Charles Darwin

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Charles Darwin

• Lived from 1809-1882
• Considered the founder of modern evolutionary
  theory
• 1831 at the age of 21 sailed as a naturalist on
  an expedition aboard the Beagle collecting data
  and mapping S. America and the S. Pacific.

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• Darwins Job was to collect , study and store
  Biological specimens.
• In 1835, after leaving South America, the Beagle
  sailed to the Galapagos Islands, about thirteen
  small islands six hundred miles from South
  America, near the Equator.

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• There he saw many unique creatures found only on
  those islands, but similar to those on the
  mainland. Among these were marine iguanas and
  giant tortoises, which Darwin and the Beagle crew
  rode like horses.
• On the Galapagos Islands, Darwin also saw several
  different types of finch, a different species on
  each island.

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• He noticed that each finch species had a
  different type of beak, depending on the food
  available on its island.
• The finches that ate large nuts had strong beaks
  for breaking the nuts open. Finches that ate
  small nuts and seeds had beaks for cracking nuts
  and seeds. Darwin noticed that fruit-eating
  finches had parrot-like beaks, and that finches
  that ate insects had narrow, prying beaks.

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• After observing these differences Darwin wrote
• "One might really fancy that from an original
  paucityscarcity of birds ... one species had
  been taken and modified for different ends."

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Information from http//www.necsi.org/projects/evo
lution/darwin/beagle/darwin_beagle_intro.html

• Later, Darwin concluded that several birds from
  one species of finch had probably been blown by
  storm or otherwise separated to each of the
  islands from one island or from the mainland. The
  finches had to adapt to their new environments
  and food sources. They gradually evolved into
  different species.

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• Darwin returned from his voyage in the Beagle in
  1836, and spent the next 22 years studying his
  collections and conducting experiments.

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Natural Selection

• Natural Selection is the mechanism for change in
  populations that occurs when organisms with
  favorable variations for a particular environment
  survive, reproduce, and pass these variations on
  to their offspring. (Biology the Dynamics of Life)

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Structural Adaptations

• Mimicry- a structural adaptation that provides
  protection for an organism by enabling it to copy
  the appearance of another species.
• Camouflage- enables an organisms to blend with
  its surroundings.

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Physiological Adaptations

• Physiological Adaptations- changes in an
  organisms metabolic processes.
• For example- Many Bacteria have evolved
  adaptations to be resistant to many antibiotic
  medicines which previously killed them.

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Anatomical Studies Indicate Evolutionary
Relationships

• Homologous Structures- similar in structure
  organs which indicate a common evolutionary
  origin.
• Analogous Structures- Any body part that is
  similar in function. Does not indicate any
  evolutionary origin.

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Supporting Evidence of Evolution

• Any organ or body structure that no longer has a
  functioning role is called a vestigial structure.
• Vestigial Structures suggest that the organ or
  body structure had a role an earlier species
  which has subsequently been rendered useless.

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Embryological development

• There is little to no difference among early bird
  and mammal embryos.
• As the embryos mature differences become more
  apparent.
• However, the similarities suggest to scientists
  that both species had a common evolutionary
  origin.

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Genetic Comparisons

• Similar DNA between species is considered to be
  more useful than anatomical studies.
• Similar DNA sequences suggests a common
  evolutionary origin between species.

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Evolutionary Mechanisms

• Evolution is not widely thought to occur to a
  single individual rather slowly as populations of
  a species change over many generations.
• Harvard Paleontologist Stephen J. Gould is one
  dissenter to the thought that Evolution is a slow
  process.

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Punctuated Equilibrium

• Goulds theory proposes that instead of a slow,
  continuous movement evolution tends to be
  characterized by long periods of virtual stand
  still "equilibrium""punctuated" by episodes of
  very fast development of new forms
• http//pespmc1.vub.ac.be/PUNCTUEQ.html

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• Goulds theory states that typical variations
  tend to be small. Therefore, Darwin saw evolution
  as a slow, continuous process, without sudden
  jumps. However, if you study the fossils of
  organisms found in subsequent geological layers,
  you will see long intervals in which nothing
  changed ("equilibrium"), "punctuated" by short,
  revolutionary transitions, in which species
  became extinct and replaced by wholly new forms.

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Darwins Evolution

• The evolution of a new species is called
  speciation
• Speciation can only occur when either
  interbreeding or the production of fertile
  offspring is some how prevented
• This can occur through Physical Barriers

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Geographic Isolation

• Plate Tectonics, volcanic eruptions, violent
  storms etc. all have the capability of isolating
  a population creating Geographic Isolation of
  Species.
• Over Time, Darwin states based upon his
  observations in the Galapagos that each small
  population would adapt to the local environment
• This would eventually change the gene pool and a
  new species could be created.

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• When Geographic Isolation occurs the gene pool is
  closed. Such that species can only breed with
  other species in the same location.
• This is referred to as Reproductive Isolation
  because species that were formerly able to breed
  (Such Galapagos Finch with S. American Finch) are
  prevented from breeding thus no fertile offspring
  will be born.

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Patterns of Evolution

• Adaptive Radiation- This is the type of species
  change that Darwin observed in the Galapagos.
• Adaptive Radiation occurs when an ancestral
  species evolves into an array of species that
  thrive in particular niches.

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Divergent Evolution

• Adaptive Radiation is an example of Divergent
  Evolution.
• Divergent Evolution occurs when species begin to
  adapt to different environmental conditions and
  change becoming less and less similar to the
  ancestral species.

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Convergent Evolution

• Convergent Evolution is when distantly related
  organisms evolve similar traits.
• In certain environments certain adaptations are
  advantageous. Thus, species lacking common
  ancestors may arrive with similar traits.