Vertebrate Zoology by yurtgc548

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									Vertebrate Zoology

     Chapter 1
    How do we learn from animals?
• Experimentation
    * Physiological Science
    1. How will a system respond to a disturbance?
    2. Create the disturbance
    3. Compare observations with expected results

• Comparison
    * Evolutionary Science
    * Comparative anatomy
    * Molecular biology
    * Cell biology
    * Ecology
Evolution Theories
      •   Perpetual Change
      •   Common Descent
      •   Multiplication of Species
      •   Gradualism
      •   Natural Selection
            Perpetual Change

Living organisms are not constant in
  form or function, nor are they
  perpetually cycling but always
  changing

Proposed in antiquity
           Common Descent

• All forms of life descended from a
  common ancestor through a branching
  of lineages (Phylogeny)

• Supported by DNA & cell structure
              Phylogeny
• The history of animal life depicted as a
  branching tree

• Earliest animals are placed at the trunk

• Each branch represents a new species
  which inherits many traits from the
  ancestor but also has a new (DERIVED)
  trait which appear for the 1st time
Phylogenetic Tree
          Multiplication of Species

• New species arise by the transformation
  of old ones
                Gradualism

• Differences in anatomical traits within
  different species accumulate over long
  periods of time
             Charles Darwin
              (1809-1882)
• Born in England
• Attended medical school,
  HATED IT, and dropped out
  to become a priest
• Boarded the H.M.S. Beagle
  for a 5 year UNPAID
  journey as a naturalist
Journey of the H.M.S. Beagle
Alfred Russel Wallace
     (1823-1913)
          Presented a paper with
          identical ideas as Darwin on
          July 1, 1858 at the Linnean
          Society meeting
          Was a botinist who came up
          with vitually the same
          concept of natural selection
          more or less independently
          through his studies on the
          Malay archipelago. Darwin
          panicked because he was not
          ready with his book yet!
Where did Darwin and
Wallace get the idea of
      evolution?
          Jean Baptiste Lamarck
               (1744-1829)
• Lamarck claimed that evolution
  was driven by "use vs. disuse"

• A used structure will become
  larger, stronger and more
  important.

• A disused structure will atrophy
  and become VESTIGIAL.
    Theory of “Use vs Disuse”
• The long necks of     • Similarly, the big,
  giraffes were due       “ripped” muscles
  to their stretching     developed by the
  for food, and           village blacksmith with
  giraffes passed         all his hammering and
  their stretched         slinging of heavy metal
  necks on to their       objects would be
  offspring.              expected to be passed
                          on to his offspring.
      Theory of “Acquired
       Characteristics”
• Lamarck claimed
  that traits
  acquired during an
  organism's lifetime
  could be inherited
  by that organism's
  offspring.
              Georges Cuvier
               (1769-1832)
• Created Paleontology
  (The study of fossils)

• He noted that deeper
  layers of sedimentary rock
  had diversity of organisms
  far different from present
  day life found in more
  recent layers
• Proposed the idea of
  extinction based on fossils
            James Hutton
             (1726-1797)
• A Scottish geologist who challenged
  Cuvier's view in 1795 with his idea of
  GRADUALISM
• Proposed that large changes in the
  earth's surface could be caused by slow,
  constant processes such as erosion.
                   Charles Lyell
                   (1797-1875)
• Earth processes had been going on
  constantly, and could explain the
  appearance of the earth.

• This theory, uniformitarianism, was
  a strong basis for Darwin's later
  theory of natural selection.
         Thomas Malthus
          (1766-1834)
• Suggested that much of humanity's
  suffering (disease, famine, homelessness
  and war) was the inevitable result of
  overpopulation: humans reproduced more
  quickly than their food supply could
  support them.
• Malthus showed that populations, if
  allowed to grow unchecked, increase at a
  geometric rate.
        Darwin made some profound
    observations, from which he inferred
         some brilliant conclusions...

• Observation #1. All species have huge potential fertility

• Observation #2. Except for seasonal fluctuations,
  populations tend to maintain a stable size.

• Observation #3. Environmental resources are limited.
            Inference #1
• The production of more individuals than the
  environment can support leads to a "struggle
  for existence," with only a fraction of
  offspring surviving in each generation.
            Observations
• Observation #4: No two individuals in a
  population are exactly alike

• Observation #5: Much of the observed
  variation in a population is heritable
             Inference #2
• Survival in this "struggle for existence is not
  random, but depends, in part, on the
  hereditary makeup of the survivors.

