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Charles Darwin

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He noticed that each finch species had a different type of beak, depending on ... Finches that ate small nuts and seeds had beaks for cracking nuts and seeds. ... – PowerPoint PPT presentation

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Title: Charles Darwin


1
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.

2
  • 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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4
  • 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.

5
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6
  • 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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8
  • 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."

9
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.

10
  • Darwin returned from his voyage in the Beagle in
    1836, and spent the next 22 years studying his
    collections and conducting experiments.

11
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)

12
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.

13
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.

14
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.

15
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.

16
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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18
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.

19
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.

20
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

21
  • 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.

22
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

23
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.

24
  • 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.

25
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.

26
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.

27
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.
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