must require great time spans • Formulated uniformitarianism • Physical and chemical processes are the same now as they have always been • Natural processes occurring now, have always occurred

  5. Darwin’s Synthesis • Five Tenets • Perpetual change (derived from Lyell’s work) • Common descent (derived from observations from Beagle and other journeys) • Multiplication of species (corollary to common descent) • Gradualism (derived from Lyell and lack of any other mechanism) • Natural selection (Darwin’s most original contribution)

  6. Mechanism of Darwinian Natural Selection 1. Variation exists in the population

  7. DIVERSITY EXISTS WITHIN POPULATIONS Homo sapiens subgraduensis

  8. Mechanism of Darwinian Natural Selection 1. Variation exists in the population 2. Competition for survival, most animals die before reproducing

  9. Competition for Survival

  10. Mechanism of Darwinian Natural Selection 1. Variation exists in the population 2. Competition for survival, most animals die before reproducing 3. Survival of those most fit for the environment

  11. DEATH IS NOT RANDOM; IT IS SELECTIVE Changes in finch beak morphology during drought of 1976/1977

  12. Mechanism of Darwinian Natural Selection 1. Variation exists in the population 2. Competition for survival, most animals die before reproducing 3. Survival of those most fit for the environment 4. Offspring are from the survivors 5. Offspring inherit the genes that made their parents fit for the environment.

  13. THE MODERN SYNTHESIS “Evolution is a change in the genetic composition of populations. The study of the mechanisms of evolution falls within the province of population genetics.” --Theodosius Dobzhansky. 1951

  14. CHARLES DARWIN ON THE ORIGIN OF SPECIES 1859 “Community of embryonic structure reveals community of descent.” “Embryology rises greatly in interest, when we look at the embryo as a picture, more or less obscured, of the progenitor, either in its class or larval state, of all the members of the same great class.” The embryos of the organisms in a phylum reflect the evolutionary progenitor of that phylum

  15. HOMOLOGY “The same organ in all its varieties of form” Serial Homology Derived forms within the same organism Special Homology Derived forms between different species Versus ANALOGY Sir Richard Owen Forms similar due to same function

  16. KARL ERNST von BAER: “The general features of a large group of animals appear earlier in development than do the specialized features of a smaller group…The early embryo is never like a lower animal, but only like its early embryo.”

  17. DARWIN (1874): “Thus, if we may rely on embryology, ever the safest guide in classification, it seems that we have at last gained a clue to the source whence the Vertebrata were derived.” AGGASIZ (1874): “One could hardly open a scientific Journal or any popular essay onNatural History without meeting some allusion to the Ascidians as our ancestors.”

  18. CLADOGRAM ( partial) of VERTEBRATES: DESCENT WITH MODIFICATION

  19. THE DEMISE of EVOLUTIONARY MORPHOLOGY… “It is difficult, even if possible, to say whether the differences or the resemblances have a greater zoological value (because we have no clearly defined standard of zoological value).” -A. Sedgwick, 1894. …AND THE EXODUS TO GENETICS "Morphology having been explored in its minutest corners, we turned elsewhere...The geneticist is the successor of the morphologist." -W. Bateson, 1894

  20. INDEPENDENT EVIDENCE for COMMON DESCENT: Biological genetic documentation

  21. GENETIC EVIDENCE for DESCENT WTH MODIFICATION MOLECULAR SYNAPOMORPHIES Phylogenetic tree made from interspersed DNA elements. Four transposon insertions, at loci 4-7, define a clade of whales and hippos.

  22. FRANÇOIS JACOB: EVOLUTION AS TINKERING with REGULATORY GENES in the EMBRYO “Small changes modifying the distribution in time and space of the same structures are sufficient to affect deeply the form, the functioning, and the behavior of the final product--the adult animal. It is always a matter of using the same elements, of adjusting them here or there, of arranging various combinations to produce new objects of increasing complexity. It is always a matter of tinkering.”