• Those individuals who inherit characteristics
  that allow them to best exploit their
  environment are likely to leave more offspring
  than individuals who are less well suited to their
  environment.
                 Inference #3
• Unequal reproduction between suited and unsuited
  organisms will eventually cause a gradual change in a
  population, with characteristics favorable to that
  particular environment accumulating over the generations.
SO WHAT IS THIS THEORY
OF NATURAL SELECTION?



  It can be broken down into four
       basic tenets, or ideas
  Theory of Natural Selection

• 1. Organisms are capable of producing huge
  numbers of offspring.

• 2. Those offspring are variable in appearance
  and function, and some of those variations are
  heritable.
 Theory of Natural Selection
• 3. Environmental resources are limited, and
  those varied offspring must compete for their
  share.
• 4. Survival and reproduction of the varied
  offspring is not random. Those individuals
  whose inherited characteristics make them
  better able to compete for resources will live
  longer and leave more offspring than those not
  as able to compete for those limited
  resources.
 What is speciation and who
         studies it?
• Speciation is the creation of a new
  species
• Scientists who study the processes
  and mechanisms that lead to such
  speciation events are
  EVOLUTIONARY BIOLOGISTS.
      Allopatric Speciation

• A population becomes physically separated
  from the rest of the species by a
  geographical barrier that prevents
  interbreeding.

• Because gene flow is disrupted by this
  physical barrier, new species will form.
    Sympatric Speciation
• Two populations are geographically
  close to each other, but they are
  reproductively isolated from each
  other by different habitats, mating
  seasons, etc.
       Reproductive Barriers
A reproductive barrier is any factor that prevents
  two species from producing fertile hybrids, thus
  contributing to reproductive isolation.

•   Habitat Isolation
•   Temporal Isolation
•   Behavioral Isolation
•   Mechanical Isolation
•   Gametic Isolation
              Species
• A SPECIES is a group of similar
  organisms that can mate to produce
  fertile, viable offspring.

• Different species are, by definition,
  REPRODUCTIVELY ISOLATED from
  one another.
      Adaptive Radiation
• Adaptive Radiation - Evolutionary
  process in which the original species
  gives rise to many new species, each
  of which is adapted to a new habitat
  and a new way of life.
      E.g. Darwin's Finches
    Evidence for Evolution

              HOMOLOGY
• In biology, a HOMOLOGY is a
  characteristic shared by two species
  (or other taxa) that is similar
  because of common ancestry.
         Types of homology
• morphological homology – species placed in the
  same taxonomic category show anatomical
  similarities.
• ontogenetic homology - species placed in the
  same taxonomic category show developmental
  (embryological) similarities.
• molecular homology - species placed in the
  same taxonomic category show similarities in
  DNA and RNA.
         MORPHOLOGICAL
           HOMOLOGY
• Structures derived from a common ancestral
  structure are called:


 HOMOLOGOUS STRUCTURES
    Ontogenetic Homology
The human embryo has gills, a tail,
 webbing between the toes & fingers, &
 spends its entire time floating and
 developing in amniotic fluid has similar
 salt concentration as ocean water
      MORPHOLOGICAL
        HOMOLOGY
• A structure that serves the same
  function in two taxa, but is NOT
  derived from a common ancestral
  structure is said to be an


ANALOGOUS STRUCTURE
    Examples of Analogous
        structures:
• wings of bat, bird, and butterfly

• walking limbs of insects and vertebrates

• cranium of vertebrates and exoskeleton
  head of insects
Molecular Homology
      An ongoing process
• Evolution can be considered a process
  of "remodeling" a population over the
  course of many generations, with the
  driving force being the natural
  selection factors that favor one form
  over another in specific environments.
     Vestigial Structures

• Have marginal, if any use to the
  organims in which they occur.
• EXAMPLES:
• pelvic elements in pythonid snakes and
  cetaceans (whales)
• appendix in humans
• coccyx in great apes
Whale Pelvis?
         Types of Evolution
• Divergent Evolution - Method of evolution
  accounting for the presence of homologous
  structures. Multiple species of organisms
  descended from the same common ancestor at
  some point in the past.

