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Chapter 15
                  Lamarck (1801)
   Theory of Acquired Characteristics:
    • An organism changes to adapt to its
      environment and those changes are passed
      on to its offspring.
    • He thought that an organism’s actions
      resulted in changes that could be inherited
      by the next generation
         elephant trunks
         giraffe necks
    • Although his ideas were not correct, Lamarck
      introduced the idea of a scientific explanation
      for evolution. Other scientists began to try
      to explain it.
Charles Darwin (English Naturalist)
   1831 – HMS Beagle
   Collected rock, fossil, plant, and
    animal specimens during the ship’s
    travels to S. America.
   Influenced by:
    • Charles Lyell
    • Malthus
         Who was Charles Lyell?
   Lyell was a geologist who published a
    book that suggested that the Earth was
    millions of years old
    • Before it was thought that Earth was
      thousands of years old
    • Lyell said that the age of the Earth had to be
      judged by events that are happening now,
      earthquakes, volcanic eruptions, floods
          Who was Malthus?
   Malthus was an economist who
    published a book that said that if the
    population of the world continued to
    increase at is current rate, we would
    run out of food and other resources
    • Darwin thought that is that was true of
      humans, it would also be true of nature
Galapagos Islands – a series of volcanic
islands off the coast of Ecuador
       Why were the Galapogos
     Islands important to Darwin?
   Darwin saw organisms that were
    similar to organisms he saw in South
   Darwin saw somewhat similar species
    on each island that were suited to their
    particular environments
    • Darwin’s finches
    • Galapagos Tortoises
What did Darwin observe about
 the finches on the islands?
   Darwin observed that the finches had
    different shaped beaks
   The beaks of the birds were adapted
    to the food in the environment where
    they lived
   Darwin later found out that all the
    birds were related and there were
    similar birds living in South America
           The Origin of Species
   1859 – Darwin put together the evidence
    for natural selection as a mechanism of
    evolution and published The Origin of
    Species (by Means of Natural Selection)
   Main Points:
    • The diverse forms of life have arisen by
      descent with modification from ancestral
    • The mechanism of modification has been
      natural selection working over enormous tracts
      of time.
   Darwin used the term evolution only on
    the last page.
    How did his voyage influence
    his idea of natural selection?
   Darwin observed similar species
    geographically close together
   He observed similar organisms that
    had adapted to different
    • He inferred that the organisms has a
      common ancestor and through natural
      selection had adapted to their
 Principles for Change Over Time:
1. Genetic variations within a population
   are visible.
2. Variations can be inherited.
3. Overpopulation “struggle for
4. Variations that increase reproductive
   success (fitness) will have a greater
   chance of being passed on than those
   that don’t.

   Theory of Natural Selection:
    • Hypothesized that new species could appear
      gradually over time through small changes in
      ancestral species.
          Artificial Selection
   Artificial Selection – Darwin
    realized that the process of artificial
    selection that was used in agriculture
    and breeding of domestic animals
    changed the characteristics of those
    organisms. By selecting the parents
    of the organisms the breeder can
    choose the characteristics of the
         Natural selection
   Natural selection - Darwin inferred
    that the same process could happen
    in nature. The environment selects
    which organisms are best suited and
    those get to produce offspring.
    If given enough time, natural
    selection could modify a population
    enough to produce a new species.
            What is Evolution?
- Any change in the relative frequencies of alleles
  in a population’s gene pool.
- Small changes over a long period of time

- Evolution works on populations not individuals.
- Evolution is CHANGE OVER TIME
     Support for Evolution
1. Fossil Record:
      How does fossil evidence
      support Darwin’s ideas?
   Fossils show that ancient species
    shared similarities with species now
    on Earth
   The fossil evidence is a visual time
    table of how species have changes
    over time

2. Comparative Anatomy - study of similarities and
differences in the anatomy (body plan) of an organism:
  a. Homologous Structures – anatomically similar
      structures inherited from a common ancestor.
  b. Vestigial Structures – structures that are the
      reduced forms of functional structures in other
      organisms. (see Table 15.2, page 425)
  c. Analogous Structures – not inherited through
      common ancestors.
Examples of Vestigial Structures:
                                      The wings of kiwis
                                      are too small to be
                                      of any use in flight.

                  Snake Pelvis

    Appendix                     Snake Pelvis
Examples of Analogous Structures:
Wing of an eagle and the wing
of a beetle have the same
function but are constructed in
different ways from different
3. Comparative Embryology – vertebrae
embryos exhibit homologous structures during
certain phases of development but become
totally different structures in the adult form.
                1. Head
                2. Pharyngeal Pouches
                3. Tail

  Bird Embryo                      Human Embryo
4. Comparative Biochemistry – scientific
    data shows that common ancestry can
    be seen in metabolic molecules that are
 - cytochrome c (see Fig. 15.9, page 427)
 - other proteins, as well
5. Geographic Distribution
  (biogeography)– of plants and animals
  - Darwin observed that animals on the S.
    American mainland were more similar
    to other S. American animals than they
    were to animals living in similar
    environments in Europe.
Ratite Birds
        Patterns of Evolution
1.   Adaptive Radiation
2.   Coevolution
3.   Convergent Evolution
            1. Adaptive Radiation
   Also called divergent evolution
   Can occur in a relatively short period of
   When one species gives rise to many in
    response to the creation of a new habitat
    or another ecological opportunity.
   Differences accumulate between
    populations that result in new species
   Organisms have a common ancestor
   Example =Darwin’s finches
            2. Co-evolution
   Many species evolve in close
    relationship with other species.
   The evolution of one species can
    affect the evolution of another
   Example = comet orchids and the
    moths that pollinate them. The foot-
    long flowers of this plant perfectly
    match the foot-long tongue of the
       3. Convergent Evolution
   When unrelated species evolve
    similar traits even though they live in
    different parts of the world.
   Organisms do not have a common
   Occurs in environments that are
    geographically far apart but that
    have similar ecology and climate.
Example for convergent evolution:
     Why does evolution matter
   www.pbs.org/wgbh/evolution/educat