  23. RICHARD B. GOLDSCHMIDT: Evolution consists of inherited changes of development Functional biology = anatomy, gene expression Development =d[Functional biology]/dt Evolution = d[Development]/dt

  24. PAX6/Eyeless Expression in Insect and Mouse Eye Primordia

  25. HOMOLOGOUS GENES for ANALOGOUS TRAITS Mouse Pax 6 instructs fly compound eye formation in antenna

  26. HOMOLOGOUS HOX GENES: DERIVATION

  27. HOMOLOGOUS HOX GENES: EXPRESSION

  28. MUTATIONS IN REGULATORY GENES CAN GIVE THE PROTEINS NEW PROPERTIES: UBX ACQUIRES THE ABILITY to REPRESS DISTAL-LESS in the INSECT CLADE R. Galant and S. B. Carroll, 2002. Nature 415:910. Ronschaugen, M. et al. 2002. Nature 415: 914. .

  29. HOW THE DUCK GOT ITS WEBBED FEET Merino et al., 1999. Dev. Biol. 200: 35 - 45. Chick Hindlimb Duck Hindlimb Gremlin Apoptosis Newborn BMP

  30. HOW THE DUCK GOT ITS WEBBED FEET. II. Experimental Manipulation of Chick Feet Chick Hindlimb Treated with Gremlin-Containing Bead in Interdigital Space Untreated Chick Hindlimb

  31. ORIGIN OF FEATHERS FROM SCALES Through Repetition of SHH-BMP Interactions (Harris, M., et al., 2002)

  32. Developmental Mechanisms for Phylogeny Shigeru Kuratani et al. 2001. Phil. Trans. Roy. Soc. London B 356: 1615-1632

  33. Tenets of Evolutionary Theory • Perpetual change • Common descent • Multiplication of species • Punctuated equilibrium • Natural selection

  34. Perpetual Change – The Fossil Record Burgess Shale Fossils, Canada Dinosaur Provincial Park, Canada

  35. 1.6 MYA 3.4 million years – 3.4 million generations 5 MYA 19 million years – 19 million generations 24 MYA 13 million years – 13 million generations 37 MYA 21 million years – 21 million generations 58 MYA Common Descent

  36. Homologies

  37. Phylogenies • Shared traits – synapomorphies • Homologous structures • Anatomical • Genetic • Ratite birds skeletal homologies • Those homologies present in the most groups are most ancestral • Those in few or one define species

  38. GENETIC EVIDENCE for DESCENT WTH MODIFICATION MOLECULAR SYNAPOMORPHIES Phylogenetic tree made from interspersed DNA elements. Four transposon insertions, at loci 4-7, define a clade of whales and hippos.

  39. Ontological Homologies • Homologies of embryonic structures and developmental patterns • Vertebrate embryos • Pharyngeal arches • Somites • Segmentation of CNS • Subtle changes in developmental expression of genes can drastically alter morphologies • Speciation and phylogenic event

  40. Multiplication of Species

  41. Subcomponents of Evolutionary Theory • Microevolution • Genetic change • Macroevolution • Major events

  42. Microevolution • Genetic variation • Alleles – different versions of genes • Polymorphism – degree of variation in alleles • Allele frequencies – occurrence of allele variety • Changes in allele frequencies due to • Genetic drift • Non-random mating • Migration • Natural selection processes

  43. Microevolution – Genetic Drift • Random fluctuation in allele frequencies • Dramatic changes in genetic variation within a population or species Greater affect on small populations – they have less inherent variation to start with

  44. Microevolution – Nonrandom Mating • Individuals with a particular genotype mate preferentially with individuals of the same genotype • Result – their common alleles become more frequent within the resulting population

  45. Microevolution - Migration • Influx – efflux of individuals with a particular genotype into a population increase/decreases frequency of their alleles

  46. Microevolution – Natural Selection • Environmental factors select for particular phenotypes and their underlying genotypes • Alleles that give rise to selected phenotype increase in frequency in population

  47. Natural Selection • Environmental conditions provide a selective pressure • Alleles producing selected phenotype increase in population • Disruptive selection is a strong speciation event

More Related