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Vertebrate Zoology

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  1. Vertebrate Zoology Dr. A. Kristopher Lappin is attending themeeting of the Society for Comparative and Integrative Biology (Seattle, WA). He will return Friday, January 8. Dr. Moriarty, Biological Sciences Dept.Biostatistics, Population and Community Ecology, Ornithology

  2. Vertebrate Zoology • Introduction: Dr. A. Kristopher Lappin • Blackboard Site • Lecture & Lab • check regularly (also Cal Poly e-mail) • PP presentations, notes, lab assignments, etc. posted there but not handed out • Language / Vertebrate Zoology Analogy • Principles of Evolution

  3. Goals of Course • to develop of basic understanding of the evolution, diversity, anatomy, physiology, behavior, ecology, & natural history of vertebrates • to gain an appreciation for vertebrate life • to develop an ability to share your appreciation & knowledge of vertebrates w/ others during this critical time in human history

  4. Definitions of Biological Disciplines • evolution—change through time • biodiversity—variety of living forms & their habits • anatomy & physiology—structure & function • behavior—how animals do things • ecology—interactions of animals w/ each other & their physical environments

  5. Some Biological Levels of Organization • how molecules w/in cells interact—molecular biology • how cells function—cell biology • how tissues/organs of an individual organism function & interact—physiology

  6. Some Biological Levels of Organization • how individuals w/in a species interact—population biology • intraspecific level • how different kinds of organisms interact—community ecology • interspecific level • Relate levels of organization when comparing organisms to better understand evolutionary trends.

  7. What is a theory? • hypothesis / set of hypotheses that provide a powerful explanation for a variety of related phenomena & are supported by overwhelming evidence • purpose is to guide scientific inquiry • Gravity is a theory. • Evolution is a theory.

  8. Theory of Evolution • establishment of Evolution as a scientific theory • Charles Robert Darwin • Alfred Russel Wallace • developed theory of natural selection independently • Darwin published “On the Origin of Species” (1859)

  9. Influences on Darwin • Lamark • first scientific explanation of evolution • “inheritance of acquired characteristics” • made case that fossils are remains of extinct animals • Lyell • uniformitarianism—same physical laws & geological processes operate now as during Earth’s history

  10. Influences on Darwin • voyage of the H.M.S. Beagle • Darwin 23 years old • 5-year voyage around the world

  11. Influences on Darwin • observed & collected fauna & flora • found fossils • found seashells in mountains at 4,000 meters • experienced major earthquake in S. America

  12. Influences on Darwin • Beagle stopped at the Galapagos Islands (on equator 600 miles off of W coast of S. America) • spent 5 weeks on islands

  13. Influences on Darwin • Galapagos visit hugely influential on Darwin’s development of theory of evolution • organisms unique, yet similar to continental forms in S. America (e.g., giant tortoises due to lack of predators)

  14. Perpetual Change & Geological Time • Perpetual geological & biological change is the rule. • Consider the vastness of geological time. • radiometric dating • age of Earth—4.6 billion years

  15. Evidence of Perpetual Change Banded Iron Formation, Australia • rocks up to 3 billion years old

  16. Evidence of Perpetual Change Big Island, Hawaii • oldest part of island 400,000 years old (7,500 times younger than the old rocks)

  17. Fossil Record • oldest microscopic fossils—3.5 billion years • oldest macroscopic fossils—650 million years • most animal phyla present 540 million years ago

  18. Fossil Record • Burgess Shale (580 million years old [Cambrian]) • many phyla present that are long extinct • some modern phyla represented • an “experiment of evolution”

  19. Fossil Record • oldest vertebrates >500 million years old • human agriculture ~10,000 years old • Therefore, human agriculture is about 0.00002% (two one-hundred thousandths of one per cent) as old as the oldest vertebrates • 0.00002% of a mile = 1/3 of a millimeter

  20. Fossil Record • ~99.9% of all metazoan species that have ever lived on Earth are extinct • of these estimated < 0.1% of animal species have been discovered as fossils

  21. Fossil Record • estimated that one in 10 million individual organisms end up as fossils • variable among taxa depending on presence of hard parts • What we know about past life on Earth (which is a lot) is based on a tiny sample.

  22. Common Descent • all forms of life ultimately descended from a common ancestor via a branching of lineages • single origin of life • overwhelming evidence (e.g., organismal form, cell structure, development, DNA)

  23. Common Descent: Phylogeny • structure of life is like a tree—phylogeny common ancestor of ratite birds

  24. Common Descent: Homology • “same organ in different organisms under every variety of form & function” (Owen) • e.g., limb skeleton of tetrapods from salamanders to humans share homologous elements

  25. Common Descent: Homology • homologous structures reflect common evolutionary ancestry • homologous structures used to generate phylogenetic hypotheses of relationships among organisms • “structures” can be macroscopic or at the molecular level (e.g., proteins, DNA)

  26. Common Descent: Homology • Whether or not two structures are homologous depends on the “level” being considered. • E.g., bird wing & bat wing grossly homologous • modified forelimb • but specific elements supporting the airfoil of each are not homologous • feathers in bird vs. skin in bat

