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Vertebrate Zoology Dr. A. Kristopher Lappin is attending the meeting 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 Vertebrate Zoology

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Vertebrate Zoology


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vertebrate zoology
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

vertebrate zoology2
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
goals of course
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
definitions of biological disciplines
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
some biological levels of organization
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
some biological levels of organization6
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.
what is a theory
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.
theory of evolution
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)
influences on darwin
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
influences on darwin10
Influences on Darwin
  • voyage of the H.M.S. Beagle
  • Darwin 23 years old
  • 5-year voyage around the world
influences on darwin11
Influences on Darwin
  • observed & collected fauna & flora
  • found fossils
  • found seashells in mountains at 4,000 meters
  • experienced major earthquake in S. America
influences on darwin12
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
influences on darwin13
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)
perpetual change geological time
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
evidence of perpetual change
Evidence of Perpetual Change

Banded Iron Formation, Australia

  • rocks up to 3 billion years old
evidence of perpetual change16
Evidence of Perpetual Change

Big Island, Hawaii

  • oldest part of island 400,000 years old (7,500 times younger than the old rocks)
fossil record
Fossil Record
  • oldest microscopic fossils—3.5 billion years
  • oldest macroscopic fossils—650 million years
  • most animal phyla present 540 million years ago
fossil record18
Fossil Record
  • Burgess Shale (580 million years old [Cambrian])
      • many phyla present that are long extinct
      • some modern phyla represented
      • an “experiment of evolution”
fossil record19
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
fossil record20
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
fossil record21
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.
common descent
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)
common descent phylogeny
Common Descent: Phylogeny
  • structure of life is like a tree—phylogeny

common ancestor of ratite birds

common descent homology
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
common descent homology25
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)
common descent homology26
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
analogy
Analogy
  • similar structures that serve similar function but do not indicate common ancestry
    • e.g., bird wing vs. butterfly wing
cladistics
Cladistics
  • cladogram—diagram of relationships among groups (like a phylogeny) generated using a specific methodology (i.e., cladistics)
phylogenetics cladistics
Phylogenetics & Cladistics
  • clade—group sharing derived character states
    • e.g., Squamata (lizards, snakes, amphisbaenians)

Squamata

(squamate reptiles)

phylogenetics cladistics31
Phylogenetics & Cladistics
  • relationships are reconstructed based on shared derived characters—synapomorphies

synapomorphy defining squamates

w/in amniotes

phylogenetics cladistics32
Phylogenetics & Cladistics
  • synapomorphies must be homologous characters across taxa in a clade

synapomorphy defining squamates

w/in amniotes

phylogenetics cladistics33
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)

phylogenetics cladistics34
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

phylogenetics cladistics35
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)
phylogenetic systematics
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

phylogenetic systematics37
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

multiplication of species

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?
what is a species
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
multiplication of species40
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.
how does speciation occur
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
how does speciation occur42
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
how does speciation occur43
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
adaptive radiation
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)
gradualism
Gradualism
  • major differences in traits among species evolve by accumulation of many small incremental changes over time
  • somewhat controversial

phyletic gradualism

gradualism47
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
alternative to gradualism punctuated equilibrium
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

ontogeny phylogeny
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
heterochrony
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
natural selection
Natural Selection
  • proposed by Darwin (and Wallace)
  • supported by abundant evidence
  • describes how populations accrue ‘favorable’ characteristics over evolutionary time
  • evidence from artificial selection
    • e.g., dog breeds
  • supported by series of observations & inferences from those observations
natural selection52
Natural Selection
  • organisms have great reproductive potential & many more are produced than can survive (Malthus)
  • populations fluctuate in size but do not show the continuous exponential increase that they would w/out some limitation
  • resources limited, so not all offspring can survive (Malthus)
natural selection53
Natural Selection
  • Inference: struggle for existence among individuals in a population that increases w/ greater numbers of individuals (Malthus)
  • all organisms show variation (random)
  • variation is heritable
    • e.g., you look & act like your parents (or at least you will eventually)
natural selection54
Natural Selection
  • Inference: differential survival & reproduction among individuals
  • Inference: differential survival & reproduction generate new adaptations & species
    • consider how natural selection could generate changes over geological time
    • artificial selection (breeding) generates radical changes in human lifetimes
slide58

