Vertebrate Zoology

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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

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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

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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

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Definitions of Biological Disciplines

• evolutionchange through time
• biodiversityvariety of living forms their
  habits
• anatomy physiologystructure function
• behaviorhow animals do things
• ecologyinteractions of animals w/ each other
  their physical environments

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Some Biological Levels of Organization

• how molecules w/in cells interactmolecular
  biology
• how cells functioncell biology
• how tissues/organs of an individual organism
  function interactphysiology

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Some Biological Levels of Organization

• how individuals w/in a species interactpopulation
  biology
• intraspecific level
• how different kinds of organisms
  interactcommunity ecology
• interspecific level
• Relate levels of organization when comparing
  organisms to better understand evolutionary
  trends.

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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.

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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)

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Influences on Darwin

• Lamark
• first scientific explanation of evolution
• inheritance of acquired characteristics
• made case that fossils are remains of extinct
  animals
• Lyell
• uniformitarianismsame physical laws geological
  processes operate now as during Earths history

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Influences on Darwin

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

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Influences on Darwin

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

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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

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Influences on Darwin

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

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Perpetual Change Geological Time

• Perpetual geological biological change is the
  rule.
• Consider the vastness of geological time.
• radiometric dating
• age of Earth4.6 billion years

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Evidence of Perpetual Change

• Banded Iron Formation, Australia
• rocks up to 3 billion years old

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Evidence of Perpetual Change

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

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Fossil Record

• oldest microscopic fossils3.5 billion years
• oldest macroscopic fossils650 million years
• most animal phyla present 540 million years ago

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Fossil Record

• Burgess Shale (580 million years old Cambrian)
• many phyla present that are long extinct
• some modern phyla represented
• an experiment of evolution

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Fossil Record

• oldest vertebrates gt500 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

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Fossil Record

• 99.9 of all metazoan species that have ever
  lived on Earth are extinct
• of these estimated lt 0.1 of animal species have
  been discovered as fossils

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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.

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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)

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Common Descent Phylogeny

• structure of life is like a treephylogeny

common ancestor of ratite birds
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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

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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)

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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

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Common Descent Homology
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Analogy

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

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Cladistics

• cladogramdiagram of relationships among groups
  (like a phylogeny) generated using a specific
  methodology (i.e., cladistics)

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Phylogenetics Cladistics

• cladegroup sharing derived character states
• e.g., Squamata (lizards, snakes, amphisbaenians)

Squamata (squamate reptiles)
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Phylogenetics Cladistics

• relationships are reconstructed based on shared
  derived characterssynapomorphies

synapomorphy defining squamates w/in amniotes
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Phylogenetics Cladistics

• synapomorphies must be homologous characters
  across taxa in a clade

synapomorphy defining squamates w/in amniotes
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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)
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Phylogenetics Cladistics

• polaritydirectionality 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
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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)

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Phylogenetic Systematics

• names of taxonomic groups based on identification
  of monophyletic groups ( clades)
• monophyletic groupancestor all descendents
• paraphyletic groupancestor some descendants
• polyphyletic groupcommon ancestor not included

teeth absent
teeth absent
teeth present
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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
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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?

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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

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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.

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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

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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

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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

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Adaptive Radiation

• can arise from allopatric speciation
• result evolution of many diverse species from a
  common ancestral stock
• Darwins 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)

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Adaptive Radiation
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Gradualism

• major differences in traits among species evolve
  by accumulation of many small incremental changes
  over time
• somewhat controversial

phyletic gradualism
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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

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Alternative to GradualismPunctuated 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
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Ontogeny Phylogeny

• ontogenydevelopment 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

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Heterochrony

• heterochronyevolutionary 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

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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

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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)

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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)

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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

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Evolutionary Concepts

• convergence
• reduction, loss, reversal
• specialization

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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

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Convergence

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

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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?

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Convergence

• Birds bats both have wings. Is this
  convergence?

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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?

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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.
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Reduction Loss

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

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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.

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Complexity of Fish Skull
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Comparison Fish vs. Amphibian
dorsal view
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Comparison Ancestral Reptile vs. Snake
dorsal view
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Comparison Ancestral Reptile vs. Bird
dorsal view
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Comparison Ancestral Reptile vs. Mammal
dorsal view
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Reversal

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

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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).

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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

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Specialization

• Example egg-eating snakes (Dasypeltis)
• specialized behavioregg-eating
• specialized ecologygorge/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

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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.

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