Organic Evolution

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Organic Evolution Natural Selection
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Organic Evolution

• changes in life through time
• development of complex life forms
• development of a variety of life forms

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Natural Selection

• mechanism responsible for evolution
• through mutation and selection
• survival of the
• fittest (for a niche)
• luckiest
• combination

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Scientific Explanations

• must be natural
• must be supported by available data
• must be testable falsifiable
• subject to revision or refinement or negation
• should be predictive
• OE and NS meet all of these requirements

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Theory Hypothesis

• Hypothesis
• a working explanation or educated guess
• competing hypotheses are often investigated
  simultaneously
• Theory
• the best explanation supported by a preponderance
  of the evidence
• the best a scientist can hope for

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Terminology

• species
• reproductively isolated group of living organisms
• population
• group of organisms consisting of all the members
  of a species living in an area

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Organic evolution observations

• sedimentary rocks
• deposited in layers
• oldest layers are on the bottom
• layers may be correlated with layers in other
  areas
• conclusions
• relative time scale
• the Earth is very old
• confirmed with absolute dating

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Organic evolution observations

• fossil record
• oldest rocks have only simple fossils
• younger rocks have more organisms similar to
  those living today (at levels from species to
  kingdom)
• fossils record includes appearances and
  extinctions of many species

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Organic evolution observations

• geographic distribution of organisms
• many organisms are similar but unique
• they are confined to specific areas (islands,
  continents, water bodies)
• includes modern and fossil organisms
• distribution has changed through time

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Organic evolution observations

• anatomy
• cell structure is similar in all living organisms
• embryology - embryos of mammals, birds, and
  reptiles are very similar
• homologus organs - similar organs, different
  functions
• vestigal organs - no purpose in one, purpose in
  another

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Organic evolution observations

• genetics
• structure of DNA and RNA is the same in all
  living organisms
• similarity in genetic code varies between
  organisms (some organisms are more similar than
  others)
• mitochondrial and plasmid DNA
• separate from nuclear DNA
• similar to some bacteria

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Organic evolution observations

• cladistic analyses
• statistical examination using
• anatomy
• DNA
• behavior
• indicates strength of affinity between species

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Organic evolution observations

• combining data
• cladistic analyses of fossils and living species
• time data (relative absolute)
• spatial relationships
• (where fossils and living populations are
  found)
• reveals phylogeny
• (tree of life through time)

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Organic evolution conclusions

• the characteristics of populations of living
  organisms have changed through time
• life has become more complex
• life has become more diverse
• all life is related
• this is accepted as a factual observation

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Evolutionary Trends

• divergence speciation
• extinction
• convergence
• phyletic gradualism
• punctuated equilibrium

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Organic evolutionMissing links!!!

• the link between two fossil species OR between
  a fossil species and a living species
• PRESERVATION AS A FOSSIL IS RARE!
• many links found (its just a matter of time
  and effort)
• however each gap filled creates two new gaps

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Question

• What is the mechanism that resulted in the
  evolution of life?

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Natural selection observations

• populations of organisms display a variety of
  characteristics
• characteristics may be useful, not useful, or
  detrimental
• the variety is reflected in an organisms genes

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Natural selection observations

• new genes provided by
• mutation
• duplication
• exchange
• passed to offspring during reproduction

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Natural selection observations

• Symbiosis
• Living organisms in close proximity, at least one
  of the symbionts cannot live without the other
• Symbiotic relationships can result in new
  characteristics

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Natural selection observations

• artificial selection
• domesticated plants and animals can be bred to
  favor certain characteristics
• ONLY individuals with desired characteristics are
  allowed to breed
• descendant populations of plants and animals are
  dominated by characteristics that are desired by
  breeders
• and thus favored their survival

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Natural selection observations

• The natural environment acts as a selective
  breeder
• contains opportunities and stresses for living
  organisms
• selection is enhanced by
• stress on an existing niche
• a new niche

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Natural selection observations

• Populations of a species may become isolated by
  geography or behavior
• Isolation
• provides new opportunities and stresses
• isolates the population from the larger gene pool

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Conclusion

• The variety of conditions in the natural
  environment results in natural selection of
  populations which, in turn, is responsible for
  biological evolution.

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Natural selection details

• organisms with favorable characteristics for
  their niche are more likely to thrive and
  reproduce while organisms with unfavorable
  characteristics are less likely to thrive and
  reproduce
• over time, favorable characteristics can
  accumulate in a population until the members of
  the population can no longer reproduce with the
  population from which they became isolated

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Natural selection details

• genetic changes
• favorable more likely to be passed on to
  offspring
• neutral likely to be passed on to offspring
• unfavorable less likely to be passed on to
  offspring
• natural selection is not random

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Evolutionary trends

• divergence, speciation, extinction
• convergence
• homology vestigal organs
• coevolution symbiogenesis
• phyletic gradualism punctuated equilibrium

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Divergence Speciation

• a population has a gene pool
• members of the population interbreed
• the population may become isolated from others of
  a species
• development of niches resource partitioning
• migration
• development of physical barriers
• populations may be selected
• by stress
• by opportunity
• isolation may result in genetic divergence
  speciation

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Extinction

• stress on limiting factors destroy a population
• divergent evolution into subsequent species
  (pseudo-extinction)

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Convergence

• Characteristics of a habitat favor certain styles
  of adaptation
• e.g. streamlined shape, tooth shape
• Natural selection results in organisms in similar
  niches having similar forms
• Similar forms resulting from convergence usually
  do not have similar underlying structures

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Homology Vestigial Organs

• a slightly modified organ or organ system my
  provide advantage in a niche
• when the modification results in selection
  generation after generation, the modification may
  become enhanced
• when compared with closely related species, the
  organ or organ system will have the same parts
  used for different functions (homology) and some
  parts may no longer be in use (vestigial)

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Coevolution Symbiogenisis

• A niche may be associated with another organism
• The characteristics that favor interdependence
  may be subject to continued selection
  (coevolution)
• Selection that favors an organic niche may
  result in dependence or interdependence
  (symbiosis)
• Symbiotic relationships may become permanent due
  to genetic exchange and/or incorporation
  (symbiogenesis)

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Phylogeny

• relationships between organisms can be determined
  using
• genetics
• anatomy physiology
• fossils

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Phyletic Gradualism Punctuated Equilibrium

• gradualism
• slow, steady change
• equilibrium punctuation
• long periods with little change
• short bursts of rapid change

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How did it start?

• Chemical evolution
• needs energy, but no oxygen
• simple compounds form(CO2, NH3)
• organic compounds form (amino acids, nucleic
  acids)
• organic compounds assemble (microspherules,
  bubbles, clay particles, ice crystals)
• First life simple, wall-less, fermenting
  bacteria
• Where?
• deep ocean vents, tidal pools, ice sheet, clay
  sediment

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Randomness

• mutations are random
• evolution is not random
• natural selection is not random
• favorable mutations survive through reproduction

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End point

• Evolution has no end