Evolutionary Concepts

  • convergence
  • reduction, loss, reversal
  • specialization
slide59

Convergence

  • independent evolution of a similar characteristic in two or more taxa
  • morphology, physiology, ecology, behavior, etc.—often a combination
  • presence of similarity not due to common ancestry
slide60

Convergence

  • Lizards & mice both have four limbs. Is this convergence?
slide61

Convergence

  • Lizards & mice both have four limbs.
  • Is this convergence?
  • No
    • The presence of four limbs in both lizards & mice is explained by common ancestry.
    • How do the terms homology, analogy, & synapomorphy apply to this situation?
slide62

Convergence

  • Birds & bats both have wings. Is this convergence?
slide63

Convergence

  • Birds & bats both have wings.
  • Is this convergence?
  • Yes
    • evolved wings independently
    • common ancestor did not have wings
    • wings of both taxa are modified forelimbs
    • How do the terms homology, analogy, derived, & synapomorphy apply to this situation?
slide64

Birds: elongation & fusion of 3rd & 4th metacarpals plus 3rd digit provides support for airfoil of feathers (primarily) .

Bats: elongation of 2nd through 5th metacarpals & digits provides support for airfoil of skin.

slide65

Reduction & Loss

  • usually refers to morphology
  • reduction in size or prominence of a feature or element
  • loss of a morphological element
slide66

Reduction & Loss

  • Example: In the major evolutionary transitions from one taxon to another (e.g., fish to amphibian, amphibian to reptile, reptile to mammal), reduction & loss of skull elements is typical.
  • Humans have relatively simple skull & jaw structure (i.e., few elements). This is an example of simplification in a highly derived taxon.
slide68

Comparison:

Fish vs. Amphibian

dorsal view

slide69

Comparison:

Ancestral Reptile vs. Snake

dorsal view

slide70

Comparison:

Ancestral Reptile vs. Bird

dorsal view

slide71

Comparison:

Ancestral “Reptile” vs. Mammal

dorsal view

slide72

Reversal

  • evolutionary return to a condition seen in an ancestor
  • “secondarily derived”
  • determined by analysis w/in a phylogenetic framework
slide73

Reversal

  • Example: Some Great Apes (that includes you) are secondarily terrestrial.
  • Ancestral primates evolved from terrestrial forms, became arboreal, then secondarily evolved terrestriality (maybe due to disappearance of forests & expansion of savannas).
slide74

Specialization

  • morphological, physiological, and/or behavioral modification for a specialized biological role
  • considered an adaptation if current biological role of characteristic is same as its original role when it evolved
slide75

Specialization

  • Example: egg-eating snakes (Dasypeltis)
    • specialized behavior—egg-eating
    • specialized ecology—gorge/fast strategy matches seasonal availability of prey
    • specialized morphology
      • extra scale rows on throat
      • vertebral processes protrude into esophagus
      • few teeth (loss / reduction)
      • extra elongation of quadrate bones
      • others
what evolution is is not
What Evolution Is & Is Not
  • Evolution is not like a ladder. Evolution is like a tree.
  • The parts of an organism (i.e., its characteristics) can be ancestral or derived, depending on what other organisms it is being compared to.
  • An organism is the sum of its parts. Therefore, an organism is a composite of ancestral & derived characteristics.
    • Avoid using the terms primitive & advanced in reference to organisms or taxonomic groups.
slide78

Evolution is the unifying theme of biology. Everything biological is its product.Everything biological makes sense only in the light of evolutionary theory.

slide79

Darwin Quotes

“I have called this principle, by which each slight variation, if useful, is preserved, by the term of Natural Selection.”

“On the ordinary view of each species having been independently created, we gain no scientific explanation.”

“The universe we observe has precisely the properties we should expect if there is, at bottom, no design, no purpose, no evil, no good, nothing but blind, pitiless indifference.”

“What a book a devil's chaplain might write on the clumsy, wasteful, blundering, low, and horribly cruel work of nature!”

--Charles Darwin