• Convergent Evolution - Method of evolution
  accounting for the presence of analogous
  structures. Organisms of different species often
  live in similar environments, thus explaining the
  presence of features with similar functions.
         Rate of Evolution
• Gradual evolution occurs where the
  increment of change is small compared to
  that of time.
• Punctuated evolution occurs where the
  increment of change is very large
  compared to that of time in discrete
  intervals, while most of the time there is
  virtually no change at all.
Natural Selection in Action
   Industrial Melanism
Natural Selection in Action
       Camouflage
Natural Selection in Action
         Mimicry

   Coral vs. King Snakes:
   Red on yellow, kill a fellow,
   red on black won’t hurt Jack
Natural Selection in Action
   Warning Coloration
Natural Selection in Action
  Disruptive Coloration
Natural Selection in Action
    Counter Shading
Natural Selection in Action:
        Eye Spots
          Causes of Evolution
1.   Mutations - random changes in genetic material at the
     level of the DNA nucleotides or entire chromosomes

2.   Natural Selection - most important cause of evolution;
     measured in terms of an organism's fitness, which is its
     ability to produce surviving offspring

     a. Stabilizing Selection - average phenotypes have a
     selective advantage over the extreme phenotypes

     b. Directional Selection - phenotype at one extreme has
     a selective advantage over those at the other extreme

     c. Disruptive Selection - both extreme phenotypes are
     favored over the intermediate phenotypes
Natural selection favors the average individuals
within a population
Natural selection favors on one of the extreme
variations within a species
Individuals with both extreme phenotypes are selected for
          Causes of Evolution
3. Mating Preferences - Organisms usually do not choose their
   mates at random, thus the selection process can cause
   evolution

4. Gene Flow - Transfer of genes between different
  populations of organisms. This situation leads to increased
  similarity between the two populations

5. Genetic Drift (Founder Effect & Bottleneck) - Situation
  that results in changes to a population's gene pool caused by
  random events, not natural selection. This situation can have
  drastic effects on small populations of individuals. Common
  on islands.
Gene Flow
                          Genetic Drift

The change in gene
frequency in a
population resulting in
different phenotypes
Founder Effect
Bottleneck Effect
       The study of phylogeny
• Understanding a phylogeny is a lot like reading a family
  tree.
• The root of the tree represents the ancestral lineage,
  and the tips of the branches represent the descendents
  of that ancestor.
• As you move from the root to the tips, you are moving
  forward in time.
         Phylogenic Speciation
• When a lineage splits (speciation), it is represented
  as branching on a phylogeny.
• When a speciation event occurs, a single ancestral
  lineage gives rise to two or more daughter lineages.
             Shared Ancestry
• Phylogenies trace patterns of shared ancestry
  between lineages.

•    Each lineage has a part of its history that is
    unique to it alone and parts that are shared with
    other lineages.
      Common Ancestors
• Each lineage has ancestors that are
  unique to that lineage and ancestors
  that are shared with other lineages —
  called common ancestors.
     Clades – Cladistics (The
         study of clades)
• A clade is a grouping that includes a common
  ancestor and all the descendents (living and extinct)
  of that ancestor.
            Nested Clades
• Clades are nested within one another — they form
  a nested hierarchy.

• A clade may include many thousands of species or
  just a few.
               Reading Phylogeny

Evolution produces a pattern of relationships A B C D
among lineages that is tree-like, not ladder-like.
                Reading Phylogeny

Just because we tend to read phylogenies from left to
right, there is no correlation with level of "advancement."
                Reading Phylogeny

For any speciation event on a phylogeny, the choice of
which lineage goes to the right and which goes to the left
is arbitrary. The following phylogenies are equivalent:
Misconceptions about humans



It is important to remember that:
1. Humans did not evolve from chimpanzees. Humans
   and chimpanzees are evolutionary cousins and
   share a recent common ancestor that was neither
   chimpanzee nor human.


2. Humans are not "higher" or "more evolved" than
   other living lineages. Since our lineages split,
   humans and chimpanzees have each evolved traits
   unique to their own lineages.
                 Character Types
• A character is a recognizable feature of an organism. Characters
  may be morphological, behavioral, physiological, or molecular.

• A shared character is one that two lineages have in common

• A derived character is one that evolved in the lineage leading up to
  a clade and that sets members of that clade apart from other
  individuals.

• Shared derived characters can be used to group organisms into
  clades. For example, amphibians, turtles, lizards, snakes, crocodiles,
  birds and mammals all have, or historically had, four limbs.
Review
So What Does This Mean?

								
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