Evolution by tangshuming


Why is it taught?
            Do you agree…
► Isthere variation within a species?
► Can new variations arise?
► Are there species on earth now that were
  not here long ago?
► Are there species there were here long ago
  that are not here now?
► Can a variation decrease survival chances?
             Do you agree?
► Can a variation increase survival chances?
► Are surviving individuals possibly more
  successful at reproducing healthy offspring?
► Can allele frequencies change in a
► Ifyou have agreed with the past eight
  statements, you agree that evolution

► Now   let’s take a look…
Why on Earth would anyone think of
       this kind of theory?
► Curiosity
► We   share Earth with so many millions of
  other kinds of life.
► Human tendency (built into our wiring) to
  categorize or classify
► Consistent similarities in living things that
  are clearly different as well
► Darwin was intrigued with the diversity of
  life which clearly conflicted with popular
  theory about life on Earth.
How does a hypothesis become a theory?

   Remember a hypothesis must be
    testable for support as well as being
   If the hypothesis continues to be
    supported with more scientists testing
    with modern and numerous observations
    and experiments, the hypothesis is seen
    as a theory of science.
   Isn't Evolution Just a Theory?
    II. A. Who was Charles Darwin?
   Strong desire to understand and explain what he
    could observe in nature.
   Naturally curious – true scientist
   Naturalist – main interests were studying nature
    and collecting a diversity of organisms.
   Recommended for position of naturalist on ship
    called the H.M.S. Beagle. By his professor at
   Reluctant rebel
         Darwin’s Observations
 Most important observations were on the
  Galapagos Islands off the coast of Ecuador.
 Saw similarities and differences among the
  organisms on mainland and the islands (600
  mi. offshore).
 Became curious about origin of different plants
  and animals and variations of species he
  recorded of similar organisms.
 Finches and tortoises most often talked about
  in books, but he observed other animals and
  plants as well.
          Darwin’s observations

 Impressed with how organisms survived
  and produced offspring
 Realized importance of ancient
  organisms in solving puzzle of diversity –
  collected fossils.
 Noticed how well suited the species
  seemed to be for their environments.
Darwin’s Analysis and Conclusions

 While on journey home he started making
  careful study of the specimens he
  collected, and thinking about the patterns
  he was seeing.
 When he got back to Britain, he took 20
  years to carefully develop his theory of
 Published On the Origin of Species in
III. Historical Look at the Theory of
Influence on Darwin

  Maybe as Earth changes, so do forms of
  It would have to take a long time for life
   to change in the way he was inferring.
  Evolution became a revolutionary idea
   that was inspired by these & other
   controversial thinkers.
  Many people found his ideas too
   shocking to accept, and so did he.
Lamarck (1809)

    Theory of acquired traits (transmutation)
      Need – If an organism needs a trait it will
       get the trait through extension of body.
      Use and Disuse – If an organism uses a
       trait it will remain; otherwise it disappears
      Inheriting acquired traits – Traits that the
       parents develop during their life will be
       passed to the children
      Not reasonable in today’s world
               Lamarck’s Evolution Theory
Section 15-2   Acquired Traits
Thomas Malthus (1798)

    Before the writings of Lamarck
    The Principles of Population essay stated
     populations outgrew their food supplies.
    This caused organisms to compete and
     struggle for one species to survive against
    Predicted humans would also outgrow their
     food supply and space on Earth.
    Note: Darwin read this essay.
Alfred Russel Wallace
  Darwin was reluctant to publish his ideas due
   to the controversial nature of what he was
  Alfred Russel Wallace was a fellow naturalist
   who sent Darwin an essay on his own findings
   and theories about competition for resources
   (rings of Malthus) which were very similar to
  This was the final push he needed to publish
   his own findings.
What was Darwin thinking?
  He was always interested in using
   observations and prior knowledge (based on
   reading works of others) to formulate his
  He was not by nature a rebel and trouble
  He was surprised and disturbed by his own
  He was not going to publish his work, but did
   want others to know of his findings.
Beliefs of the time
  Not many people accepted the ideas of
   transmutation (evolution) stated by people like
  People believed in an Earth and life that were
   only thousands of years old.
  Everyone accepted the Earth and all life were
   as they were when created in one original
   creation event; no changes since then.
  When fossils kept popping up, some adjusted
   their beliefs to catastrophic events followed by
   periods of creation.
Darwin’s argument

  People were really already using the
   idea of differences in individuals with
   selective breeding.
  Noted that breeders routinely used
   variation to improve crops and livestock,
   choosing individuals with desired traits to
  Darwin’s term for this – artificial selection
Darwin – Theory of Natural Selection
  – All organisms produce more offspring than can
  – So, members of the species compete for food,
    space and survival (limited resources).
  – Within any population there is variation among the
  – Organisms with the best variations for the
    environment in which they live will survive
  – Nature selects which organisms will survive
  – How Does Evolution Really Work
Evolution / the controversial parts
(descent with modifications)

   Species change over time.
   Species today have descended with
    modifications from species in the past.
   There is a single tree of life.
Concept Map
   Section 15-3

                                         Evidence of


                         Geographic                                       Similarities
  The fossil record    distribution of                                      in early
                                                       body structures
                       living species                                    development

which is composed of   which indicates                  which implies    which implies

      Physical           Common
     remains of          ancestral                     Similar genes     Similar genes
     organisms            species
Evidence for Evolution
Evolution = Change in species over time

  – Fossils – found in sedimentary rock /
    fossil record
  – Geographic Distribution – different
    animals on different continents, but
    similar animals in similar environments
  – Homologous parts – similar in basic
    internal structure but different form and
  – Analogous parts – different body
    structure similar in function; usually in
    same environment
Figure 15–14 Geographic Distribution
of Living Species
 Section 15-3



                     NORTH                 Muskrat
                                 Muskrat   Beaver and



                                           Coypu and
                Capybara         SOUTH

               Figure 15–
Section 15-3
               15 Homologous Body

Turtle              Alligator            Bird   Mammals

                Typical primitive fish
Evidence (cont’d.)

 – Vestigial organs – body
   structure reduced in
   function (next slide)
 – Embryology – similar
   structures in embryos
   develop in same order
 – Genetic comparison –
   similar DNA and
Mechanisms for Evolution
   Populations evolve not single organism
   Populations change
    – Genetic equilibrium – frequency of alleles does
      change from generation to generation
    – Genetic drift – alteration of allelic frequencies by
   Geographic isolation – populations are
    isolated from other areas – island,
   Reproductive isolation – formerly
    interbreeding organisms cannot produce
    fertile offspring
Evolution of
whale from
land dwelling

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