  27. Common Descent: Homology

  28. Analogy • similar structures that serve similar function but do not indicate common ancestry • e.g., bird wing vs. butterfly wing

  29. Cladistics • cladogram—diagram of relationships among groups (like a phylogeny) generated using a specific methodology (i.e., cladistics)

  30. Phylogenetics & Cladistics • clade—group sharing derived character states • e.g., Squamata (lizards, snakes, amphisbaenians) Squamata (squamate reptiles)

  31. Phylogenetics & Cladistics • relationships are reconstructed based on shared derived characters—synapomorphies synapomorphy defining squamates w/in amniotes

  32. Phylogenetics & Cladistics • synapomorphies must be homologous characters across taxa in a clade synapomorphy defining squamates w/in amniotes

  33. Phylogenetics & Cladistics • shared ancestral characters do not define a clade • e.g., diapsid skull does not distinguish squamates as a group distinct from other diapsid amniotes ancestral for squamates w/in amniotes (b/c also shared w/ outgroups to squamates)

  34. Phylogenetics & Cladistics • polarity—directionality of ancestral/derived condition among groups (outgroup comparison) • e.g., presence of teeth is ancestral for amniotes & therefore lack of teeth is derived for birds • lack of teeth is a synapomorphy for birds teeth absent teeth absent teeth present

  35. Phylogenetics & Cladistics • in reality, branch tips represent species (lowest level non-reticulating lineage) • for illustration, branch tips can represent higher level taxa (e.g., genera, families, classes, orders)

  36. Phylogenetic Systematics • names of taxonomic groups based on identification of monophyletic groups (= clades) • monophyletic group—ancestor & all descendents • paraphyletic group—ancestor & some descendants • polyphyletic group—common ancestor not included teeth absent teeth absent teeth present

  37. Phylogenetic Systematics • EXAM PREPARATION: Come up w/ examples of each of these types of groupings. Be able to explain your answer. Feel free to come to office hours for help. teeth absent teeth absent teeth present

  38. common ancestor Multiplication of Species • well-accepted, but mechanistic details under constant study (as is the way of science) • evolution produces new species by the “splitting & transformation” of existing species • What is a species?

  39. What is a species? • Biological Species Concept (Mayr 1940) • an interbreeding natural population (or group of populations) that is reproductively isolated from other such groups • Evolutionary Species Concept (Simpson [1961] & Wiley [1981]) • a single lineage of ancestral-descendant populations that maintains its identity from other such lineages & that has its own evolutionary tendencies & historical fate • at least 30 other published species concepts

  40. Multiplication of Species • branch points (splits b/t lineages) on a phylogenetic tree represent speciation events • speciation = formation of new species • Note: Branch points also represent common ancestors that gave rise to descendant lineages.

  41. How does speciation occur? • evolution of reproductive barriers • can be physical, physiological, ecological, behavioral, etc. (frequently a combination) • generally accepted that the evolution of reproductive barriers b/t populations of animals requires the presence of geographic barriers (e.g., mountain range, isolated island) that physically separate populations

  42. How does speciation occur? • allopatric speciation • population separated into two separate groups by geographic barrier • followed by evolution of reproductive barriers • examples of geographic isolating mechanisms • formation of new mountain range separating population of low elevation species • formation of new island (e.g., land in ocean, lake on land) followed by rare immigration of individuals

  43. How does speciation occur? • examples of allopatric speciation • marine iguana & land iguana on Galapagos • reptiles on islands in Sea of Cortez • Hawaiian crow • squirrels on N & S rim of Grand Canyon • other speciation mechanisms exist, but allopatric speciation is most pervasive

  44. Adaptive Radiation • can arise from allopatric speciation • result evolution of many diverse species from a common ancestral stock • Darwin’s finches on Galapagos Islands • fruit flies on Hawaiian Islands • cichlid fish in African rift lakes • Anolis lizards on Caribbean Islands • elapid snakes in Australia • adaptive radiations typically associated w/ invasion of areas w/ unoccupied habitats or “niches” (e.g., islands)

  45. Adaptive Radiation

  46. Gradualism • major differences in traits among species evolve by accumulation of many small incremental changes over time • somewhat controversial phyletic gradualism

  47. Gradualism • theory of gradualism argues against sudden appearance of new species & rapid morphological changes • now accepted that new species can appear suddenly & that rapid morphological changes can evolve

  48. Alternative to Gradualism:Punctuated Equilibrium • sudden appearance of new species & rapid morphological changes followed by long periods of stasis • some patterns show gradualism & others indicate punctuated equilibrium • reality likely combination of both punctuated equilibrium

  49. Ontogeny & Phylogeny • ontogeny—development of organism throughout life • knowledge of ontogeny helps w/ understanding of homology, common descent, & phylogeny • alteration of development can generate novel phenotypes, which can result in big life history differences b/t organisms • difference b/t humans & chimps in expressed genes are mostly developmental genes

  50. Heterochrony • heterochrony—evolutionary change in timing of development • can be broad • e.g., humans exhibit extended early development & are born at an early stage • can be specific to certain structures • e.g., gills of axolotl retained throughout life