Lecture 2: Evolution and Ecology

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Lecture 2 Evolution and Ecology

• EEES 3050

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Excerpt from The Voyage of the Beagle (1845)
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• It is probable that the islands of the Cape de
  Verde group resemble, in all their physical
  conditions, far more closely the Galapagos
  Islands

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• yet the aboriginal inhabitants of the two groups
  are totally unlike those of the Cape de Verde
  Islands bearing the impress of Africa, as the
  inhabitants of the Galapagos Archipelago are
  stamped with that of America.

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Natural Diversity

• By the Numbers
• Estimated 2 - 100 million species, with a best
  estimate of somewhere near 10 million
  
• 1.4 million described species
• 1 million described insects/ 350,000 described
  beetles
  
• 8,80010,200 living bird species
• 5,500 species of mammals
• Great diversity exists, with each species
  exhibiting a considerable degree of suitability
  for its natural lifestyle
  
• How?
• Seems unlikely

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Evolution Disclaimer

• Whether you choose to believe that evolution is
  the means by which existing species diversity
  developed or not, you are responsible for
  learning and applying the principles in this
  course.
• In short This course will be taught from the
  evolutionary paradigm.
  

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What do scientists do?

• Explain
• PREDICT!
• Need a theory to make predictions.

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Other major scientific theories.

• Cell theory 1839
• Plate tectonic theory not fully accepted until
  late 1960s
  
• General relativity (i.e. gravitational theory)
  proposed by Einstein in 1915/16.
  
• Gravitational waves are a requirement of the
  theory of general relativity, but have never been
  directly detected
  
• Gravitational waves have been generally been
  accepted to exist since 1980s.
  
• Chemistry Valence bond theory and molecular
  orbital theory
  
• Competing theories in the 1930s. Now somewhat
  combined also the advent of quantum chemistry.

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What is evolution?

• Broad The gradual process by which the living
  world has been developing following the origin of
  life.
  
• Narrow Change in the genetic frequencies of a
  population.

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What Evolution Is? By Ernst Mayr

• Evolution is the most important concept in
  biology. There is not a single Why? question in
  biology that can answered adequately without a
  consideration of evolution.
• Again need theory for explanation and prediction.

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Why is the theory of evolution important?

• Implications for people
• Antibiotic resistance, pesticide resistance,
  control of disease, human epidemiology,
  development of new crops, medical treatments,
  conservation biology, etc. (not to mention the
  ecological implications)
• Evolution provides the mechanism to address these
  issues.
  

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Historical Background Early contributors

• Lamark (1809) Inheritance of Acquired
• Characteristics (learning meme vs. gene)
• Darwin Theory of Evolution (Origin of Species
  1859)
  
• 5 theories really.
• Malthus potential usually exceeds realized
  reproduction for populations (including humans)
  
• Wallace independent conceptualization of Natural
  Selection
  
• Mendel Genetics currency of evolution

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Historical Background Biological issues

• In 17th Century and prior
• Natural history
• Segregated into zoology and botany
• Medicine
• Segregated into anatomy, physiology, surgery, and
  clinical medicine.
  
• Evolution and genetics unified all these
  disciplines.
  

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Historical Background

• Darwins Five Theories
• 1 The non-constancy of species
• The idea of a changing world can be considered
  the fact of evolution.
  
• 2 The descent of all organisms from common
  ancestors
  
• 3 Gradualism (no saltations, no
  discontinuities)
  
• 4 Speciation by populations
• 5 Natural selection
• This is the theory of the process of evolution.
  

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Historical Background

• Darwins Five Theories
• The non-constancy of species common ancestors
• Quickly accepted
• Gradualism, speciation and natural selection.
• Not completely accepted until 1940s

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Evidence for evolution

• Fossil Record
• Morphology
• Vestigial organs
• Biogeography
• Molecular evidence

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Evidence for evolution Fossil record
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Evidence for evolution Fossil record

• Jaw bone evolution from therapsid reptiles to
  mammals.

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Evidence for evolution Fossil record

• Evolution through time
• Variation through geologic periods.
• Fossils in most recent strata are often similar
  if not indistinguishable from living species.
  
• The older the strata is, the more different the
  fossils.

