Darwin _amp; Evolution by Natural Selection

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					                  Darwin & Evolution
                   Natural Selection


                    Insect eaters
                                    Seed eaters

                   Bud eater
Regents Biology                                   2006-2007
   Charles Darwin …
     born into a fairly wealthy family.
     Had a father who was a medical doctor
         and grandfather was Josiah
         Wedgewood (the
        started medical school, but lost
        attended theologian school, but was
         more interested in biology and geology.

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   Charles Darwin
    Proposed a way how
       evolution works
         How did creatures
          change over time?
         by natural selection

     Collected a lot of
       evidence to support
       his ideas
         1809-1882
         British naturalist

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   Darwin’s influences
     Charles Lyell- wrote Principles of
        Geology (1830). Believed in
        uniformitarianism which states that the
        earth was shaped entirely by slow-moving
        forces still in operation today, acting over a
        very long period of time.

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  Thomas Malthus- (1797 )wrote Essay on the
    Principle of Population which argued that
    because of the natural human urge to
    reproduce, human population increases
    geometrically (1, 2, 4, 16, 32, 64, 128, 256,
    etc.). But food supply increases
    arithmetically (1, 2, 3, 4, 5, 6, 7, 8, etc.).
    Therefore, since food is necessary to
    human life, population growth in any area
    or on the planet, if unchecked, would lead
    to starvation.
  Darwin thought, this would apply to plants
    and animals too.
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        Check out the videos.

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   Voyage of the HMS Beagle
    Invited to travel around the world
        1831-1836 (22 years old!)
        makes many observations of nature

             main mission of the Beagle was to chart
              South American coastline

  Robert Fitzroy

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   Voyage of the HMS Beagle
     Stopped in Galapagos Islands
             500 miles off coast of Ecuador

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    Recently formed volcanic
    islands. Most of animals on
    the Galápagos live nowhere
    else in world, but they look
    like species living on South
    American mainland.

Regents Biology                    800 km west of Ecuador
  Darwin found…many unique species

        Many of Darwin’s observations made
                him wonder… Why?

       Darwin asked:
           Why were these creatures found only
           on the Galapagos Islands?
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  Darwin found…clues in the fossils
   Darwin found:
   Evidence that creatures
   have changed over time

                             present day Armadillos

                          Darwin asked:
                          Why should extinct
                          armadillos & modern
                          armadillos be found on
      ancient Armadillo
Regents Biology           same continent?
   Darwin found:
   Different shells on tortoises on different islands

                           Darwin asked:
                      Is there a relationship
                     between the environment
                         & what an animal
                            looks like?

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   Darwin found… birds
     Darwin found:
     Many different birds
     on the Galapagos

     He thought he found Finch?            QuickTime™ and a
                                      Photo - JPEG decompressor

     very different kinds…          are needed to see this picture.

Regents Biology             Woodpecker?                               Warbler?
   But Darwin found… a lot of finches
Darwin was amazed to
find out:
All 14 species of birds
were finches…
But there is only one
species of finch on the   Large ground
                             Finch?                                 Small ground
                                           QuickTime™ and a
                              finch are needed to see this picture.
                                      Photo - JPEG decompressor        finch
mainland!                          Darwin asked:
                               If the Galapagos
                           finches came from the
                           mainland, why are they
                              so different now?
Regents Biology            Warbler finch
                           Woodpecker?                        Tree finch
   The finches cinched it! beaks are
                   different
   Darwin found:           inherited variations
   The differences        serve as adaptations
   between species of
                                      Darwin compete
                           that help birds said:
   finches were
                           for food
   associated with the                  Ahaaaa!
                          these birds survive &
   different food they              A flock of South ground
                           Large ground
                           Big seed eater
                                 Finch?         Small
                                               Small seed eater
   ate.                    reproduce        QuickTime™ and a
                                   American finches
                                finch               finch
                                       Photo - JPEG decompressor
                                     are needed to see this picture.
                          pass on the genes for
                               were stranded on the
                           those more fit beaks
                          over time nature selected
                           for different species with
                           different beaks
Regents Biology              Insect finch
                            Woodpecker?                            Tree finch
                                                                Leaf & bud eater
Relationship between species (beaks) & food

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   Darwin’s finches
     Darwin’s conclusions
             variations in beaks
                differences in beaks in the original flock
                adaptations to foods available on islands
             natural selection for most fit
                over many generations, the finches were
                  selected for specific beaks & behaviors
             offspring inherit successful traits
                accumulation of winning traits:
                  both beaks & behaviors
             separate into different species
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      From 1 species to 14 species…
                             Warbler finch      Cactus finch

          Woodpecker finch                                     Sharp-beaked finch

               Small                                                      Small
      insectivorous                                                       ground
           tree finch                                                     finch
        Large                                Cactus
insectivorous                                 eater                           Medium
    tree finch                                                                ground
                              Insect eaters                                   finch
                                                Seed eaters                         Large
 Vegetarian                                                                         ground
  tree finch                 Bud eater                                              finch

                                 natural selection for best
  Regents Biology                survival & reproduction
   Earlier ideas on Evolution
     LaMarck
           evolution by acquired
              creatures developed
               traits during their lifetime
              give those traits to their
           example
              in reaching higher
                  leaves giraffes stretch
                  their necks & give the
                  acquired longer neck to
           not accepted as valid
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  Darwin’s view of Evolution
   Darwin
      giraffes that already
       have long necks
       survive better
      leave more offspring
       who inherit their long
         variation
         selection &
             reproduction &
              inheritance of
              more fit traits
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    Darwin found… more fossils
     Darwin found:
     Evidence that creatures
     have changed over time
                                 present day Sloth
(extinct) Giant ground sloth
                               Darwin asked:
                               Why should
                               extinct sloths &
                               modern sloths be
                               found on the same
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   Darwin Publishes His Results
     On the Origin of Species By Natural
        Alfred Wallace also came to the same
         conclusions as Darwin and they
         published their results together.

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   Not a lot was known in the 1840s
     the basic mechanism for speciation
         was unknown
        there were (and still are) gaps in the
         fossil record
        little known about genes and inherited
        age of the earth was still disputed
        people believed each species was a
         distinct and unchanging entity.

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   Natural selection was based on the following
     1) Species have great fertility. They make more
      offspring than can grow to adulthood.
     2) Populations remain roughly the same size, with
      modest fluctuations.
     3) Food resources are limited, but are relatively
      constant most of the time.
     From these three observations it may be inferred
      that in such an environment there will be a
      struggle for survival among individuals.
     4) In sexually reproducing species, generally no
      two individuals are identical. Variation is rampant.
     5) Much of this variation is heritable.
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      To summarize Darwin's Theory of Evolution;
        1. Variation: There is Variation in Every
        2. Competition: Organisms Compete for limited
        3. Offspring: Organisms produce more Offspring
        than can survive.
        4. Genetics: Organisms pass Genetic traits on to
        their offspring.
        5. Natural Selection: Those organisms with the
        Most Beneficial Traits are more likely to Survive
        and Reproduce.

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      The End

      Adapted from Regents Biology

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