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Lecture 2: Evolution and Ecology EEES 3050 Excerpt from The Voyage of the Beagle (1845) 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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slide3
It is probable that the islands of the Cape de Verde group resemble, in all their physical conditions, far more closely the Galapagos Islands…
slide4
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.
natural diversity
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
    • 8,800–10,200 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
evolution disclaimer
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.”
what do scientists do
What do scientists do?
  • Explain
  • PREDICT!
  • Need a theory to make predictions.
other major scientific theories
Other major scientific theories.
  • Cell theory – 1839
  • Plate tectonic theory – not fully accepted until late 1960’s
  • 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.
what is evolution
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.
what evolution is by ernst mayr
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.
why is the theory of evolution important
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.
historical background early contributors
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
historical background biological issues
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.
historical background
Historical Background
  • Darwin’s 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.
historical background15
Historical Background
  • Darwin’s Five Theories
    • The non-constancy of species & common ancestors
      • Quickly accepted
    • Gradualism, speciation and natural selection.
      • Not completely accepted until 1940’s
slide16
Evidence for evolution
  • Fossil Record
  • Morphology
  • Vestigial organs
  • Biogeography
  • Molecular evidence
evidence for evolution fossil record18
Evidence for evolution: Fossil record
  • Jaw bone evolution from therapsid reptiles to mammals.
evidence for evolution fossil record19
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.
evidence for evolution
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
evidence for evolution21
Evidence for evolution
  • Vestigial Structures:
    • Structures that are not fully functional or functional at all.
evidence for evolution22
Evidence for evolution
  • Vestigial Structures
    • Blind cave dwelling animals still have eyes (that don’t work).
    • Why does an ostrich have wings?
evidence for evolution biogeography
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.
evidence for evolution26
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
mendelian genetics
Mendelian genetics
  • Gregor Mendel: 1822 – 1884
    • What did Mendel do?
    • Example: Green and yellow peas

Mendelian genetics was originally used to dispute one of Darwin’s theories.

maintaining genetic variation see appendix
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.
why does this matter
Why does this matter?
  • If population is not at equilibrium –
    • There are outside forces acting on the population.
outside forces that can change population genetics
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
loss of genetic variation
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)
current evolution
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?
examples
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
maintenance of variation
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.
evolutionary ecology
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 50:50), generalist vs. specialist feeding preferences, migration, number of offspring.
      • An evolutionary perspectives recognizes these phenomena change through time and in response to the environment.
evolutionary ecology39
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.
slide40
“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)
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