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Evidence for evolution

• Morphology
• This was how species were described as related
  as far back as 18th century.
  
• Linnaean hierarchy
• From Kingdom to sub-species

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Evidence for evolution

• Vestigial Structures
• Structures that are not fully functional or
  functional at all.

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Evidence for evolution

• Vestigial Structures
• Blind cave dwelling animals still have eyes (that
  dont work).
  
• Why does an ostrich have wings?

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Evidence for evolution Biogeography

• Biogeography
• the geographic distribution of organisms
• those organisms of the Cape de Verde Islands
  bearing the impress of Africa, as the inhabitants
  of the Galapagos Archipelago are stamped with
  that of America.

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Evidence for evolution Biogeography

• Evolution through space

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Gondwana
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Evidence for evolution

• Molecular evidence
• the more closely related two organisms are, the
  more similar are their genetic structure.
  
• Often times, morphological traits can be
  ambiguous.
  
• One of the most important sources of information
  on phylogenetic relationships

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Mendelian genetics

• Gregor Mendel 1822 1884
• What did Mendel do?
• Example Green and yellow peas

Mendelian genetics was originally used to dispute
one of Darwins theories.
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Maintaining Genetic Variation See appendix.

• Without Selection no loss or gain (random)
• B. Hardy-Weinberg Theorem constant allelic
  frequencies are maintained if ...
  
• populations are large,
• individuals contribute equally to genetic
  composition of next generation, and
  
• matings are random
• Remember Narrow definition of evolution change
  in the genetic frequency of a population.

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Why does this matter?

• If population is not at equilibrium
• There are outside forces acting on the
  population.
  

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Outside forces that can change population
genetics.

• Mutations
• origin of variations, and mutation increases
  under stress
  
• Age, chemicals, UV-radiation
• Migration
• Population size
• Non-Random Mating
• Nonrandom Mating ? gene frequencies
• Environmental Variance favor some phenotypes
• Effects of Selection stable polymorphisms
• Natural Selection

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Loss of Genetic Variation

• Inbreeding rapid loss of genes
• Fixes traits quickly
• Genetic Drift random losses of genes
• Neighborhoods local breeding tendency
• Races of plants and animals
• Bottlenecks low population reduced pool,
  duration of the low population is critical (drift)

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• Survivors of a near-extinction resulted in close
  inbreeding 10,000 years ago.

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Current Evolution

• According to narrow definition
• Evolution is little more than a process that
  changes gene frequencies in a non-random manner
  
  
• environmental influences direct this change
• What are a few examples of recent evolution of
  species that can be correlated to an
  environmental stress?

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Examples

• The evolution of pesticide resistence in pest
  species
  
• The evolution of antibiotic resistence in human
  pathogens
  
• note the recent discovery of plague and
  tuberculosis exhibiting broad-spectrum antibiotic
  resistence

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Insect species resistant to pesticides
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Strep resistance to penicillin
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Maintenance of variation

• So how is variation maintained in the face of
  environmental pressures and natural selection?
  
• Ever see a constant environment?
• Microenvironmental differences exist over small
  spatial scales.
  
• Temporal heterogeneity is a common characteristic
  of physical environments.

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Evolutionary Ecology

• Fusion of ecology and evolutionary theory.
• Sometimes two terms used as different time
  scales.
  
• An observed relationship may be explained by
• functional, proximate or ecological means.
• Or ultimate, evolutionary terms.
• Historically, ecologists assumed many phenomena
  are immutable
  
• Sex ratios (always 5050), generalist vs.
  specialist feeding preferences, migration, number
  of offspring.
  
• An evolutionary perspectives recognizes these
  phenomena change through time and in response to
  the environment.

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Evolutionary Ecology

• Evolution is a primary factor in determining the
  distribution and abundance of organisms.
  
• A relatively new field (last 25 year).
• Thus not adequately addressed in most text books.
  
  

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• There is grandeur in this view of life, with its
  several powers, having been originally breathed
  by the Creator into a few forms or into one and
  that whilst this planet has gone cycling on
  according to the fixed laws of gravity, from so
  simple a beginning endless forms most beautiful
  and most wonderful have been, and are being
  evolved.
• Charles Darwin The Origin of Species (Last
  sentence)